Auto-generate store documentation

doc/manual/generate-manpage.nix

@@ -1,4 +1,4 @@
-{ toplevel }:
+cliDumpStr:
 
 with builtins;
 with import ./utils.nix;
@@ -63,7 +63,10 @@ let
         * [`${command} ${name}`](./${appendName filename name}.md) - ${subcmd.description}
       '';
 
-      maybeDocumentation = if details ? doc then details.doc else "";
+      maybeDocumentation =
+        if details ? doc
+        then replaceStrings ["@stores@"] [storeDocs] details.doc
+        else "";
 
       maybeOptions = if details.flags == {} then "" else ''
         # Options
@@ -110,18 +113,32 @@ let
       };
     in [ cmd ] ++ concatMap subcommand (attrNames details.commands or {});
 
-  parsedToplevel = builtins.fromJSON toplevel;
+  cliDump = builtins.fromJSON cliDumpStr;
 
   manpages = processCommand {
     command = "nix";
-    details = parsedToplevel;
+    details = cliDump.args;
     filename = "nix";
-    toplevel = parsedToplevel;
+    toplevel = cliDump.args;
   };
 
   tableOfContents = let
     showEntry = page:
       "    - [${page.command}](command-ref/new-cli/${page.name})";
     in concatStringsSep "\n" (map showEntry manpages) + "\n";
 
+  storeDocs =
+    let
+      showStore = name: { settings, doc }:
+        ''
+          ## ${name}
+
+          ${doc}
+
+          **Settings**:
+
+          ${showSettings false settings}
+        '';
+    in concatStrings (attrValues (mapAttrs showStore cliDump.stores));
+
 in (listToAttrs manpages) // { "SUMMARY.md" = tableOfContents; }

doc/manual/local.mk

@@ -60,17 +60,17 @@ $(d)/src/SUMMARY.md: $(d)/src/SUMMARY.md.in $(d)/src/command-ref/new-cli
 	@$(call process-includes,$@,$@)
 
 $(d)/src/command-ref/new-cli: $(d)/nix.json $(d)/generate-manpage.nix $(bindir)/nix
-	@rm -rf $@
-	$(trace-gen) $(nix-eval) --write-to $@.tmp --expr 'import doc/manual/generate-manpage.nix { toplevel = builtins.readFile $<; }'
+	@rm -rf $@ $@.tmp
+	$(trace-gen) $(nix-eval) --write-to $@.tmp --expr 'import doc/manual/generate-manpage.nix (builtins.readFile $<)'
 	@mv $@.tmp $@
 
-$(d)/src/command-ref/conf-file.md: $(d)/conf-file.json $(d)/generate-options.nix $(d)/src/command-ref/conf-file-prefix.md $(bindir)/nix
+$(d)/src/command-ref/conf-file.md: $(d)/conf-file.json $(d)/utils.nix $(d)/src/command-ref/conf-file-prefix.md $(bindir)/nix
 	@cat doc/manual/src/command-ref/conf-file-prefix.md > $@.tmp
-	$(trace-gen) $(nix-eval) --expr 'import doc/manual/generate-options.nix (builtins.fromJSON (builtins.readFile $<))' >> $@.tmp;
+	$(trace-gen) $(nix-eval) --expr '(import doc/manual/utils.nix).showSettings true (builtins.fromJSON (builtins.readFile $<))' >> $@.tmp;
 	@mv $@.tmp $@
 
 $(d)/nix.json: $(bindir)/nix
-	$(trace-gen) $(dummy-env) $(bindir)/nix __dump-args > $@.tmp
+	$(trace-gen) $(dummy-env) $(bindir)/nix __dump-cli > $@.tmp
 	@mv $@.tmp $@
 
 $(d)/conf-file.json: $(bindir)/nix

doc/manual/src/release-notes/rl-next.md

@@ -26,4 +26,6 @@
   ```shell-session
   $ nix path-info /nix/store/gzaflydcr6sb3567hap9q6srzx8ggdgg-glibc-2.33-78.drv^*
   ```
-  provides information about each of its outputs.
+  provides information about each of its outputs.
+
+* The command `nix describe-stores` has been removed.

doc/manual/utils.nix

@@ -38,4 +38,46 @@ rec {
 
   filterAttrs = pred: set:
     listToAttrs (concatMap (name: let v = set.${name}; in if pred name v then [(nameValuePair name v)] else []) (attrNames set));
+
+  showSetting = useSpans: name: { description, documentDefault, defaultValue, aliases, ... }:
+    let
+      result = squash ''
+          - ${if useSpans
+              then ''<span id="conf-${name}">[`${name}`](#conf-${name})</span>''
+              else ''[`${name}`](#conf-${name})''}
+
+          ${indent "  " body}
+        '';
+
+      # separate body to cleanly handle indentation
+      body = ''
+          ${description}
+
+          **Default:** ${showDefault documentDefault defaultValue}
+
+          ${showAliases aliases}
+        '';
+
+      showDefault = documentDefault: defaultValue:
+        if documentDefault then
+          # a StringMap value type is specified as a string, but
+          # this shows the value type. The empty stringmap is `null` in
+          # JSON, but that converts to `{ }` here.
+          if defaultValue == "" || defaultValue == [] || isAttrs defaultValue
+            then "*empty*"
+            else if isBool defaultValue then
+              if defaultValue then "`true`" else "`false`"
+            else "`${toString defaultValue}`"
+        else "*machine-specific*";
+
+      showAliases = aliases:
+          if aliases == [] then "" else
+            "**Deprecated alias:** ${(concatStringsSep ", " (map (s: "`${s}`") aliases))}";
+
+      indent = prefix: s:
+        concatStringsSep "\n" (map (x: if x == "" then x else "${prefix}${x}") (splitLines s));
+
+    in result;
+
+  showSettings = useSpans: settingsInfo: concatStrings (attrValues (mapAttrs (showSetting useSpans) settingsInfo));
 }

src/libcmd/command.hh

@@ -18,6 +18,7 @@ class EvalState;
 struct Pos;
 class Store;
 
+static constexpr Command::Category catHelp = -1;
 static constexpr Command::Category catSecondary = 100;
 static constexpr Command::Category catUtility = 101;
 static constexpr Command::Category catNixInstallation = 102;

src/libstore/dummy-store.cc

@@ -7,6 +7,13 @@ struct DummyStoreConfig : virtual StoreConfig {
     using StoreConfig::StoreConfig;
 
     const std::string name() override { return "Dummy Store"; }
+
+    std::string doc() override
+    {
+        return
+          #include "dummy-store.md"
+          ;
+    }
 };
 
 struct DummyStore : public virtual DummyStoreConfig, public virtual Store

src/libstore/dummy-store.md

@@ -0,0 +1,13 @@
+R"(
+
+**Store URL format**: `dummy://`
+
+This store type represents a store that contains no store paths and
+cannot be written to. It's useful when you want to use the Nix
+evaluator when no actual Nix store exists, e.g.
+
+```console
+# nix eval --store dummy:// --expr '1 + 2'
+```
+
+)"

src/libstore/globals.hh

@@ -97,7 +97,10 @@ public:
     Path nixDaemonSocketFile;
 
     Setting<std::string> storeUri{this, getEnv("NIX_REMOTE").value_or("auto"), "store",
-        "The default Nix store to use."};
+        R"(
+          The URL of the Nix store to use. See [`nix help-stores`](@docroot@/command-ref/new-cli/nix3-help-stores.md)
+          for supported store types and settings.
+        )"};
 
     Setting<bool> keepFailed{this, false, "keep-failed",
         "Whether to keep temporary directories of failed builds."};

src/libstore/http-binary-cache-store.cc

@@ -12,7 +12,14 @@ struct HttpBinaryCacheStoreConfig : virtual BinaryCacheStoreConfig
 {
     using BinaryCacheStoreConfig::BinaryCacheStoreConfig;
 
-    const std::string name() override { return "Http Binary Cache Store"; }
+    const std::string name() override { return "HTTP Binary Cache Store"; }
+
+    std::string doc() override
+    {
+        return
+          #include "http-binary-cache-store.md"
+          ;
+    }
 };
 
 class HttpBinaryCacheStore : public virtual HttpBinaryCacheStoreConfig, public virtual BinaryCacheStore

src/libstore/http-binary-cache-store.md

@@ -0,0 +1,8 @@
+R"(
+
+**Store URL format**: `http://...`, `https://...`
+
+This store allows a binary cache to be accessed via the HTTP
+protocol.
+
+)"

src/libstore/legacy-ssh-store.cc

@@ -22,7 +22,14 @@ struct LegacySSHStoreConfig : virtual StoreConfig
     const Setting<Path> remoteProgram{(StoreConfig*) this, "nix-store", "remote-program", "path to the nix-store executable on the remote system"};
     const Setting<std::string> remoteStore{(StoreConfig*) this, "", "remote-store", "URI of the store on the remote system"};
 
-    const std::string name() override { return "Legacy SSH Store"; }
+    const std::string name() override { return "SSH Store"; }
+
+    std::string doc() override
+    {
+        return
+          #include "legacy-ssh-store.md"
+          ;
+    }
 };
 
 struct LegacySSHStore : public virtual LegacySSHStoreConfig, public virtual Store

src/libstore/legacy-ssh-store.md

@@ -0,0 +1,8 @@
+R"(
+
+**Store URL format**: `ssh://[username@]hostname`
+
+This store type allows limited access to a remote store on another
+machine via SSH.
+
+)"

src/libstore/local-binary-cache-store.cc

@@ -11,6 +11,13 @@ struct LocalBinaryCacheStoreConfig : virtual BinaryCacheStoreConfig
     using BinaryCacheStoreConfig::BinaryCacheStoreConfig;
 
     const std::string name() override { return "Local Binary Cache Store"; }
+
+    std::string doc() override
+    {
+        return
+          #include "local-binary-cache-store.md"
+          ;
+    }
 };
 
 class LocalBinaryCacheStore : public virtual LocalBinaryCacheStoreConfig, public virtual BinaryCacheStore

src/libstore/local-binary-cache-store.md

@@ -0,0 +1,16 @@
+R"(
+
+**Store URL format**: `file://`*path*
+
+This store allows reading and writing a binary cache stored in *path*
+in the local filesystem. If *path* does not exist, it will be created.
+
+For example, the following builds or downloads `nixpkgs#hello` into
+the local store and then copies it to the binary cache in
+`/tmp/binary-cache`:
+
+```
+# nix copy --to file:///tmp/binary-cache nixpkgs#hello
+```
+
+)"

src/libstore/local-store.cc

@@ -44,6 +44,13 @@
 
 namespace nix {
 
+std::string LocalStoreConfig::doc()
+{
+    return
+        #include "local-store.md"
+        ;
+}
+
 struct LocalStore::State::Stmts {
     /* Some precompiled SQLite statements. */
     SQLiteStmt RegisterValidPath;

src/libstore/local-store.hh

@@ -41,8 +41,9 @@ struct LocalStoreConfig : virtual LocalFSStoreConfig
         "require-sigs", "whether store paths should have a trusted signature on import"};
 
     const std::string name() override { return "Local Store"; }
-};
 
+    std::string doc() override;
+};
 
 class LocalStore : public virtual LocalStoreConfig, public virtual LocalFSStore, public virtual GcStore
 {

src/libstore/local-store.md

@@ -0,0 +1,40 @@
+R"(
+
+**Store URL format**: `local`, *root*
+
+This store type accesses a Nix store in the local filesystem directly
+(i.e. not via the Nix daemon). *root* is an absolute path that denotes
+the "root" of the filesystem; other directories such as the Nix store
+directory (as denoted by the `store` setting) are interpreted relative
+to *root*. The store pseudo-URL `local` denotes a store that uses `/`
+as its root directory.
+
+A store that uses a *root* other than `/` is called a *chroot
+store*. With such stores, the store directory is "logically" still
+`/nix/store`, so programs stored in them can only be built and
+executed by `chroot`-ing into *root*. Chroot stores only support
+building and running on Linux when mount and user namespaces are
+enabled.
+
+For example, the following uses `/tmp/root` as the chroot environment
+to build or download `nixpkgs#hello` and then execute it:
+
+```console
+# nix run --store /tmp/root nixpkgs#hello
+Hello, world!
+```
+
+Here, the "physical" store location is `/tmp/root/nix/store`, and
+Nix's store metadata is in `/tmp/root/nix/var/nix/db`.
+
+It is also possible, but not recommended, to change the "logical"
+location of the Nix store from its default of `/nix/store`. This makes
+it impossible to use default substituters such as
+`https://cache.nixos.org/`, and thus you may have to build everything
+locally. Here is an example:
+
+```console
+# nix build --store 'local?store=/tmp/my-nix/store&state=/tmp/my-nix/state&log=/tmp/my-nix/log' nixpkgs#hello
+```
+
+)"

src/libstore/s3-binary-cache-store.cc

@@ -205,6 +205,13 @@ struct S3BinaryCacheStoreConfig : virtual BinaryCacheStoreConfig
         (StoreConfig*) this, 5 * 1024 * 1024, "buffer-size", "size (in bytes) of each part in multi-part uploads"};
 
     const std::string name() override { return "S3 Binary Cache Store"; }
+
+    std::string doc() override
+    {
+        return
+          #include "s3-binary-cache-store.md"
+          ;
+    }
 };
 
 struct S3BinaryCacheStoreImpl : virtual S3BinaryCacheStoreConfig, public virtual S3BinaryCacheStore

src/libstore/s3-binary-cache-store.md

@@ -0,0 +1,8 @@
+R"(
+
+**Store URL format**: `s3://`*bucket-name*
+
+This store allows reading and writing a binary cache stored in an AWS
+S3 bucket.
+
+)"