Detect conflicting imports for potential utility files

Co-authored-by: Robin Malfait <[email protected]>

integrations/upgrade/index.test.ts

@@ -808,3 +808,68 @@ test(
     `)
   },
 )
+
+test(
+  'migrate utility files imported by multiple roots',
+  {
+    fs: {
+      'package.json': json`
+        {
+          "dependencies": {
+            "tailwindcss": "workspace:^",
+            "@tailwindcss/cli": "workspace:^",
+            "@tailwindcss/upgrade": "workspace:^"
+          }
+        }
+      `,
+      'tailwind.config.js': js`module.exports = {}`,
+      'src/index.html': html`
+        <div class="hover:thing"></div>
+      `,
+      'src/root.1.css': css`
+        @import 'tailwindcss/utilities';
+        @import './a.1.css' layer(utilities);
+      `,
+      'src/root.2.css': css`
+        @import 'tailwindcss/utilities';
+        @import './a.1.css' layer(components);
+      `,
+      'src/root.3.css': css`
+        @import 'tailwindcss/utilities';
+        @import './a.1.css';
+      `,
+      'src/a.1.css': css`
+        .foo-from-a {
+          color: red;
+        }
+      `,
+    },
+  },
+  async ({ fs, exec }) => {
+    let output = await exec('npx @tailwindcss/upgrade --force')
+
+    expect(output).toMatch(
+      /You have one or more stylesheets that are imported into a utility layer and non-utility layer./,
+    )
+
+    expect(await fs.dumpFiles('./src/**/*.css')).toMatchInlineSnapshot(`
+      "
+      --- ./src/a.1.css ---
+      .foo-from-a {
+        color: red;
+      }
+
+      --- ./src/root.1.css ---
+      @import 'tailwindcss/utilities' layer(utilities);
+      @import './a.1.css' layer(utilities);
+
+      --- ./src/root.2.css ---
+      @import 'tailwindcss/utilities' layer(utilities);
+      @import './a.1.css' layer(components);
+
+      --- ./src/root.3.css ---
+      @import 'tailwindcss/utilities' layer(utilities);
+      @import './a.1.css' layer(utilities);"
+    `)
+  },
+)

integrations/utils.ts

@@ -114,7 +114,7 @@ export function test(
                   if (execOptions.ignoreStdErr !== true) console.error(stderr)
                   reject(error)
                 } else {
-                  resolve(stdout.toString())
+                  resolve(stdout.toString() + '\n\n' + stderr.toString())
                 }
               },
             )

packages/@tailwindcss-upgrade/src/migrate.ts

@@ -9,7 +9,7 @@ import { migrateAtLayerUtilities } from './codemods/migrate-at-layer-utilities'
 import { migrateMediaScreen } from './codemods/migrate-media-screen'
 import { migrateMissingLayers } from './codemods/migrate-missing-layers'
 import { migrateTailwindDirectives } from './codemods/migrate-tailwind-directives'
-import { Stylesheet, type StylesheetId } from './stylesheet'
+import { Stylesheet, type StylesheetConnection, type StylesheetId } from './stylesheet'
 import { resolveCssId } from './utils/resolve'
 import { walk, WalkAction } from './utils/walk'
 
@@ -43,6 +43,8 @@ export async function migrate(stylesheet: Stylesheet, options: MigrateOptions) {
     throw new Error('Cannot migrate a stylesheet without a file path')
   }
 
+  if (!stylesheet.canMigrate) return
+
   await migrateContents(stylesheet, options)
 }
 
@@ -123,6 +125,57 @@ export async function analyze(stylesheets: Stylesheet[]) {
 
     await processor.process(sheet.root, { from: sheet.file })
   }
+
+  let commonPath = process.cwd()
+
+  function pathToString(path: StylesheetConnection[]) {
+    let parts: string[] = []
+
+    for (let connection of path) {
+      if (!connection.item.file) continue
+
+      let filePath = connection.item.file.replace(commonPath, '')
+      let layers = connection.meta.layers.join(', ')
+
+      if (layers.length > 0) {
+        parts.push(`${filePath} (layers: ${layers})`)
+      } else {
+        parts.push(filePath)
+      }
+    }
+
+    return parts.join(' <- ')
+  }
+
+  let lines: string[] = []
+
+  for (let sheet of stylesheets) {
+    if (!sheet.file) continue
+
+    let { convertablePaths, nonConvertablePaths } = sheet.analyzeImportPaths()
+    let isAmbiguous = convertablePaths.length > 0 && nonConvertablePaths.length > 0
+
+    if (!isAmbiguous) continue
+
+    sheet.canMigrate = false
+
+    let filePath = sheet.file.replace(commonPath, '')
+
+    for (let path of convertablePaths) {
+      lines.push(`- ${filePath} <- ${pathToString(path)}`)
+    }
+
+    for (let path of nonConvertablePaths) {
+      lines.push(`- ${filePath} <- ${pathToString(path)}`)
+    }
+  }
+
+  if (lines.length === 0) return
+
+  let error = `You have one or more stylesheets that are imported into a utility layer and non-utility layer.\n`
+  error += `We cannot convert stylesheets under these conditions. Please look at the following stylesheets:\n`
+
+  throw new Error(error + lines.join('\n'))
 }
 
 export async function split(stylesheets: Stylesheet[]) {

packages/@tailwindcss-upgrade/src/stylesheet.ts

@@ -42,6 +42,11 @@ export class Stylesheet {
    */
   children = new Set<StylesheetConnection>()
 
+  /**
+   * Whether or not this stylesheet can be migrated
+   */
+  canMigrate = true
+
   /**
    * Whether or not this stylesheet can be migrated
    */
@@ -123,6 +128,97 @@ export class Stylesheet {
     return layers
   }
 
+  /**
+   * Iterate all paths from a stylesheet through its ancestors to all roots
+   *
+   * For example, given the following structure:
+   *
+   * ```
+   * c.css
+   *  -> a.1.css @import "…"
+   *      -> a.css
+   *          -> root.1.css (utility: no)
+   *          -> root.2.css (utility: no)
+   *      -> b.css
+   *          -> root.1.css (utility: no)
+   *          -> root.2.css (utility: no)
+   *
+   *  -> a.2.css @import "…" layer(foo)
+   *      -> a.css
+   *          -> root.1.css (utility: no)
+   *          -> root.2.css (utility: no)
+   *      -> b.css
+   *          -> root.1.css (utility: no)
+   *          -> root.2.css (utility: no)
+   *
+   *  -> b.1.css @import "…" layer(components / utilities)
+   *      -> a.css
+   *          -> root.1.css (utility: yes)
+   *          -> root.2.css (utility: yes)
+   *      -> b.css
+   *          -> root.1.css (utility: yes)
+   *          -> root.2.css (utility: yes)
+   * ```
+   *
+   * We can see there are a total of 12 import paths with various layers.
+   * We need to be able to iterate every one of these paths and inspect
+   * the layers used in each path..
+   */
+  *pathsToRoot(): Iterable<StylesheetConnection[]> {
+    for (let { item, path } of walkDepth(this, (sheet) => sheet.parents)) {
+      // Skip over intermediate stylesheets since all paths from a leaf to a
+      // root will encompass all possible intermediate stylesheet paths.
+      if (item.parents.size > 0) {
+        continue
+      }
+
+      yield path
+    }
+  }
+
+  /**
+   * Analyze a stylesheets import paths to see if some can be considered
+   * for conversion to utility rules and others can't.
+   *
+   * If a stylesheet is imported directly or indirectly and some imports are in
+   * a utility layer and some are not that means that we can't safely convert
+   * the rules in the stylesheet to `@utility`. Doing so would mean that we
+   * would need to replicate the stylesheet and change one to have `@utility`
+   * rules and leave the other as is.
+   *
+   * We can see, given the same structure from the `pathsToRoot` example, that
+   * `css.css` is imported into different layers:
+   * - `a.1.css` has no layers and should not be converted
+   * - `a.2.css` has a layer `foo` and should not be converted
+   * - `b.1.css` has a layer `utilities` (or `components`) which should be
+   *
+   * Since this means that `c.css` must both not be converted and converted
+   * we can't do this without replicating the stylesheet, any ancestors, and
+   * adjusting imports which is a non-trivial task.
+   */
+  analyzeImportPaths() {
+    let convertablePaths: StylesheetConnection[][] = []
+    let nonConvertablePaths: StylesheetConnection[][] = []
+
+    for (let path of this.pathsToRoot()) {
+      let isConvertable = false
+
+      for (let { meta } of path) {
+        for (let layer of meta.layers) {
+          isConvertable ||= layer === 'utilities' || layer === 'components'
+        }
+      }
+
+      if (isConvertable) {
+        convertablePaths.push(path)
+      } else {
+        nonConvertablePaths.push(path)
+      }
+    }
+
+    return { convertablePaths, nonConvertablePaths }
+  }
+
   [util.inspect.custom]() {
     return {
       ...this,