PostCSS: Fix Turbopack 'one-revision-behind' bug

CHANGELOG.md

@@ -7,7 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-- Nothing yet!
+### Fixed
+
+- PostCSS: Resolve an issue where changes to the input CSS file showed outdated content when using Turbopack ([#17554](https://github.com/tailwindlabs/tailwindcss/pull/17554))
 
 ## [4.1.2] - 2025-04-03
 

packages/@tailwindcss-postcss/src/fixtures/example-project/input.css

@@ -0,0 +1 @@
+/* the content for this file is set in the tests */

packages/@tailwindcss-postcss/src/index.test.ts

@@ -420,3 +420,25 @@ describe('concurrent builds', () => {
     expect(await promise2).toContain('.red')
   })
 })
+
+test('does not register the input file as a dependency, even if it is passed in as relative path', async () => {
+  let processor = postcss([
+    tailwindcss({ base: `${__dirname}/fixtures/example-project`, optimize: { minify: false } }),
+  ])
+
+  let result = await processor.process(`@tailwind utilities`, { from: './input.css' })
+
+  expect(result.css.trim()).toMatchInlineSnapshot(`
+    ".underline {
+      text-decoration-line: underline;
+    }"
+  `)
+
+  // Check for dependency messages
+  expect(result.messages).not.toContainEqual({
+    type: 'dependency',
+    file: expect.stringMatching(/input.css$/g),
+    parent: expect.any(String),
+    plugin: expect.any(String),
+  })
+})

packages/@tailwindcss-postcss/src/index.ts

@@ -223,10 +223,12 @@ function tailwindcss(opts: PluginOptions = {}): AcceptedPlugin {
           if (compiler.features & Features.Utilities) {
             DEBUG && I.start('Register dependency messages')
             // Add all found files as direct dependencies
+            // Note: With Turbopack, the input file might not be a resolved path
+            let resolvedInputFile = path.resolve(base, inputFile)
             for (let file of context.scanner.files) {
               let absolutePath = path.resolve(file)
               // The CSS file cannot be a dependency of itself
-              if (absolutePath === result.opts.from) {
+              if (absolutePath === resolvedInputFile) {
                 continue
               }
               result.messages.push({