From 4d49931dfccee1a695206648673919a9a8906e9c Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Tue, 30 May 2023 17:17:22 +0200
Subject: [PATCH 01/23] Highlight non-clojure languages

---
 notebooks/markdown_fences.md           | 31 ++++++++++++++++++++++----
 src/nextjournal/clerk/render/code.cljs | 31 ++++++++++++++++++--------
 2 files changed, 49 insertions(+), 13 deletions(-)

diff --git a/notebooks/markdown_fences.md b/notebooks/markdown_fences.md
index 486beb917..938872537 100644
--- a/notebooks/markdown_fences.md
+++ b/notebooks/markdown_fences.md
@@ -1,27 +1,50 @@
 # 🤺 Markdown Fences
+## Handling Clojure blocks
 
 ```
 '(evaluated :and "highlighted")
 ```
 
+```clj
+'(evaluated :and "highlighted")
+```
+
 ```clojure
 '(evaluated :and "highlighted")
 ```
 
 ```clojure {:nextjournal.clerk/code-listing true}
-'(1 2 "not evaluated" :but-still-highlighted)
+(1 2 "not evaluated" :but-still-highlighted)
 ```
 
-```clojure {:nextjournal.clerk/code-listing true}
-'(1 2 "not evaluated" :but-still-highlighted)
+```{:nextjournal.clerk/code-listing true}
+(1 2 "not evaluated" :but-still-highlighted)
 ```
 
+## 🏳️‍🌈 Polyglot Highlighting
+
+```edn
+(1 2 "not evaluated" :but-still-highlighted)
+```
+
+javascript
+
 ```js
 () => {
   if (true) {
     return 'not evaluated'
   } else {
-    return 'what'
+    return 123
   }
 }
 ```
+
+python
+
+```python
+class Foo(object):
+    def __init__(self):
+        pass
+    def do_this(self):
+        return 1
+```
diff --git a/src/nextjournal/clerk/render/code.cljs b/src/nextjournal/clerk/render/code.cljs
index 82c7242a9..987f59105 100644
--- a/src/nextjournal/clerk/render/code.cljs
+++ b/src/nextjournal/clerk/render/code.cljs
@@ -1,5 +1,5 @@
 (ns nextjournal.clerk.render.code
-  (:require ["@codemirror/language" :refer [HighlightStyle syntaxHighlighting]]
+  (:require ["@codemirror/language" :refer [HighlightStyle syntaxHighlighting LanguageDescription]]
             ["@codemirror/state" :refer [EditorState RangeSetBuilder Text]]
             ["@codemirror/view" :refer [EditorView Decoration]]
             ["@lezer/highlight" :refer [tags highlightTree]]
@@ -7,7 +7,8 @@
             [applied-science.js-interop :as j]
             [clojure.string :as str]
             [nextjournal.clerk.render.hooks :as hooks]
-            [nextjournal.clojure-mode :as clojure-mode]))
+            [nextjournal.clojure-mode :as clojure-mode]
+            [shadow.esm]))
 
 (def highlight-style
   (.define HighlightStyle
@@ -87,10 +88,24 @@
                   (< pos to)
                   (concat [(.sliceString text pos to)]))))))))
 
-(defn lang->deco-range [lang code]
-  (let [builder (RangeSetBuilder.)]
-    (when lang
-      (highlightTree (.. lang -parser (parse code)) highlight-style
+(defn matching-language-parser [language]
+  (if  (= "clojure" language)
+    (js/Promise.resolve (.-parser clojureLanguage))
+    (.. (shadow.esm/dynamic-import "https://cdn.skypack.dev/@codemirror/language-data@6.1.0")
+        (then (fn [mod]
+                (when-some [langs (.-languages mod)]
+                  (when-some [^js matching (or (.matchFilename LanguageDescription langs language)
+                                               (.matchLanguageName LanguageDescription langs language))]
+                    (.load matching)))))
+        (then (fn [lang] (when lang
+                           (js/console.log :found language lang)
+                           (.. lang -language -parser)))))))
+
+(defn lang->deco-range [language code]
+  (let [^js builder (RangeSetBuilder.)
+        ^js parser (hooks/use-promise (matching-language-parser language))]
+    (when parser
+      (highlightTree (.parse parser code) highlight-style
                      (fn [from to style]
                        (.add builder from to (.mark Decoration (j/obj :class style))))))
     (.finish builder)))
@@ -100,9 +115,7 @@
     [:div.cm-editor
      [:cm-scroller
       (into [:div.cm-content.whitespace-pre]
-            (map (partial style-line
-                          ;; TODO: use-promise hook resolving to language data according to @codemirror/language-data
-                          (lang->deco-range (when (= "clojure" language) clojureLanguage) code) text))
+            (map (partial style-line (lang->deco-range language code) text))
             (range 1 (inc (.-lines text))))]]))
 
 ;; editable code viewer

From 16f4206808e34e16f1c174e2f037f1be8d376fc5 Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Tue, 30 May 2023 17:26:41 +0200
Subject: [PATCH 02/23] Match language by filename

---
 notebooks/markdown_fences.md           | 13 ++++++++++++-
 src/nextjournal/clerk/render/code.cljs |  4 ++--
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/notebooks/markdown_fences.md b/notebooks/markdown_fences.md
index 938872537..816a12235 100644
--- a/notebooks/markdown_fences.md
+++ b/notebooks/markdown_fences.md
@@ -41,10 +41,21 @@ javascript
 
 python
 
-```python
+```py
 class Foo(object):
     def __init__(self):
         pass
     def do_this(self):
         return 1
 ```
+
+C++
+
+```c++
+#include <iostream>
+
+int main() {
+    std::cout << "Hello, world!" << std::endl;
+    return 0;
+}
+```
diff --git a/src/nextjournal/clerk/render/code.cljs b/src/nextjournal/clerk/render/code.cljs
index 987f59105..8842779f4 100644
--- a/src/nextjournal/clerk/render/code.cljs
+++ b/src/nextjournal/clerk/render/code.cljs
@@ -94,8 +94,8 @@
     (.. (shadow.esm/dynamic-import "https://cdn.skypack.dev/@codemirror/language-data@6.1.0")
         (then (fn [mod]
                 (when-some [langs (.-languages mod)]
-                  (when-some [^js matching (or (.matchFilename LanguageDescription langs language)
-                                               (.matchLanguageName LanguageDescription langs language))]
+                  (when-some [^js matching (or (.matchLanguageName LanguageDescription langs language)
+                                               (.matchFilename LanguageDescription langs (str "code." language)))]
                     (.load matching)))))
         (then (fn [lang] (when lang
                            (js/console.log :found language lang)

From 5ca7896b3005d38942a90b526e7e13b6b755123a Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Tue, 30 May 2023 17:32:40 +0200
Subject: [PATCH 03/23] Use our parser when possible

---
 notebooks/markdown_fences.md           | 6 ++++--
 src/nextjournal/clerk/render/code.cljs | 2 +-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/notebooks/markdown_fences.md b/notebooks/markdown_fences.md
index 816a12235..0593276da 100644
--- a/notebooks/markdown_fences.md
+++ b/notebooks/markdown_fences.md
@@ -23,11 +23,13 @@
 
 ## 🏳️‍🌈 Polyglot Highlighting
 
+EDN
+
 ```edn
 (1 2 "not evaluated" :but-still-highlighted)
 ```
 
-javascript
+Javascript
 
 ```js
 () => {
@@ -39,7 +41,7 @@ javascript
 }
 ```
 
-python
+Python
 
 ```py
 class Foo(object):
diff --git a/src/nextjournal/clerk/render/code.cljs b/src/nextjournal/clerk/render/code.cljs
index 8842779f4..b915d986a 100644
--- a/src/nextjournal/clerk/render/code.cljs
+++ b/src/nextjournal/clerk/render/code.cljs
@@ -89,7 +89,7 @@
                   (concat [(.sliceString text pos to)]))))))))
 
 (defn matching-language-parser [language]
-  (if  (= "clojure" language)
+  (if  (#{"clojure" "clojurescript" "clj" "cljs" "cljc" "edn"} language)
     (js/Promise.resolve (.-parser clojureLanguage))
     (.. (shadow.esm/dynamic-import "https://cdn.skypack.dev/@codemirror/language-data@6.1.0")
         (then (fn [mod]

From 961e06eafcecdbb6d20d42f25d9890a477875237 Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Tue, 30 May 2023 18:26:33 +0200
Subject: [PATCH 04/23] Normalize language from info string

---
 notebooks/markdown_fences.md      |  8 +++---
 src/nextjournal/clerk/parser.cljc | 45 ++++++++++++++++++++++---------
 2 files changed, 38 insertions(+), 15 deletions(-)

diff --git a/notebooks/markdown_fences.md b/notebooks/markdown_fences.md
index 0593276da..0db548f0a 100644
--- a/notebooks/markdown_fences.md
+++ b/notebooks/markdown_fences.md
@@ -6,17 +6,19 @@
 ```
 
 ```clj
-'(evaluated :and "highlighted")
+'(evaluated :and "highlighted" :language clj)
 ```
 
 ```clojure
-'(evaluated :and "highlighted")
+'(evaluated :and "highlighted" :language clojure)
 ```
 
+Use `{:nextjournal.clerk/code-listing true}` in the fence info to signal that a block should not be evaluated.
+
 ```clojure {:nextjournal.clerk/code-listing true}
 (1 2 "not evaluated" :but-still-highlighted)
 ```
-
+if no language is specified we assume it's a clojure cell
 ```{:nextjournal.clerk/code-listing true}
 (1 2 "not evaluated" :but-still-highlighted)
 ```
diff --git a/src/nextjournal/clerk/parser.cljc b/src/nextjournal/clerk/parser.cljc
index 9e7f6f45d..3766d6026 100644
--- a/src/nextjournal/clerk/parser.cljc
+++ b/src/nextjournal/clerk/parser.cljc
@@ -357,24 +357,45 @@
          :nodes (rest nodes)
          ::md-slice []))
 
-(defn fenced-clojure-code-block? [{:as block :keys [type info language]}]
-  (and (code? block)
-       (or (empty? language)
-           (re-matches #"clj(c?)|clojure" language))
-       (not (:nextjournal.clerk/code-listing (let [parsed (p/parse-string-all (subs info (count language)))]
-                                               (when (n/sexpr-able? parsed)
-                                                 (n/sexpr parsed)))))))
+(defn parse-code-info-string
+  "https://spec.commonmark.org/0.30/#code-fence"
+  [{:as node :keys [info]}]
+  (if-not (code? node)
+    {:eval? false}
+    (try
+      ;; TODO: really?
+      (let [sexprs (n/child-sexprs (p/parse-string-all info))
+            language (some #(and (symbol? %) %) sexprs)
+            metadata (some #(and (map? %) %) sexprs)]
+        {:language (if language (name language) "clojure")
+         :metadata metadata
+         :eval? (and (or (not language) (#{'clojure 'clojurescript 'clj 'cljs 'cljc} language))
+                     (not (:nextjournal.clerk/code-listing metadata)))})
+      (catch #?(:clj Throwable :cljs :default) cause
+        (throw (ex-info "We allow info strings of the following shape:
+```language {map with clerk metadata}
+code
+```" node cause))))))
+
+#_ (parse-code-info-string {:type :heading})
+#_ (parse-code-info-string {:type :code :info "clojure"})
+#_ (parse-code-info-string {:type :code :info " clojure"})
+#_ (parse-code-info-string {:type :code :info "clojure {"})
+#_ (parse-code-info-string {:type :code :info "clojure &@foo !!!"})
+#_ (parse-code-info-string {:type :code :info "clojure {:nextjournal.clerk/code-listing true}"})
+#_ (ex-message *e)
 
 (defn parse-markdown-string [{:as opts :keys [doc?]} s]
   (let [{:as ctx :keys [content]} (parse-markdown (markdown-context) s)]
     (loop [{:as state :keys [nodes] ::keys [md-slice]} {:blocks [] ::md-slice [] :nodes content :md-context ctx}]
       (if-some [node (first nodes)]
         (recur
-         (if (fenced-clojure-code-block? node)
-           (-> state
-               (update :blocks #(cond-> % (seq md-slice) (conj {:type :markdown :doc {:type :doc :content md-slice}})))
-               (parse-markdown-cell opts))
-           (-> state (update :nodes rest) (cond-> doc? (update ::md-slice conj node)))))
+         (let [{:keys [language eval?]} (parse-code-info-string node)]
+           (if eval?
+             (-> state
+                 (update :blocks #(cond-> % (seq md-slice) (conj {:type :markdown :doc {:type :doc :content md-slice}})))
+                 (parse-markdown-cell opts))
+             (-> state (update :nodes rest) (cond-> doc? (update ::md-slice conj (cond-> node language (assoc :language language))))))))
 
         (-> state
             (update :blocks #(cond-> % (seq md-slice) (conj {:type :markdown :doc {:type :doc :content md-slice}})))

From 8e56a5b4cc437e8963239f81827d6d1d7f46f96a Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Tue, 30 May 2023 18:28:15 +0200
Subject: [PATCH 05/23] Docs

---
 src/nextjournal/clerk/builder.clj | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/nextjournal/clerk/builder.clj b/src/nextjournal/clerk/builder.clj
index c64bb3cc6..d7365483b 100644
--- a/src/nextjournal/clerk/builder.clj
+++ b/src/nextjournal/clerk/builder.clj
@@ -20,6 +20,7 @@
   (into ["CHANGELOG.md"
          "README.md"
          "notebooks/markdown.md"
+         "notebooks/markdown_fences.md"
          "notebooks/onwards.md"]
         (map #(str "notebooks/" % ".clj"))
         ["cards"

From 19728844a03c2dfbeedf10159ae3bd8bf4f8fa3d Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Tue, 30 May 2023 18:36:59 +0200
Subject: [PATCH 06/23] Defend

---
 src/nextjournal/clerk/parser.cljc      | 1 +
 src/nextjournal/clerk/render/code.cljs | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/nextjournal/clerk/parser.cljc b/src/nextjournal/clerk/parser.cljc
index 3766d6026..7999adc2e 100644
--- a/src/nextjournal/clerk/parser.cljc
+++ b/src/nextjournal/clerk/parser.cljc
@@ -383,6 +383,7 @@ code
 #_ (parse-code-info-string {:type :code :info "clojure {"})
 #_ (parse-code-info-string {:type :code :info "clojure &@foo !!!"})
 #_ (parse-code-info-string {:type :code :info "clojure {:nextjournal.clerk/code-listing true}"})
+#_ (parse-code-info-string {:type :code :info "{:nextjournal.clerk/code-listing true} c++"})
 #_ (ex-message *e)
 
 (defn parse-markdown-string [{:as opts :keys [doc?]} s]
diff --git a/src/nextjournal/clerk/render/code.cljs b/src/nextjournal/clerk/render/code.cljs
index b915d986a..a9de3db8c 100644
--- a/src/nextjournal/clerk/render/code.cljs
+++ b/src/nextjournal/clerk/render/code.cljs
@@ -99,7 +99,8 @@
                     (.load matching)))))
         (then (fn [lang] (when lang
                            (js/console.log :found language lang)
-                           (.. lang -language -parser)))))))
+                           (.. lang -language -parser))))
+        (catch (fn [err] (js/console.warn err))))))
 
 (defn lang->deco-range [language code]
   (let [^js builder (RangeSetBuilder.)

From b33f7db477fcc54e04967050efe0146886116588 Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Wed, 31 May 2023 09:50:34 +0200
Subject: [PATCH 07/23] Do not eval cljs server-side

---
 src/nextjournal/clerk/parser.cljc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/nextjournal/clerk/parser.cljc b/src/nextjournal/clerk/parser.cljc
index 7999adc2e..7198903db 100644
--- a/src/nextjournal/clerk/parser.cljc
+++ b/src/nextjournal/clerk/parser.cljc
@@ -369,7 +369,7 @@
             metadata (some #(and (map? %) %) sexprs)]
         {:language (if language (name language) "clojure")
          :metadata metadata
-         :eval? (and (or (not language) (#{'clojure 'clojurescript 'clj 'cljs 'cljc} language))
+         :eval? (and (or (not language) (#{'clojure 'clj 'cljc} language))
                      (not (:nextjournal.clerk/code-listing metadata)))})
       (catch #?(:clj Throwable :cljs :default) cause
         (throw (ex-info "We allow info strings of the following shape:

From 4e2fa72101da2fcdfeb3cb7397620e5d40c3b25c Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Wed, 31 May 2023 10:18:20 +0200
Subject: [PATCH 08/23] Handle missing language

---
 notebooks/cherry.clj                   |  9 ++++-----
 src/nextjournal/clerk/render/code.cljs | 14 ++++++++------
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/notebooks/cherry.clj b/notebooks/cherry.clj
index f8960d90e..7d458bd59 100644
--- a/notebooks/cherry.clj
+++ b/notebooks/cherry.clj
@@ -70,11 +70,10 @@
           [:div
            [:div.flex
             [:div.viewer-code.flex-auto.w-80.mb-2 [nextjournal.clerk.render.code/editor !input]]
-            [:button.flex-none.bg-slate-100.mb-2.pl-2.pr-2
-             {:on-click click-handler}
-             "Compile!"]]
-           [:div.bg-slate-50
-            [nextjournal.clerk.render/render-code @!compiled]]
+            [:button.flex-none.rounded-md.border.border-slate-200.bg-slate-100.mb-2.pl-2.pr-2.font-sans
+             {:on-click click-handler} "Compile!"]]
+           [:div.bg-slate-100.p-2.border.border-slate-200
+            [nextjournal.clerk.render/render-code @!compiled {:language "js"}]]
            [nextjournal.clerk.render/inspect
             (try (js/eval @!compiled)
                  (catch :default e e))]])))}
diff --git a/src/nextjournal/clerk/render/code.cljs b/src/nextjournal/clerk/render/code.cljs
index a9de3db8c..bdfdea6d8 100644
--- a/src/nextjournal/clerk/render/code.cljs
+++ b/src/nextjournal/clerk/render/code.cljs
@@ -89,18 +89,20 @@
                   (concat [(.sliceString text pos to)]))))))))
 
 (defn matching-language-parser [language]
-  (if  (#{"clojure" "clojurescript" "clj" "cljs" "cljc" "edn"} language)
+  (cond
+    (not language)
+    (js/Promise.resolve nil)
+    (#{"clojure" "clojurescript" "clj" "cljs" "cljc" "edn"} language)
     (js/Promise.resolve (.-parser clojureLanguage))
+    :else
     (.. (shadow.esm/dynamic-import "https://cdn.skypack.dev/@codemirror/language-data@6.1.0")
-        (then (fn [mod]
+        (then (fn [^js mod]
                 (when-some [langs (.-languages mod)]
                   (when-some [^js matching (or (.matchLanguageName LanguageDescription langs language)
                                                (.matchFilename LanguageDescription langs (str "code." language)))]
                     (.load matching)))))
-        (then (fn [lang] (when lang
-                           (js/console.log :found language lang)
-                           (.. lang -language -parser))))
-        (catch (fn [err] (js/console.warn err))))))
+        (then (fn [^js lang-support] (when lang-support (.. lang-support -language -parser))))
+        (catch (fn [err] (js/console.warn (str "Cannot load language parser for: " language) err))))))
 
 (defn lang->deco-range [language code]
   (let [^js builder (RangeSetBuilder.)

From 18385627f9dcfbef51027584d0535cbf0c610e35 Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Wed, 31 May 2023 10:32:23 +0200
Subject: [PATCH 09/23] Fix highlighting for folded code viewer

---
 src/nextjournal/clerk/render.cljs | 6 +++---
 src/nextjournal/clerk/viewer.cljc | 3 +--
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/src/nextjournal/clerk/render.cljs b/src/nextjournal/clerk/render.cljs
index e8bb70bb8..a3cd938fd 100644
--- a/src/nextjournal/clerk/render.cljs
+++ b/src/nextjournal/clerk/render.cljs
@@ -917,9 +917,9 @@
 
 (defn render-code-block [code-string {:as opts :keys [id]}]
   [:div.viewer.code-viewer.w-full.max-w-wide {:data-block-id id}
-   [code/render-code code-string opts]])
+   [code/render-code code-string (assoc opts :language "clojure")]])
 
-(defn render-folded-code-block [code-string {:keys [id]}]
+(defn render-folded-code-block [code-string {:as opts :keys [id]}]
   (let [!hidden? (hooks/use-state true)]
     (if @!hidden?
       [:div.relative.pl-12.font-sans.text-slate-400.cursor-pointer.flex.overflow-y-hidden.group
@@ -952,7 +952,7 @@
          {:class "text-[10px]"}
          "evaluated in 0.2s"]]
        [:div.code-viewer.mb-2.relative.code-viewer.w-full.max-w-wide {:data-block-id id :style {:margin-top 0}}
-        [render-code code-string]]])))
+        [render-code code-string (assoc opts :language "clojure")]]])))
 
 
 (defn url-for [{:as src :keys [blob-id]}]
diff --git a/src/nextjournal/clerk/viewer.cljc b/src/nextjournal/clerk/viewer.cljc
index 5512c55dc..af52b25f4 100644
--- a/src/nextjournal/clerk/viewer.cljc
+++ b/src/nextjournal/clerk/viewer.cljc
@@ -598,8 +598,7 @@
               code?
               (conj (with-viewer (if fold? `folded-code-block-viewer `code-block-viewer)
                       {:nextjournal/opts (assoc (select-keys cell [:loc])
-                                                :id (processed-block-id (str id "-code"))
-                                                :language "clojure")}
+                                                :id (processed-block-id (str id "-code")))}
                       (dissoc cell :result)))
               (or result? eval?)
               (conj (cond-> (ensure-wrapped (-> cell (assoc ::doc doc) (set/rename-keys {:result ::result})))

From 65bcc9bd98f82d43acdb9b0344c638d797177c4a Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Wed, 31 May 2023 10:38:32 +0200
Subject: [PATCH 10/23] Allow to pass language to code-viewer, default to clj

---
 notebooks/viewers/code.clj        | 16 ++++++++++++++++
 src/nextjournal/clerk/viewer.cljc |  6 +++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/notebooks/viewers/code.clj b/notebooks/viewers/code.clj
index ee0f5e7cb..e3648b7c2 100644
--- a/notebooks/viewers/code.clj
+++ b/notebooks/viewers/code.clj
@@ -36,6 +36,22 @@ with     quite
                 some
    whitespace      ")
 
+;; Code in some other language, say Rust:
+(clerk/code {::clerk/opts {:language "rust"}}
+  "fn calculate_factorial(n: u32, result: &mut u32) {
+    if n == 0 {
+        *result = 1;
+    } else {
+        *result = n * calculate_factorial(n - 1, result);
+    }
+}
+fn main() {
+    let number = 5;
+    let mut result = 0;
+    calculate_factorial(number, &mut result);
+    println!(\"The factorial of {} is: {}\", number, result);
+}")
+
 ;; Editable code viewer
 (clerk/with-viewer
   '(fn [code-str _] [:div.viewer-code [nextjournal.clerk.render.code/editor (reagent.core/atom code-str)]])
diff --git a/src/nextjournal/clerk/viewer.cljc b/src/nextjournal/clerk/viewer.cljc
index af52b25f4..fba8bdac1 100644
--- a/src/nextjournal/clerk/viewer.cljc
+++ b/src/nextjournal/clerk/viewer.cljc
@@ -913,7 +913,11 @@
                                               (with-md-viewer)))})
 
 (def code-viewer
-  {:name `code-viewer :render-fn 'nextjournal.clerk.render/render-code :transform-fn (comp mark-presented (update-val (fn [v] (if (string? v) v (str/trim (with-out-str (pprint/pprint v)))))))})
+  {:name `code-viewer
+   :render-fn 'nextjournal.clerk.render/render-code
+   :transform-fn (comp mark-presented
+                       #(update-in % [:nextjournal/opts :language] (fn [lang] (or lang "clojure")))
+                       (update-val (fn [v] (if (string? v) v (str/trim (with-out-str (pprint/pprint v)))))))})
 
 (def reagent-viewer
   {:name `reagent-viewer :render-fn 'nextjournal.clerk.render/render-reagent :transform-fn mark-presented})

From df5c45889e01d2067e635df409186ddca3b6a1ce Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Wed, 31 May 2023 10:58:26 +0200
Subject: [PATCH 11/23] More examples

---
 notebooks/viewers/markdown.clj | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/notebooks/viewers/markdown.clj b/notebooks/viewers/markdown.clj
index cf3133953..db7d10bbc 100644
--- a/notebooks/viewers/markdown.clj
+++ b/notebooks/viewers/markdown.clj
@@ -33,8 +33,8 @@ It's [Markdown](https://daringfireball.net/projects/markdown/), like you know it
 ;; > — Special Forms
 
 ;; ## Code Listings
-
-;; ```
+;; Clojure
+;; ```clj
 ;; {:name :code,
 ;;  :render-fn 'nextjournal.clerk.render/render-code,
 ;;  :transform-fn
@@ -45,7 +45,19 @@ It's [Markdown](https://daringfireball.net/projects/markdown/), like you know it
 ;;      [v]
 ;;      (if (string? v) v (str/trim (with-out-str (pprint/pprint v)))))))}
 ;; ```
-
+;; APL
+;; ```apl
+;; numbers ← 1 2 3 4 5
+;; sum ← 0
+;; n ← ≢numbers  ⍝ Get the number of elements in the array
+;;
+;; :For i :In ⍳n
+;; sum ← sum + numbers[i]
+;; :End
+;;
+;; sum
+;; ```
+;;
 ;; ## Soft vs. Hard Line Breaks
 ;; This one ⇥
 ;; ⇤ is a [soft break](https://spec.commonmark.org/0.30/#soft-line-breaks) and is rendered as a space.

From 5787474992c85687ab55f4e9e4d10a93cd3b6607 Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Wed, 31 May 2023 11:08:08 +0200
Subject: [PATCH 12/23] Parse fail example

---
 src/nextjournal/clerk/parser.cljc | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/nextjournal/clerk/parser.cljc b/src/nextjournal/clerk/parser.cljc
index 7198903db..b7f80b72d 100644
--- a/src/nextjournal/clerk/parser.cljc
+++ b/src/nextjournal/clerk/parser.cljc
@@ -381,6 +381,8 @@ code
 #_ (parse-code-info-string {:type :code :info "clojure"})
 #_ (parse-code-info-string {:type :code :info " clojure"})
 #_ (parse-code-info-string {:type :code :info "clojure {"})
+#_ (parse-code-info-string {:type :code :info "{r, eval=FALSE}"}) ;; RMarkdown/Knitr
+#_ (parse-code-info-string {:type :code :info "{r, eval=FALSE, include=TRUE}"}) ;; RMarkdown/Knitr (failing)
 #_ (parse-code-info-string {:type :code :info "clojure &@foo !!!"})
 #_ (parse-code-info-string {:type :code :info "clojure {:nextjournal.clerk/code-listing true}"})
 #_ (parse-code-info-string {:type :code :info "{:nextjournal.clerk/code-listing true} c++"})

From eb4b66fb25fce19feb53fa3ddae91dda88eb34b0 Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Thu, 1 Jun 2023 12:12:09 +0200
Subject: [PATCH 13/23] Move language clojure/SSR switch at component level

---
 src/nextjournal/clerk/render/code.cljs | 38 ++++++++++++++++++--------
 1 file changed, 26 insertions(+), 12 deletions(-)

diff --git a/src/nextjournal/clerk/render/code.cljs b/src/nextjournal/clerk/render/code.cljs
index bdfdea6d8..b2af36b1e 100644
--- a/src/nextjournal/clerk/render/code.cljs
+++ b/src/nextjournal/clerk/render/code.cljs
@@ -104,22 +104,36 @@
         (then (fn [^js lang-support] (when lang-support (.. lang-support -language -parser))))
         (catch (fn [err] (js/console.warn (str "Cannot load language parser for: " language) err))))))
 
-(defn lang->deco-range [language code]
+(defn add-style-ranges! [range-builder syntax-tree]
+  (highlightTree syntax-tree highlight-style
+                 (fn [from to style]
+                   (.add range-builder from to (.mark Decoration (j/obj :class style))))))
+
+(defn clojure-style-rangeset [code]
+  (.finish (doto (RangeSetBuilder.)
+             (add-style-ranges! (.. ^js clojureLanguage -parser (parse code))))))
+
+(defn syntax-highlight [{:keys [code style-rangeset]}]
+  (let [text (.of Text (.split code "\n"))]
+    (into [:div.cm-content.whitespace-pre]
+          (map (partial style-line style-rangeset text))
+          (range 1 (inc (.-lines text))))))
+
+(defn highlight-clojure [{:keys [code]}]
+  [syntax-highlight {:code code :style-rangeset (clojure-style-rangeset code)}])
+
+(defn highlight-language [{:keys [code language]}]
   (let [^js builder (RangeSetBuilder.)
         ^js parser (hooks/use-promise (matching-language-parser language))]
-    (when parser
-      (highlightTree (.parse parser code) highlight-style
-                     (fn [from to style]
-                       (.add builder from to (.mark Decoration (j/obj :class style))))))
-    (.finish builder)))
+    (when parser (add-style-ranges! builder (.parse parser code)))
+    [syntax-highlight {:code code :style-rangeset (.finish builder)}]))
 
 (defn render-code [^String code {:keys [language]}]
-  (let [text (.of Text (.split code "\n"))]
-    [:div.cm-editor
-     [:cm-scroller
-      (into [:div.cm-content.whitespace-pre]
-            (map (partial style-line (lang->deco-range language code) text))
-            (range 1 (inc (.-lines text))))]]))
+  [:div.cm-editor
+   [:cm-scroller
+    (if (#{"clojure" "clojurescript" "clj" "cljs" "cljc" "edn"} language)
+      [highlight-clojure {:code code}]
+      [highlight-language {:code code :language language}])]])
 
 ;; editable code viewer
 (def theme

From 613f4d994ba784ff7d0ab3a564507a3fa336875e Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Thu, 1 Jun 2023 12:26:37 +0200
Subject: [PATCH 14/23] Naming

---
 src/nextjournal/clerk/render/code.cljs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/nextjournal/clerk/render/code.cljs b/src/nextjournal/clerk/render/code.cljs
index b2af36b1e..7cf8dce96 100644
--- a/src/nextjournal/clerk/render/code.cljs
+++ b/src/nextjournal/clerk/render/code.cljs
@@ -122,7 +122,7 @@
 (defn highlight-clojure [{:keys [code]}]
   [syntax-highlight {:code code :style-rangeset (clojure-style-rangeset code)}])
 
-(defn highlight-language [{:keys [code language]}]
+(defn highlight-imported-language [{:keys [code language]}]
   (let [^js builder (RangeSetBuilder.)
         ^js parser (hooks/use-promise (matching-language-parser language))]
     (when parser (add-style-ranges! builder (.parse parser code)))
@@ -133,7 +133,7 @@
    [:cm-scroller
     (if (#{"clojure" "clojurescript" "clj" "cljs" "cljc" "edn"} language)
       [highlight-clojure {:code code}]
-      [highlight-language {:code code :language language}])]])
+      [highlight-imported-language {:code code :language language}])]])
 
 ;; editable code viewer
 (def theme

From a68a03949c43e05b7a43b6ed7d3cf377cf9d5bf3 Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Thu, 1 Jun 2023 12:28:22 +0200
Subject: [PATCH 15/23] Naming

---
 src/nextjournal/clerk/render/code.cljs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/nextjournal/clerk/render/code.cljs b/src/nextjournal/clerk/render/code.cljs
index 7cf8dce96..270ae59da 100644
--- a/src/nextjournal/clerk/render/code.cljs
+++ b/src/nextjournal/clerk/render/code.cljs
@@ -88,7 +88,7 @@
                   (< pos to)
                   (concat [(.sliceString text pos to)]))))))))
 
-(defn matching-language-parser [language]
+(defn import-matching-language-parser [language]
   (cond
     (not language)
     (js/Promise.resolve nil)
@@ -124,7 +124,7 @@
 
 (defn highlight-imported-language [{:keys [code language]}]
   (let [^js builder (RangeSetBuilder.)
-        ^js parser (hooks/use-promise (matching-language-parser language))]
+        ^js parser (hooks/use-promise (import-matching-language-parser language))]
     (when parser (add-style-ranges! builder (.parse parser code)))
     [syntax-highlight {:code code :style-rangeset (.finish builder)}]))
 

From 7eaf1d7e5f0cd306ac8101ec1dd89ac4798e82b0 Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Thu, 1 Jun 2023 12:30:54 +0200
Subject: [PATCH 16/23] Cleanup

---
 src/nextjournal/clerk/render/code.cljs | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/src/nextjournal/clerk/render/code.cljs b/src/nextjournal/clerk/render/code.cljs
index 270ae59da..040d41048 100644
--- a/src/nextjournal/clerk/render/code.cljs
+++ b/src/nextjournal/clerk/render/code.cljs
@@ -89,12 +89,8 @@
                   (concat [(.sliceString text pos to)]))))))))
 
 (defn import-matching-language-parser [language]
-  (cond
-    (not language)
+  (if (not language)
     (js/Promise.resolve nil)
-    (#{"clojure" "clojurescript" "clj" "cljs" "cljc" "edn"} language)
-    (js/Promise.resolve (.-parser clojureLanguage))
-    :else
     (.. (shadow.esm/dynamic-import "https://cdn.skypack.dev/@codemirror/language-data@6.1.0")
         (then (fn [^js mod]
                 (when-some [langs (.-languages mod)]

From 59a589823f4d13ea0eab75b546654d0facd14c80 Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Thu, 1 Jun 2023 12:46:18 +0200
Subject: [PATCH 17/23] Lift control

---
 src/nextjournal/clerk/render/code.cljs | 31 +++++++++++++-------------
 1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/src/nextjournal/clerk/render/code.cljs b/src/nextjournal/clerk/render/code.cljs
index 040d41048..097e0bfe1 100644
--- a/src/nextjournal/clerk/render/code.cljs
+++ b/src/nextjournal/clerk/render/code.cljs
@@ -1,6 +1,6 @@
 (ns nextjournal.clerk.render.code
   (:require ["@codemirror/language" :refer [HighlightStyle syntaxHighlighting LanguageDescription]]
-            ["@codemirror/state" :refer [EditorState RangeSetBuilder Text]]
+            ["@codemirror/state" :refer [EditorState RangeSet RangeSetBuilder Text]]
             ["@codemirror/view" :refer [EditorView Decoration]]
             ["@lezer/highlight" :refer [tags highlightTree]]
             ["@nextjournal/lang-clojure" :refer [clojureLanguage]]
@@ -89,16 +89,14 @@
                   (concat [(.sliceString text pos to)]))))))))
 
 (defn import-matching-language-parser [language]
-  (if (not language)
-    (js/Promise.resolve nil)
-    (.. (shadow.esm/dynamic-import "https://cdn.skypack.dev/@codemirror/language-data@6.1.0")
-        (then (fn [^js mod]
-                (when-some [langs (.-languages mod)]
-                  (when-some [^js matching (or (.matchLanguageName LanguageDescription langs language)
-                                               (.matchFilename LanguageDescription langs (str "code." language)))]
-                    (.load matching)))))
-        (then (fn [^js lang-support] (when lang-support (.. lang-support -language -parser))))
-        (catch (fn [err] (js/console.warn (str "Cannot load language parser for: " language) err))))))
+  (.. (shadow.esm/dynamic-import "https://cdn.skypack.dev/@codemirror/language-data@6.1.0")
+      (then (fn [^js mod]
+              (when-some [langs (.-languages mod)]
+                (when-some [^js matching (or (.matchLanguageName LanguageDescription langs language)
+                                             (.matchFilename LanguageDescription langs (str "code." language)))]
+                  (.load matching)))))
+      (then (fn [^js lang-support] (when lang-support (.. lang-support -language -parser))))
+      (catch (fn [err] (js/console.warn (str "Cannot load language parser for: " language) err)))))
 
 (defn add-style-ranges! [range-builder syntax-tree]
   (highlightTree syntax-tree highlight-style
@@ -115,9 +113,6 @@
           (map (partial style-line style-rangeset text))
           (range 1 (inc (.-lines text))))))
 
-(defn highlight-clojure [{:keys [code]}]
-  [syntax-highlight {:code code :style-rangeset (clojure-style-rangeset code)}])
-
 (defn highlight-imported-language [{:keys [code language]}]
   (let [^js builder (RangeSetBuilder.)
         ^js parser (hooks/use-promise (import-matching-language-parser language))]
@@ -127,8 +122,12 @@
 (defn render-code [^String code {:keys [language]}]
   [:div.cm-editor
    [:cm-scroller
-    (if (#{"clojure" "clojurescript" "clj" "cljs" "cljc" "edn"} language)
-      [highlight-clojure {:code code}]
+    (cond
+      (not language)
+      [syntax-highlight {:code code :style-rangeset (.-empty RangeSet)}]
+      (#{"clojure" "clojurescript" "clj" "cljs" "cljc" "edn"} language)
+      [syntax-highlight {:code code :style-rangeset (clojure-style-rangeset code)}]
+      :else
       [highlight-imported-language {:code code :language language}])]])
 
 ;; editable code viewer

From 030af3bf55daaebe5302a86f0e06580f94dc338e Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Thu, 1 Jun 2023 14:26:14 +0200
Subject: [PATCH 18/23] Changelog

---
 CHANGELOG.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ddc5f9ff3..9a940780b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -42,6 +42,8 @@ Changes can be:
 
 * 💫 Support non-evaluated clojure code listings in markdown documents by specifying `{:nextjournal.clerk/code-listing true}` after the language ([#482](https://github.com/nextjournal/clerk/issues/482)).
 
+* 🏳️‍🌈 Syntax highlighting for code listings in all [languages supported by codemirror](https://github.com/codemirror/language-data) ([#500](https://github.com/nextjournal/clerk/issues/500)).
+
 * 🐜 Turn off analyzer pass for validation of `:type` tags, fixes [#488](https://github.com/nextjournal/clerk/issues/488) @craig-latacora
 
 * 🐜 Strip `:type` metadata from forms before printing them to hash, fixes [#489](https://github.com/nextjournal/clerk/issues/489) @craig-latacora

From a0176a5087aaab502fd68a1c39b3766707cc4f50 Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Thu, 1 Jun 2023 14:54:21 +0200
Subject: [PATCH 19/23] Assign languages in book

---
 book.clj | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/book.clj b/book.clj
index 307957789..961f52cdc 100644
--- a/book.clj
+++ b/book.clj
@@ -95,7 +95,7 @@
 
 ;; In Emacs, add the following to your config:
 
-;; ```elisp
+;; ```el
 ;; (defun clerk-show ()
 ;;   (interactive)
 ;;   (when-let
@@ -121,7 +121,7 @@
 
 ;; With [neovim](https://neovim.io/) + [conjure](https://github.com/Olical/conjure/) one can use the following vimscript function to save the file and show it with Clerk:
 
-;; ```
+;; ```vimscript
 ;; function! ClerkShow()
 ;; exe "w"
 ;; exe "ConjureEval (nextjournal.clerk/show! \"" . expand("%:p") . "\")"

From dbfbab567e595e62f29658912141f7c72e3d593b Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Thu, 1 Jun 2023 15:01:15 +0200
Subject: [PATCH 20/23] Default to clojure highlighting in indented code blocks

---
 notebooks/markdown_fences.md      | 5 +++--
 src/nextjournal/clerk/viewer.cljc | 2 +-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/notebooks/markdown_fences.md b/notebooks/markdown_fences.md
index 06a4f431c..bb9ae4bcc 100644
--- a/notebooks/markdown_fences.md
+++ b/notebooks/markdown_fences.md
@@ -64,9 +64,10 @@ int main() {
 }
 ```
 
-## [Indented Code Blocks](https://spec.commonmark.org/0.30/#indented-code-blocks) should not be highlighted
+## Indented Code Blocks
+[Indented code blocks](https://spec.commonmark.org/0.30/#indented-code-blocks) default to clojure highlighting
 
     (no (off) :fence)
-    (not "highlighted")
+    (but "highlighted")
 
 fin.
diff --git a/src/nextjournal/clerk/viewer.cljc b/src/nextjournal/clerk/viewer.cljc
index fba8bdac1..052ee43d2 100644
--- a/src/nextjournal/clerk/viewer.cljc
+++ b/src/nextjournal/clerk/viewer.cljc
@@ -707,7 +707,7 @@
     :transform-fn (update-val #(with-viewer `html-viewer
                                  [:div.code-viewer.code-listing
                                   (with-viewer `code-viewer
-                                    {:nextjournal/opts (select-keys % [:language])}
+                                    {:nextjournal/opts {:language (:language % "clojure")}}
                                     (str/trim-newline (md.transform/->text %)))]))}
 
    ;; marks

From 469c7ee5ed2576bac9c98c064e5aadb9ad0395b6 Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Thu, 1 Jun 2023 15:19:53 +0200
Subject: [PATCH 21/23] Document language option for the code viewer

---
 book.clj | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/book.clj b/book.clj
index 961f52cdc..17f4c86c2 100644
--- a/book.clj
+++ b/book.clj
@@ -251,7 +251,7 @@
 
 ;; ### 🎼 Code
 
-;; The code viewer uses
+;; By default the code viewer uses
 ;; [clojure-mode](https://nextjournal.github.io/clojure-mode/) for
 ;; syntax highlighting.
 (clerk/code (macroexpand '(when test
@@ -262,6 +262,21 @@
 
 (clerk/code "(defn my-fn\n  \"This is a Doc String\"\n  [args]\n  42)")
 
+;; You might specify different langauges via `::clerk/opts` like so
+(clerk/code {::clerk/opts {:language "python"}} "
+class Foo(object):
+    def __init__(self):
+        pass
+    def do_this(self):
+        return 1")
+
+(clerk/code {::clerk/opts {:language "c++"}} "
+#include <iostream>
+int main() {
+    std::cout << \" Hello, world! \" << std::endl
+    return 0
+}")
+
 ;; ### 🏞 Images
 
 ;; Clerk now has built-in support for the

From 0b8b316179d249f1953b1fed7225fc7aaa003317 Mon Sep 17 00:00:00 2001
From: Martin Kavalar <martin@nextjournal.com>
Date: Fri, 2 Jun 2023 10:36:25 +0200
Subject: [PATCH 22/23] Tweak prose

---
 book.clj | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/book.clj b/book.clj
index 17f4c86c2..fa2082f34 100644
--- a/book.clj
+++ b/book.clj
@@ -262,7 +262,7 @@
 
 (clerk/code "(defn my-fn\n  \"This is a Doc String\"\n  [args]\n  42)")
 
-;; You might specify different langauges via `::clerk/opts` like so
+;; You can specify the language for syntax highlighting via `::clerk/opts`.
 (clerk/code {::clerk/opts {:language "python"}} "
 class Foo(object):
     def __init__(self):
@@ -270,12 +270,15 @@ class Foo(object):
     def do_this(self):
         return 1")
 
-(clerk/code {::clerk/opts {:language "c++"}} "
+;; Or use a code fence with a language in a markdown.
+
+(clerk/md "```c++
 #include <iostream>
 int main() {
     std::cout << \" Hello, world! \" << std::endl
     return 0
-}")
+}
+```")
 
 ;; ### 🏞 Images
 

From 19f5a877d813cd946e69ba356f374a89e66b87d1 Mon Sep 17 00:00:00 2001
From: Andrea Amantini <lo.zampino@gmail.com>
Date: Fri, 2 Jun 2023 17:28:27 +0200
Subject: [PATCH 23/23] Simplify

---
 notebooks/markdown_fences.md      |  4 ---
 src/nextjournal/clerk/parser.cljc | 56 ++++++++++---------------------
 2 files changed, 18 insertions(+), 42 deletions(-)

diff --git a/notebooks/markdown_fences.md b/notebooks/markdown_fences.md
index bb9ae4bcc..a8335059c 100644
--- a/notebooks/markdown_fences.md
+++ b/notebooks/markdown_fences.md
@@ -18,10 +18,6 @@ Use `{:nextjournal.clerk/code-listing true}` in the fence info to signal that a
 ```clojure {:nextjournal.clerk/code-listing true}
 (1 2 "not evaluated" :but-still-highlighted)
 ```
-if no language is specified we assume it's a clojure cell
-```{:nextjournal.clerk/code-listing true}
-(1 2 "not evaluated" :but-still-highlighted)
-```
 
 ## 🏳️‍🌈 Polyglot Highlighting
 
diff --git a/src/nextjournal/clerk/parser.cljc b/src/nextjournal/clerk/parser.cljc
index 8bab7c653..1699df4f2 100644
--- a/src/nextjournal/clerk/parser.cljc
+++ b/src/nextjournal/clerk/parser.cljc
@@ -357,50 +357,30 @@
          :nodes (rest nodes)
          ::md-slice []))
 
-(defn parse-code-info-string
-  "https://spec.commonmark.org/0.30/#code-fence"
-  [{:as node :keys [info]}]
-  (if-not (and (code? node) info)
-    {:eval? false}
-    (try
-      (let [sexprs (n/child-sexprs (p/parse-string-all info))
-            language (some #(and (symbol? %) %) sexprs)
-            metadata (some #(and (map? %) %) sexprs)]
-        {:language (if language (name language) "clojure")
-         :metadata metadata
-         :eval? (and (or (not language) (#{'clojure 'clj 'cljc} language))
-                     (not (:nextjournal.clerk/code-listing metadata)))})
-      (catch #?(:clj Throwable :cljs :default) cause
-        (throw (ex-info "We allow info strings of the following shape:
-```language {map with clerk metadata}
-code
-```" node cause))))))
-
-#_ (parse-code-info-string {:type :heading})
-#_ (parse-code-info-string {:type :code :info "clojure"})
-#_ (parse-code-info-string {:type :code :info " clojure"})
-#_ (parse-code-info-string {:type :code :info "clojure {"})
-#_ (parse-code-info-string {:type :code :info "{r, eval=FALSE}"}) ;; RMarkdown/Knitr
-#_ (parse-code-info-string {:type :code :info "{r, eval=FALSE, include=TRUE}"}) ;; RMarkdown/Knitr (failing)
-#_ (parse-code-info-string {:type :code :info "clojure &@foo !!!"})
-#_ (parse-code-info-string {:type :code :info "clojure {:nextjournal.clerk/code-listing true}"})
-#_ (parse-code-info-string {:type :code :info "{:nextjournal.clerk/code-listing true} c++"})
-#_ (ex-message *e)
+(defn runnable-code-block? [{:as block :keys [info language]}]
+  (and (code? block)
+       info
+       (or (empty? language)
+           (re-matches #"clj(c?)|clojure" language))
+       (not (:nextjournal.clerk/code-listing
+             (when-some [parsed (when (and (seq language) (str/starts-with? info language))
+                                  (p/parse-string-all (subs info (count language))))]
+               (when (n/sexpr-able? parsed)
+                 (n/sexpr parsed)))))))
+
+#_(runnable-code-block? {:type :code :language "clojure" :info "clojure"})
+#_(runnable-code-block? {:type :code :language "clojure" :info "clojure {:nextjournal.clerk/code-listing true}"})
 
 (defn parse-markdown-string [{:as opts :keys [doc?]} s]
   (let [{:as ctx :keys [content]} (parse-markdown (markdown-context) s)]
     (loop [{:as state :keys [nodes] ::keys [md-slice]} {:blocks [] ::md-slice [] :nodes content :md-context ctx}]
       (if-some [node (first nodes)]
         (recur
-         (let [{:keys [language eval? _metadata]} (parse-code-info-string node)]
-           (if eval?
-             (-> state
-                 (update :blocks #(cond-> % (seq md-slice) (conj {:type :markdown :doc {:type :doc :content md-slice}})))
-                 (parse-markdown-cell opts))
-             (-> state
-                 (update :nodes rest)
-                 (cond-> doc? (update ::md-slice conj
-                                      (cond-> node language (assoc :language language))))))))
+         (if (runnable-code-block? node)
+           (-> state
+               (update :blocks #(cond-> % (seq md-slice) (conj {:type :markdown :doc {:type :doc :content md-slice}})))
+               (parse-markdown-cell opts))
+           (-> state (update :nodes rest) (cond-> doc? (update ::md-slice conj node)))))
 
         (-> state
             (update :blocks #(cond-> % (seq md-slice) (conj {:type :markdown :doc {:type :doc :content md-slice}})))