PostCSS: Improve error recovery

CHANGELOG.md

@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Hide default shadow suggestions when missing theme keys ([#17743](https://github.com/tailwindlabs/tailwindcss/pull/17743))
 - Replace `_` with `.` in theme suggestions for `@utility` if surrounded by digits ([#17743](https://github.com/tailwindlabs/tailwindcss/pull/17743))
 - Upgrade: Bump all Tailwind CSS related dependencies during upgrade ([#17763](https://github.com/tailwindlabs/tailwindcss/pull/17763))
+- PostCSS: Ensure that errors in stylesheet dependencies are recoverable ([#17754](https://github.com/tailwindlabs/tailwindcss/pull/17754))
 
 ## [4.1.4] - 2025-04-14
 

integrations/postcss/index.test.ts

@@ -635,3 +635,91 @@ test(
     await fs.expectFileToContain('project-a/dist/out.css', [candidate`content-['c/src/index.js']`])
   },
 )
+
+test(
+  'rebuild error recovery',
+  {
+    fs: {
+      'package.json': json`
+        {
+          "devDependencies": {
+            "postcss": "^8",
+            "postcss-cli": "^10",
+            "tailwindcss": "workspace:^",
+            "@tailwindcss/postcss": "workspace:^"
+          }
+        }
+      `,
+      'postcss.config.js': js`
+        module.exports = {
+          plugins: {
+            '@tailwindcss/postcss': {},
+          },
+        }
+      `,
+      'src/index.html': html`
+        <div class="underline"></div>
+      `,
+      'src/index.css': css` @import './tailwind.css'; `,
+      'src/tailwind.css': css`
+        @reference 'tailwindcss/does-not-exist';
+        @import 'tailwindcss/utilities';
+      `,
+    },
+  },
+  async ({ fs, expect, spawn }) => {
+    let process = await spawn('pnpm postcss src/index.css --output dist/out.css --watch --verbose')
+
+    await process.onStderr((message) =>
+      message.includes('Package path ./does-not-exist is not exported from package'),
+    )
+
+    expect(await fs.dumpFiles('dist/*.css')).toMatchInlineSnapshot(`
+      "
+      --- dist/out.css ---
+      <EMPTY>
+      "
+    `)
+
+    await process.onStderr((message) => message.includes('Waiting for file changes...'))
+
+    // Fix the CSS file
+    await fs.write(
+      'src/tailwind.css',
+      css`
+        @reference 'tailwindcss/theme';
+        @import 'tailwindcss/utilities';
+      `,
+    )
+    await process.onStderr((message) => message.includes('Finished src/index.css'))
+
+    expect(await fs.dumpFiles('dist/*.css')).toMatchInlineSnapshot(`
+      "
+      --- dist/out.css ---
+      .underline {
+        text-decoration-line: underline;
+      }
+      "
+    `)
+
+    // Now break the CSS file again
+    await fs.write(
+      'src/tailwind.css',
+      css`
+        @reference 'tailwindcss/does-not-exist';
+        @import 'tailwindcss/utilities';
+      `,
+    )
+    await process.onStderr((message) =>
+      message.includes('Package path ./does-not-exist is not exported from package'),
+    )
+    await process.onStderr((message) => message.includes('Finished src/index.css'))
+
+    expect(await fs.dumpFiles('dist/*.css')).toMatchInlineSnapshot(`
+      "
+      --- dist/out.css ---
+      <EMPTY>
+      "
+    `)
+  },
+)