From af3b2595f219dcb463f8804420ed9500193f1a24 Mon Sep 17 00:00:00 2001
From: John Gozde <john@gozde.ca>
Date: Sun, 9 Jul 2023 11:00:08 -0600
Subject: [PATCH] Rewrite asset paths if they reference actual esbuild outputs

---
 .changeset/honest-lions-breathe.md            |  5 +
 .../src/html-entry-point/write-template.ts    | 94 ++++++++++---------
 .../esbd-build-html.test.ts.snap              | 48 ++++++++++
 packages/esbd/test/esbd-build-html.test.ts    | 32 +++++++
 4 files changed, 133 insertions(+), 46 deletions(-)
 create mode 100644 .changeset/honest-lions-breathe.md

diff --git a/.changeset/honest-lions-breathe.md b/.changeset/honest-lions-breathe.md
new file mode 100644
index 0000000..6ff51fa
--- /dev/null
+++ b/.changeset/honest-lions-breathe.md
@@ -0,0 +1,5 @@
+---
+'esbd': minor
+---
+
+Rewrite asset paths if they reference actual esbuild outputs
diff --git a/packages/esbd/src/html-entry-point/write-template.ts b/packages/esbd/src/html-entry-point/write-template.ts
index b516636..75ad394 100644
--- a/packages/esbd/src/html-entry-point/write-template.ts
+++ b/packages/esbd/src/html-entry-point/write-template.ts
@@ -34,8 +34,8 @@ export interface WriteTemplateOptions extends EsbuildHtmlOptions {
 }
 
 interface FileSystem {
-  copyFile: typeof fsp['copyFile'];
-  writeFile: typeof fsp['writeFile'];
+  copyFile: (typeof fsp)['copyFile'];
+  writeFile: (typeof fsp)['writeFile'];
 }
 
 export async function writeTemplate(
@@ -64,7 +64,6 @@ export async function writeTemplate(
   }
 
   const copyFile = cachedCopyFile(fs.copyFile);
-  const outputCache = new Set<string>();
 
   const { document, head, body } = template;
 
@@ -73,7 +72,10 @@ export async function writeTemplate(
   const templateOutputPath = path.resolve(absOutDir, template.outputPath);
   const needsModuleType = format === 'esm';
 
-  const outputs: [entryPoint: string, outputPath: string][] = Object.keys(metafile.outputs)
+  const outputFilenames = Object.keys(metafile.outputs);
+
+  // Find emitted entry points and convert them to absolute paths
+  const entryOutputs: [entryPoint: string, outputPath: string][] = outputFilenames
     .map(o => [metafile.outputs[o], o] as const)
     .filter(([output]) => !!output.entryPoint)
     .map(([output, outputPath]) => [
@@ -81,32 +83,27 @@ export async function writeTemplate(
       path.relative(absTemplateDir, path.resolve(basedir, outputPath)),
     ]);
 
-  const cssOutput = new Map(outputs.filter(([, o]) => o.endsWith('.css')));
-  const jsOutput = new Map(outputs.filter(([, o]) => o.endsWith('.js')));
-
-  // Check whether any of the output file names have changed since the last
-  // build finished
-  let modified = false;
-  const currentOutputs = new Set([
-    ...Array.from(cssOutput.values()),
-    ...Array.from(jsOutput.values()),
-  ]);
-  for (const output of currentOutputs) {
-    if (!outputCache.has(output)) {
-      outputCache.add(output);
-      modified = true;
-    }
-  }
-  for (const output of outputCache) {
-    if (!currentOutputs.has(output)) {
-      outputCache.delete(output);
-      modified = true;
-    }
-  }
-
-  // If no output filenames have changed, then there is no need to emit
-  // the HTML
-  if (!modified) return;
+  // Find any output files that were produced from inputs with matching "href"
+  // attributes in any <link> or <style> tags. If any are found, this indicates
+  // that the files were referenced elsewhere in the dependency graph and esbuild
+  // has copied them to the output directory, possibly with a different basename.
+  // But if they _also_ appear in the HTML template, it might be for preloading/
+  // prefetching purposes. In that case, we don't want to copy them again; rather,
+  // we want to use the output path that esbuild has already produced.
+  const tagOutputs = tagAssets.map(([element, url]) => {
+    const matchingOutput = outputFilenames.find(o => {
+      const inputs = Object.keys(metafile.outputs[o].inputs);
+      if (inputs.length !== 1) return false;
+
+      const absInputPath = path.resolve(basedir, inputs[0]);
+      const absHrefPath = path.resolve(absTemplateDir, url);
+      return absInputPath === absHrefPath;
+    });
+    return [element, url, matchingOutput] as const;
+  });
+
+  const cssOutput = new Map(entryOutputs.filter(([, o]) => o.endsWith('.css')));
+  const jsOutput = new Map(entryOutputs.filter(([, o]) => o.endsWith('.js')));
 
   const htmlEntryPathsAbs = Object.values(htmlEntryPoints).map(filePath =>
     path.resolve(basedir, filePath),
@@ -251,27 +248,32 @@ export async function writeTemplate(
   // Rebase collected asset paths for tag assets (from <link> tags) and
   // text assets (from <style> tags)
   const assetPaths: [string, string][] = [];
-  for (const [node, url] of tagAssets) {
+  for (const [node, url, outputPath] of tagOutputs) {
+    const href = node.attrs.find(a => a.name === 'href');
+    if (!href) continue;
+
     const { basename, inputPath, rebasedURL } = rebaseAssetURL(
-      substituteDefines(url, define),
+      outputPath ?? substituteDefines(url, define),
       template.inputPath,
       publicPath,
     );
-    const href = node.attrs.find(a => a.name === 'href');
-    if (href) {
-      href.value = rebasedURL;
 
-      if (inputPath && basename) {
-        // TODO: parallelize this?
-        if (integrity) {
-          node.attrs.push({
-            name: 'integrity',
-            value: await calculateFileIntegrityHash(
-              path.resolve(absTemplateDir, inputPath),
-              integrity,
-            ),
-          });
-        }
+    href.value = rebasedURL;
+
+    if (inputPath && basename) {
+      // TODO: parallelize this?
+      if (integrity) {
+        node.attrs.push({
+          name: 'integrity',
+          value: await calculateFileIntegrityHash(
+            path.resolve(absTemplateDir, inputPath),
+            integrity,
+          ),
+        });
+      }
+      // If outputPath is defined, this file was already copied to the output directory
+      // by esbuild, so we don't need to copy it again.
+      if (!outputPath) {
         assetPaths.push([inputPath, path.resolve(absOutDir, basename)]);
       }
     }
diff --git a/packages/esbd/test/__snapshots__/esbd-build-html.test.ts.snap b/packages/esbd/test/__snapshots__/esbd-build-html.test.ts.snap
index 8b33bac..8470aa9 100644
--- a/packages/esbd/test/__snapshots__/esbd-build-html.test.ts.snap
+++ b/packages/esbd/test/__snapshots__/esbd-build-html.test.ts.snap
@@ -403,6 +403,54 @@ index.html
 
 `;
 
+exports[`build command (html entry) > includes referenced assets from HTML using their esbuild-generated output paths 1`] = `
+---------------------------------
+STDOUT
+---------------------------------
+✔  Finished index.html with 0 error(s) and 0 warning(s) in XX time
+---------------------------------
+entry.js
+---------------------------------
+// src/entry.tsx
+import ReactDOM from "react-dom";
+
+// assets/icon.svg
+var icon_default = "./icon-IPILGNO5.svg";
+
+// src/entry.tsx
+function App() {
+  return /* @__PURE__ */ React.createElement(
+    "div",
+    null,
+    "Hello world ",
+    /* @__PURE__ */ React.createElement("img", { src: icon_default })
+  );
+}
+ReactDOM.render(
+  /* @__PURE__ */ React.createElement(App, null),
+  document.getElementById("root")
+);
+
+---------------------------------
+icon-IPILGNO5.svg
+---------------------------------
+<svg></svg>
+---------------------------------
+index.html
+---------------------------------
+<!DOCTYPE html>
+<html>
+  <head>
+    <link rel="apple-touch-icon" href="icon-IPILGNO5.svg" />
+    <script defer="" type="module" src="entry.js"></script>
+  </head>
+  <body>
+    <div id="root"></div>
+  </body>
+</html>
+
+`;
+
 exports[`build command (html entry) > includes referenced assets from style tags 1`] = `
 ---------------------------------
 STDOUT
diff --git a/packages/esbd/test/esbd-build-html.test.ts b/packages/esbd/test/esbd-build-html.test.ts
index db12749..6e1fc5f 100644
--- a/packages/esbd/test/esbd-build-html.test.ts
+++ b/packages/esbd/test/esbd-build-html.test.ts
@@ -617,4 +617,36 @@ describe('build command (html entry)', () => {
       }),
     ).resolves.toMatchSnapshot();
   });
+
+  it('includes referenced assets from HTML using their esbuild-generated output paths', () => {
+    return expect(
+      buildWithHTML({
+        config: {
+          external: ['react', 'react-dom'],
+          loader: {
+            '.svg': 'file',
+          },
+        },
+        files: {
+          'index.html': `
+            <!DOCTYPE html>
+            <html>
+              <head>
+                <link rel="apple-touch-icon" href="./assets/icon.svg"/>
+                <script defer type="module" src="./src/entry.tsx"></script>
+              </head>
+              <body><div id='root'></div></body>
+            </html>
+          `,
+          'assets/icon.svg': '<svg></svg>',
+          'src/entry.tsx': `
+            import ReactDOM from 'react-dom';
+            import icon from '../assets/icon.svg';
+            function App() { return <div>Hello world <img src={icon} /></div>; }
+            ReactDOM.render(<App />, document.getElementById('root'));
+          `,
+        },
+      }),
+    ).resolves.toMatchSnapshot();
+  });
 });