From 340aaf6a78421e90f06f8a30a0927d09d3471b58 Mon Sep 17 00:00:00 2001
From: Kitson Kelly <me@kitsonkelly.com>
Date: Wed, 1 Apr 2020 21:50:14 +1100
Subject: [PATCH] Support dynamic import in bundles.

Fixes #4062
---
 cli/tests/integration_tests.rs             | 32 ++++++++++++++++++++++
 cli/tests/subdir/subdir2/dynamic_import.ts |  6 ++++
 deno_typescript/README.md                  | 11 ++++++++
 deno_typescript/system_loader.js           | 21 +++++++++++++-
 4 files changed, 69 insertions(+), 1 deletion(-)
 create mode 100644 cli/tests/subdir/subdir2/dynamic_import.ts

diff --git a/cli/tests/integration_tests.rs b/cli/tests/integration_tests.rs
index 8342da10864316..98c564b4d9a051 100644
--- a/cli/tests/integration_tests.rs
+++ b/cli/tests/integration_tests.rs
@@ -490,6 +490,38 @@ fn bundle_js() {
   assert_eq!(output.stderr, b"");
 }
 
+#[test]
+fn bundle_dynamic_import() {
+  let dynamic_import =
+    util::root_path().join("cli/tests/subdir/subdir2/dynamic_import.ts");
+  assert!(dynamic_import.is_file());
+  let t = TempDir::new().expect("tempdir fail");
+  let bundle = t.path().join("dynamic_import.bundle.js");
+  let mut deno = util::deno_cmd()
+    .current_dir(util::root_path())
+    .arg("bundle")
+    .arg(dynamic_import)
+    .arg(&bundle)
+    .spawn()
+    .expect("failed to spawn script");
+  let status = deno.wait().expect("failed to wait for the child process");
+  assert!(status.success());
+  assert!(bundle.is_file());
+
+  let output = util::deno_cmd()
+    .current_dir(util::root_path())
+    .arg("run")
+    .arg(&bundle)
+    .output()
+    .expect("failed to spawn script");
+  // check the output of the test.ts program.
+  assert!(std::str::from_utf8(&output.stdout)
+    .unwrap()
+    .trim()
+    .ends_with("Hello"));
+  assert_eq!(output.stderr, b"");
+}
+
 #[test]
 fn repl_test_console_log() {
   let (out, err) = util::run_and_collect_output(
diff --git a/cli/tests/subdir/subdir2/dynamic_import.ts b/cli/tests/subdir/subdir2/dynamic_import.ts
new file mode 100644
index 00000000000000..3dccaca04b5502
--- /dev/null
+++ b/cli/tests/subdir/subdir2/dynamic_import.ts
@@ -0,0 +1,6 @@
+(async () => {
+  const { printHello } = await import("../print_hello.ts");
+  printHello();
+})();
+
+export {};
diff --git a/deno_typescript/README.md b/deno_typescript/README.md
index 220b04ae4d264a..8ab969c784f917 100644
--- a/deno_typescript/README.md
+++ b/deno_typescript/README.md
@@ -34,6 +34,17 @@ module specifier, a reference to the dynamic `import()` and the equivalent of
 and its value, or an object record of keys of the named exports and the values
 of the exports.
 
+Currently, TypeScript does not re-write dynamic imports which resolve to static
+strings (see
+[microsoft/TypeScript#37429](https://github.com/microsoft/TypeScript/issues/37429)),
+which means the import specifier for a dynamic import which has been
+incorporated in the bundle does not automatically match a module specifier that
+has been registered in the bundle. The `di()` function provides the capability
+to try to identify relative import specifiers and resolve them to a specifier
+inside the bundle. If it does this, it resolves with the exports of the module,
+otherwise it simply passes the module specifier to `import()` and returns the
+resulting promise.
+
 The running of the factories is handled by `rF()`. When the factory is run, it
 returns an object with two keys, `execute` and `setters`. `execute` is a
 function which finalises that instantiation of the module, and `setters` which
diff --git a/deno_typescript/system_loader.js b/deno_typescript/system_loader.js
index b5b10af480c55c..537d852b5ea4f2 100644
--- a/deno_typescript/system_loader.js
+++ b/deno_typescript/system_loader.js
@@ -15,10 +15,29 @@ let System, __instantiateAsync, __instantiate;
     },
   };
 
+  async function dI(mid, src) {
+    let id = mid.replace(/\.\w+$/i, "");
+    if (id.includes("./")) {
+      const [o, ...ia] = id.split("/").reverse(),
+        [, ...sa] = src.split("/").reverse(),
+        oa = [o];
+      let s = 0,
+        i;
+      while ((i = ia.shift())) {
+        if (i === "..") s++;
+        else if (i === ".") break;
+        else oa.push(i);
+      }
+      if (s < sa.length) oa.push(...sa.slice(s));
+      id = oa.reverse().join("/");
+    }
+    return r.has(id) ? r.get(id).exp : import(mid);
+  }
+
   function gC(id, main) {
     return {
       id,
-      import: async (id) => r.get(id)?.exp,
+      import: (m) => dI(m, id),
       meta: { url: id, main },
     };
   }