Handle script module resolution (#438)

Fixes #104

7 files changed, 68 insertions, 3 deletions

diff --git a/.changeset/kind-baboons-melt.md b/.changeset/kind-baboons-melt.md
new file mode 100644
index 000000000..018148358
--- /dev/null
+++ b/.changeset/kind-baboons-melt.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fix <script type="module"> resolution
diff --git a/packages/astro/src/build.ts b/packages/astro/src/build.ts
index ef26c5a5c..1f11a6acf 100644
--- a/packages/astro/src/build.ts
+++ b/packages/astro/src/build.ts
@@ -110,6 +110,9 @@ export async function build(astroConfig: AstroConfig, logging: LogOptions = defa
           scanPromises.push(
             runtime.load(url).then((result) => {
               if (result.statusCode !== 200) {
+                if (result.statusCode === 404) {
+                  throw new Error(`${buildState[id].srcPath.href}: could not find "${path.basename(url)}"`);
+                }
                 // there shouldn’t be a build error here
                 throw (result as any).error || new Error(`unexpected status ${result.statusCode} when loading ${url}`);
               }
diff --git a/packages/astro/src/compiler/transform/module-scripts.ts b/packages/astro/src/compiler/transform/module-scripts.ts
index 46defb1bd..98385b105 100644
--- a/packages/astro/src/compiler/transform/module-scripts.ts
+++ b/packages/astro/src/compiler/transform/module-scripts.ts
@@ -24,8 +24,23 @@ export default function ({ compileOptions, filename }: { compileOptions: Compile
             }
 
             let src = getAttrValue(node.attributes, 'src');
-            if (!src || !src.startsWith('.')) {
+
+            // scenario 1: if missing "src", ignore
+            if (!src) {
+              return;
+            }
+
+            // scenario 2: if absolute path, ignore
+            if (src.startsWith('/')) {
+              return;
+            }
+
+            // scenario 3: if remote URL, ignore
+            try {
+              new URL(src); // if this succeeds, this is a complete, valid URL
               return;
+            } catch (err) {
+              // do nothing
             }
 
             const srcUrl = new URL(src, fileUrl);
diff --git a/packages/astro/test/astro-resolve.test.js b/packages/astro/test/astro-resolve.test.js
index ea9a307e6..d98573120 100644
--- a/packages/astro/test/astro-resolve.test.js
+++ b/packages/astro/test/astro-resolve.test.js
@@ -1,5 +1,6 @@
 import { suite } from 'uvu';
 import * as assert from 'uvu/assert';
+import { doc } from './test-utils.js';
 import { setupBuild } from './helpers.js';
 
 const Resolution = suite('Astro Resolution');
@@ -9,11 +10,30 @@ setupBuild(Resolution, './fixtures/astro-resolve');
 Resolution('Assets', async (context) => {
   await context.build();
 
-  // public/ asset resolved
+  // test 1: public/ asset resolved
   assert.ok(await context.readFile('/svg.svg'));
 
-  // asset in src/pages resolved (and didn’t overwrite /svg.svg)
+  // test 2: asset in src/pages resolved (and didn’t overwrite /svg.svg)
   assert.ok(await context.readFile('/_astro/src/pages/svg.svg'));
 });
 
+Resolution('<script type="module">', async (context) => {
+  await context.build();
+
+  // public/ asset resolved
+  const $ = doc(await context.readFile('/scripts/index.html'));
+
+  // test 1: not `type="module"` left alone
+  assert.equal($('script[src="./relative.js"]').attr('type'), undefined);
+
+  // test 2: inline script left alone
+  assert.equal($('script:not([type]):not([src])').length, 1);
+
+  // test 3: relative script resolved
+  assert.equal($('script[type="module"][src="/_astro/src/pages/relative.js"]').length, 2); // we have 2 of these!
+
+  // test 4: absolute script left alone
+  assert.equal($('script[type="module"][src="/absolute.js"]').length, 1);
+});
+
 Resolution.run();
diff --git a/packages/astro/test/fixtures/astro-resolve/public/absolute.js b/packages/astro/test/fixtures/astro-resolve/public/absolute.js
new file mode 100644
index 000000000..9892d29e5
--- /dev/null
+++ b/packages/astro/test/fixtures/astro-resolve/public/absolute.js
@@ -0,0 +1 @@
+console.log('I’m absolute');
diff --git a/packages/astro/test/fixtures/astro-resolve/src/pages/relative.js b/packages/astro/test/fixtures/astro-resolve/src/pages/relative.js
new file mode 100644
index 000000000..c264d183c
--- /dev/null
+++ b/packages/astro/test/fixtures/astro-resolve/src/pages/relative.js
@@ -0,0 +1 @@
+console.log('I’m relative');
diff --git a/packages/astro/test/fixtures/astro-resolve/src/pages/scripts.astro b/packages/astro/test/fixtures/astro-resolve/src/pages/scripts.astro
new file mode 100644
index 000000000..603fe6b91
--- /dev/null
+++ b/packages/astro/test/fixtures/astro-resolve/src/pages/scripts.astro
@@ -0,0 +1,20 @@
+<html>
+  <head></head>
+
+  <body>
+    <!-- not `type="module"` -->
+    <script src="./relative.js"></script>
+
+    <!-- no `src` -->
+    <script></script>
+
+    <!-- type="module" with NO "./" -->
+    <script type="module" src="relative.js"></script>
+
+    <!-- type="module" WITH leading "./" -->
+    <script type="module" src="./relative.js"></script>
+
+    <!-- absolute URL -->
+    <script type="module" src="/absolute.js"></script>
+  </body>
+</html>