Support resolve hook

src/es-module-shims.js

@@ -91,7 +91,8 @@ async function importShim (id, parentUrl = pageBaseUrl, _assertion) {
   await featureDetectionPromise;
   // Make sure all the "in-flight" import maps are loaded and applied.
   await importMapPromise;
-  return topLevelLoad(resolve(id, parentUrl).r || throwUnresolved(id, parentUrl), { credentials: 'same-origin' });
+  const resolved = await resolve(id, parentUrl);
+  return topLevelLoad(resolved.r || throwUnresolved(id, parentUrl), { credentials: 'same-origin' });
 }
 
 self.importShim = importShim;
@@ -102,7 +103,8 @@ const edge = navigator.userAgent.match(/Edge\/\d\d\.\d+$/);
 
 async function importMetaResolve (id, parentUrl = this.url) {
   await importMapPromise;
-  return resolve(id, `${parentUrl}`).r || throwUnresolved(id, parentUrl);
+  const resolved = await resolve(id, `${parentUrl}`);
+  return resolved.r || throwUnresolved(id, parentUrl);
 }
 
 self._esmsm = meta;
@@ -142,7 +144,7 @@ function resolveDeps (load, seen) {
   const source = load.S;
 
   // edge doesnt execute sibling in order, so we fix this up by ensuring all previous executions are explicit dependencies
-  let resolvedSource = edge && lastLoad ? `import '${lastLoad}';` : '';  
+  let resolvedSource = edge && lastLoad ? `import '${lastLoad}';` : '';
 
   if (!imports.length) {
     resolvedSource += source;
@@ -279,13 +281,13 @@ function getOrCreateLoad (url, fetchOpts, source) {
 
   load.L = load.f.then(async () => {
     let childFetchOpts = fetchOpts;
-    load.d = await Promise.all(load.a[0].map(({ n, d, a }) => {
+    load.d = (await Promise.all(load.a[0].map(async ({ n, d, a }) => {
       if (d >= 0 && !supportsDynamicImport ||
           d === 2 && (!supportsImportMeta || source.slice(end, end + 8) === '.resolve') ||
           a && !supportsJsonAssertions)
         load.n = true;
       if (!n) return;
-      const { r, m } = resolve(n, load.r || load.u);
+      const { r, m } = await resolve(n, load.r || load.u);
       if (m && (!supportsImportMaps || importMapSrcOrLazy))
         load.n = true;
       if (d !== -1) return;
@@ -295,7 +297,7 @@ function getOrCreateLoad (url, fetchOpts, source) {
       if (childFetchOpts.integrity)
         childFetchOpts = Object.assign({}, childFetchOpts, { integrity: undefined });
       return getOrCreateLoad(r, childFetchOpts).f;
-    }).filter(l => l));
+    }))).filter(l => l);
   });
 
   return load;
@@ -386,14 +388,26 @@ function processPreload (link) {
   link.ep = true;
   // prepopulate the load record
   const fetchOpts = getFetchOpts(link);
-  // save preloaded fetch options for later load  
+  // save preloaded fetch options for later load
   fetchOptsMap.set(link.href, fetchOpts);
   fetch(link.href, fetchOpts);
 }
 
-function resolve (id, parentUrl) {
-  const urlResolved = resolveIfNotPlainOrUrl(id, parentUrl);
-  const resolved = resolveImportMap(importMap, urlResolved || id, parentUrl);
+function defaultResolve(id, parentUrl) {
+  return resolveImportMap(importMap, resolveIfNotPlainOrUrl(id, parentUrl) || id, parentUrl);
+}
+
+async function resolve(id, parentUrl) {
+  let urlResolved = resolveIfNotPlainOrUrl(id, parentUrl);
+
+  let resolved;
+  if (esmsInitOptions.resolve) {
+    resolved = await esmsInitOptions.resolve(id, parentUrl, defaultResolve);
+  }
+  else {
+    resolved = resolveImportMap(importMap, urlResolved || id, parentUrl);
+  }
+
   return { r: resolved, m: urlResolved !== resolved };
 }
 

test/resolve-hook.js

@@ -0,0 +1,18 @@
+
+suite('Resolve hook', () => {
+  test('Should hook resolve', async function () {
+    globalThis.esmsInitOptions = {
+      resolve: async function (id, parentUrl, defaultResolve) {
+        if (id === 'resolveTestModule') {
+          return defaultResolve('./fixtures/es-modules/es6.js', parentUrl);
+          // OR just resolve by yourself like this:
+          // return new URL('./fixtures/es-modules/es6.js', location.href).href;
+        }
+      }
+    };
+
+    await import('../src/es-module-shims.js');
+    var m = await importShim('resolveTestModule');
+    assert(m.p);
+  });
+});

test/test-resolve-hook.html

@@ -0,0 +1,48 @@
+<!doctype html>
+<link rel="stylesheet" type="text/css" href="../node_modules/mocha/mocha.css"/>
+<script src="../node_modules/mocha/mocha.js"></script>
+<script type="importmap-shim">
+  {
+    "imports": {
+      "test": "/test/fixtures/es-modules/es6-file.js"
+    }
+  }
+</script>
+<script type="module-shim">
+  import test from "test";
+  console.log(test);
+</script>
+<script type="module">
+  mocha.setup('tdd');
+  mocha.allowUncaught();
+
+  self.baseURL = location.href.substr(0, location.href.lastIndexOf('/') + 1);
+  self.rootURL = location.href.substr(0, location.href.length - 'test/test.html'.length);
+  self.assert = function (val) {
+    equal(!!val, true);
+  };
+  assert.equal = equal;
+  assert.ok = assert;
+  function equal (a, b) {
+    if (a !== b)
+      throw new Error('Expected "' + a + '" to be "' + b + '"');
+  }
+  self.fail = function (msg) {
+    throw new Error(msg);
+  };
+
+  const suites = ['resolve-hook'];
+  function runNextSuite () {
+    mocha.suite.suites = [];
+    const suite = suites.shift();
+    if (suite)
+      import('./' + suite + '.js')
+      .then(function () {
+        mocha.run(runNextSuite);
+      });
+  }
+
+  runNextSuite();
+</script>
+
+<div id="mocha"></div>