feat: import.meta.resolve() (#15074)

This commit adds new "import.meta.resolve()" API which
allows to resolve specifiers relative to the module the API
is called in. This API supports resolving using import maps.

cli/dts/lib.deno.ns.d.ts

@@ -21,6 +21,16 @@ declare interface ImportMeta {
    * ```
    */
   main: boolean;
+
+  /** A function that returns resolved specifier as if it would be imported
+   * using `import(specifier)`.
+   *
+   * ```ts
+   * console.log(import.meta.resolve("./foo.js"));
+   * // file:///dev/foo.js
+   * ```
+   */
+  resolve(specifier: string): string;
 }
 
 /** Deno supports user timing Level 3 (see: https://w3c.github.io/user-timing)

cli/tests/integration/run_tests.rs

@@ -952,7 +952,7 @@ itest!(if_main {
 });
 
 itest!(import_meta {
-  args: "run --quiet --reload import_meta.ts",
+  args: "run --quiet --reload --import-map=import_meta.importmap.json import_meta.ts",
   output: "import_meta.ts.out",
 });
 

cli/tests/testdata/import_meta.importmap.json

@@ -0,0 +1,11 @@
+{
+  "imports": {
+    "bare": "https://example.com/",
+    "https://example.com/rewrite": "https://example.com/rewritten",
+
+    "1": "https://example.com/PASS-1",
+    "null": "https://example.com/PASS-null",
+    "undefined": "https://example.com/PASS-undefined",
+    "[object Object]": "https://example.com/PASS-object"
+  }
+}

cli/tests/testdata/import_meta.ts

@@ -1,3 +1,34 @@
+import { assertThrows } from "../../../test_util/std/testing/asserts.ts";
+
 console.log("import_meta", import.meta.url, import.meta.main);
 
 import "./import_meta2.ts";
+
+console.log("Resolving ./foo.js", import.meta.resolve("./foo.js"));
+console.log("Resolving bare from import map", import.meta.resolve("bare"));
+console.log(
+  "Resolving https://example.com/rewrite from import map",
+  import.meta.resolve("https://example.com/rewrite"),
+);
+console.log(
+  "Resolving without a value from import map",
+  import.meta.resolve(),
+);
+console.log(
+  "Resolving 1 from import map",
+  import.meta.resolve(1),
+);
+console.log(
+  "Resolving null from import map",
+  import.meta.resolve(null),
+);
+console.log(
+  "Resolving object from import map",
+  import.meta.resolve({}),
+);
+assertThrows(() => {
+  import.meta.resolve("too", "many", "arguments");
+}, TypeError);
+assertThrows(() => {
+  import.meta.resolve("://malformed/url?asdf");
+}, TypeError);

cli/tests/testdata/import_meta.ts.out

@@ -1,2 +1,9 @@
 import_meta2 [WILDCARD]import_meta2.ts false
 import_meta [WILDCARD]import_meta.ts true
+Resolving ./foo.js file:///[WILDCARD]/foo.js
+Resolving bare from import map https://example.com/
+Resolving https://example.com/rewrite from import map https://example.com/rewritten
+Resolving without a value from import map https://example.com/PASS-undefined
+Resolving 1 from import map https://example.com/PASS-1
+Resolving null from import map https://example.com/PASS-null
+Resolving object from import map https://example.com/PASS-object

core/bindings.rs

@@ -271,6 +271,47 @@ pub extern "C" fn host_initialize_import_meta_object_callback(
   let main_key = v8::String::new(scope, "main").unwrap();
   let main_val = v8::Boolean::new(scope, info.main);
   meta.create_data_property(scope, main_key.into(), main_val.into());
+
+  let builder =
+    v8::FunctionBuilder::new(import_meta_resolve).data(url_val.into());
+  let val = v8::FunctionBuilder::<v8::Function>::build(builder, scope).unwrap();
+  let resolve_key = v8::String::new(scope, "resolve").unwrap();
+  meta.set(scope, resolve_key.into(), val.into());
+}
+
+fn import_meta_resolve(
+  scope: &mut v8::HandleScope,
+  args: v8::FunctionCallbackArguments,
+  mut rv: v8::ReturnValue,
+) {
+  if args.length() > 1 {
+    return throw_type_error(scope, "Invalid arguments");
+  }
+
+  let maybe_arg_str = args.get(0).to_string(scope);
+  if maybe_arg_str.is_none() {
+    return throw_type_error(scope, "Invalid arguments");
+  }
+  let specifier = maybe_arg_str.unwrap();
+  let referrer = {
+    let url_prop = args.data().unwrap();
+    url_prop.to_rust_string_lossy(scope)
+  };
+  let module_map_rc = JsRuntime::module_map(scope);
+  let loader = {
+    let module_map = module_map_rc.borrow();
+    module_map.loader.clone()
+  };
+  match loader.resolve(&specifier.to_rust_string_lossy(scope), &referrer, false)
+  {
+    Ok(resolved) => {
+      let resolved_val = serde_v8::to_v8(scope, resolved.as_str()).unwrap();
+      rv.set(resolved_val);
+    }
+    Err(err) => {
+      throw_type_error(scope, &err.to_string());
+    }
+  };
 }
 
 pub extern "C" fn promise_reject_callback(message: v8::PromiseRejectMessage) {