fix: support ts passthrough for no typestripping (#459)

chompfile.toml

@@ -44,7 +44,10 @@ ${amaroSource}
 const amaroTransformSync = module.exports.transformSync;
 export function transform(source, url) {
   try {
-    return amaroTransformSync(source, { filename: url, transform: { mode: 'strip-only', noEmptyExport: true } }).code;
+    const transformed = amaroTransformSync(source, { filename: url, transform: { mode: 'strip-only', noEmptyExport: true } }).code;
+    // Importantly, return undefined when there is no work to do
+    if (transformed !== source)
+      return transformed;
   } catch (e) {
     // This is needed pending figuring out why filename option above isn't working
     throw new SyntaxError(e.message.replace(',-', url + ' - '));

src/es-module-shims.js

@@ -576,7 +576,7 @@ async function fetchModule(url, fetchOpts, parent) {
     const source = await res.text();
     if (!esmsTsTransform) await initTs();
     const transformed = esmsTsTransform(source, url);
-    return { r, s: transformed || source, t: transformed ? 'ts' : 'js' };
+    return { r, s: transformed === undefined ? source : transformed, t: transformed !== undefined ? 'ts' : 'js' };
   } else
     throw Error(
       `Unsupported Content-Type "${contentType}" loading ${url}${fromParent(parent)}. Modules must be served with a valid MIME type like application/javascript.`
@@ -796,15 +796,16 @@ function processScript(script, ready = readyStateCompleteCnt > 0) {
   if (script.lang === 'ts' && !script.src) {
     const source = script.innerHTML;
     return initTs()
-      .then(() =>
-        topLevelLoad(
+      .then(() => {
+        const transformed = esmsTsTransform(source, pageBaseUrl);
+        return topLevelLoad(
           pageBaseUrl,
           getFetchOpts(script),
-          esmsTsTransform(source, pageBaseUrl) || source,
-          undefined,
+          transformed === undefined ? source : transformed,
+          transformed === undefined,
           undefined
-        )
-      )
+        );
+      })
       .catch(throwError);
   }
   if (self.ESMS_DEBUG) console.info(`es-module-shims: checking script ${script.src || '<inline>'}`);

test/test-ts.html

@@ -32,4 +32,9 @@
   window.inlineTypescript as test = true;
 </script>
 
+<script type="module" lang="ts">
+  window.inlineTypescriptNoWork = window.inlineTypescriptNoWork || 0;
+  window.inlineTypescriptNoWork++;
+</script>
+
 <div id="mocha"></div>

test/typescript.js

@@ -1,11 +1,17 @@
 suite('TypeScript loading tests', () => {
+  const timeoutInitPromise = new Promise(resolve => setTimeout(resolve, 1000));
   test('Inline lang=ts support', async function () {
-    await new Promise(resolve => setTimeout(resolve, 1000));
+    await timeoutInitPromise;
+    assert.ok(globalThis.inlineTypescriptNoWork === 1);
+  });
+
+  test('Inline lang=ts support for no work', async function () {
+    await timeoutInitPromise;
     assert.ok(globalThis.inlineTypescript === true);
   });
 
   test('Static TS script', async function () {
-    await new Promise(resolve => setTimeout(resolve, 1000));
+    await timeoutInitPromise;
     assert.ok(globalThis.executedTs === true);
   });