Fix crash during upgrade when content globs escape root of project (#14896)

This PR fixes an issue where globs in you `content` configuration escape
the current "root" of the project.

This can happen if you have a folder, and you need to look up in the
tree (e.g.: when looking at another package in a monorepo, or in case of
a Laravel project where you want to look at mail templates).

This applies a similar strategy we already implement on the Rust side.

1. Expand braces in the globs
2. Move static parts of the `pattern` to the `base` of the glob entry
object

---

Given a project setup like this:
```
.
├── admin
│   ├── my-tailwind.config.ts
│   └── src
│       ├── abc.jpg
│       ├── index.html
│       ├── index.js
│       └── styles
│           └── input.css
├── dashboard
│   ├── src
│   │   ├── index.html
│   │   ├── index.js
│   │   ├── input.css
│   │   └── pickaday.css
│   └── tailwind.config.ts
├── package-lock.json
├── package.json
├── postcss.config.js
└── unrelated
    └── index.html

7 directories, 14 files
```


If you then have this config:
```ts
// admin/my-tailwind.config.ts
export default {
  content: {
    relative: true,
    files: ['./src/**/*.html', '../dashboard/src/**/*.html'],
                            //  ^^  this is the important part, which escapes
                            //      the current root of the project.
  },
  theme: {
    extend: {
      colors: {
        primary: 'red',
      },
    },
  },
}
```


Then before this change, running the command looks like this:
<img width="1760" alt="image"
src="https://github.com/user-attachments/assets/60e2dfc7-3751-4432-80e3-8b4b8f1083d4">


After this change, running the command looks like this:
<img width="1452" alt="image"
src="https://github.com/user-attachments/assets/5c47182c-119c-4732-a253-2dace7086049">

---------

Co-authored-by: Philipp Spiess <hello@philippspiess.com>

Author: RobinMalfait

CHANGELOG.md

@@ -29,6 +29,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Ensure adjacent rules are merged together after handling nesting when generating optimized CSS ([#14873](https://github.com/tailwindlabs/tailwindcss/pull/14873))
 - _Upgrade (experimental)_: Install `@tailwindcss/postcss` next to `tailwindcss` ([#14830](https://github.com/tailwindlabs/tailwindcss/pull/14830))
 - _Upgrade (experimental)_: Remove whitespace around `,` separator when print arbitrary values ([#14838](https://github.com/tailwindlabs/tailwindcss/pull/14838))
+- _Upgrade (experimental)_: Fix crash during upgrade when content globs escape root of project ([#14896](https://github.com/tailwindlabs/tailwindcss/pull/14896))
 
 ### Changed
 

integrations/upgrade/js-config.test.ts

@@ -1,3 +1,4 @@
+import path from 'node:path'
 import { describe, expect } from 'vitest'
 import { css, html, json, test, ts } from '../utils'
 
@@ -938,6 +939,98 @@ test(
   },
 )
 
+test(
+  'migrate sources when pointing to folders outside the project root',
+  {
+    fs: {
+      'package.json': json`
+        {
+          "dependencies": {
+            "@tailwindcss/upgrade": "workspace:^"
+          }
+        }
+      `,
+
+      'frontend/tailwind.config.ts': ts`
+        export default {
+          content: {
+            relative: true,
+            files: ['./src/**/*.html', '../backend/mails/**/*.blade.php'],
+          },
+          theme: {
+            extend: {
+              colors: {
+                primary: 'red',
+              },
+            },
+          },
+        }
+      `,
+      'frontend/src/input.css': css`
+        @tailwind base;
+        @tailwind components;
+        @tailwind utilities;
+        @config "../tailwind.config.ts";
+      `,
+      'frontend/src/index.html': html`<div class="!text-primary"></div>`,
+
+      'backend/mails/welcome.blade.php': html`<div class="!text-primary"></div>`,
+    },
+  },
+  async ({ root, exec, fs }) => {
+    await exec('npx @tailwindcss/upgrade', {
+      cwd: path.join(root, 'frontend'),
+    })
+
+    expect(await fs.dumpFiles('frontend/**/*.css')).toMatchInlineSnapshot(`
+      "
+      --- frontend/src/input.css ---
+      @import 'tailwindcss';
+
+      @source '../../backend/mails/**/*.blade.php';
+
+      @theme {
+        --color-primary: red;
+      }
+
+      /*
+        The default border color has changed to \`currentColor\` in Tailwind CSS v4,
+        so we've added these compatibility styles to make sure everything still
+        looks the same as it did with Tailwind CSS v3.
+
+        If we ever want to remove these styles, we need to add an explicit border
+        color utility to any element that depends on these defaults.
+      */
+      @layer base {
+        *,
+        ::after,
+        ::before,
+        ::backdrop,
+        ::file-selector-button {
+          border-color: var(--color-gray-200, currentColor);
+        }
+      }
+
+      /*
+        Form elements have a 1px border by default in Tailwind CSS v4, so we've
+        added these compatibility styles to make sure everything still looks the
+        same as it did with Tailwind CSS v3.
+
+        If we ever want to remove these styles, we need to add \`border-0\` to
+        any form elements that shouldn't have a border.
+      */
+      @layer base {
+        input:where(:not([type='button'], [type='reset'], [type='submit'])),
+        select,
+        textarea {
+          border-width: 0;
+        }
+      }
+      "
+    `)
+  },
+)
+
 describe('border compatibility', () => {
   test(
     'migrate border compatibility',

packages/@tailwindcss-upgrade/package.json

@@ -29,6 +29,7 @@
   "dependencies": {
     "@tailwindcss/node": "workspace:^",
     "@tailwindcss/oxide": "workspace:^",
+    "braces": "^3.0.3",
     "dedent": "1.5.3",
     "enhanced-resolve": "^5.17.1",
     "globby": "^14.0.2",
@@ -44,6 +45,7 @@
     "tree-sitter-typescript": "^0.23.0"
   },
   "devDependencies": {
+    "@types/braces": "^3.0.4",
     "@types/node": "catalog:",
     "@types/postcss-import": "^14.0.3"
   }

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

@@ -21,6 +21,7 @@ import { migrate as migrateTemplate } from './template/migrate'
 import { prepareConfig } from './template/prepare-config'
 import { args, type Arg } from './utils/args'
 import { isRepoDirty } from './utils/git'
+import { hoistStaticGlobParts } from './utils/hoist-static-glob-parts'
 import { pkg } from './utils/packages'
 import { eprintln, error, header, highlight, info, success } from './utils/renderer'
 
@@ -143,11 +144,11 @@ async function run() {
       info('Migrating templates using the provided configuration file.')
       for (let config of configBySheet.values()) {
         let set = new Set<string>()
-        for (let { pattern, base } of config.globs) {
-          let files = await globby([pattern], {
+        for (let globEntry of config.globs.flatMap((entry) => hoistStaticGlobParts(entry))) {
+          let files = await globby([globEntry.pattern], {
             absolute: true,
             gitignore: true,
-            cwd: base,
+            cwd: globEntry.base,
           })
 
           for (let file of files) {

packages/@tailwindcss-upgrade/src/utils/hoist-static-glob-parts.test.ts

@@ -0,0 +1,48 @@
+import { expect, it } from 'vitest'
+import { hoistStaticGlobParts } from './hoist-static-glob-parts'
+
+it.each([
+  // A basic glob
+  [
+    { base: '/projects/project-a', pattern: './src/**/*.html' },
+    [{ base: '/projects/project-a/src', pattern: '**/*.html' }],
+  ],
+
+  // A glob pointing to a folder should result in `**/*`
+  [
+    { base: '/projects/project-a', pattern: './src' },
+    [{ base: '/projects/project-a/src', pattern: '**/*' }],
+  ],
+
+  // A glob pointing to a file, should result in the file as the pattern
+  [
+    { base: '/projects/project-a', pattern: './src/index.html' },
+    [{ base: '/projects/project-a/src', pattern: 'index.html' }],
+  ],
+
+  // A glob going up a directory, should result in the new directory as the base
+  [
+    { base: '/projects/project-a', pattern: '../project-b/src/**/*.html' },
+    [{ base: '/projects/project-b/src', pattern: '**/*.html' }],
+  ],
+
+  // A glob with curlies, should be expanded to multiple globs
+  [
+    { base: '/projects/project-a', pattern: '../project-{b,c}/src/**/*.html' },
+    [
+      { base: '/projects/project-b/src', pattern: '**/*.html' },
+      { base: '/projects/project-c/src', pattern: '**/*.html' },
+    ],
+  ],
+  [
+    { base: '/projects/project-a', pattern: '../project-{b,c}/src/**/*.{js,html}' },
+    [
+      { base: '/projects/project-b/src', pattern: '**/*.js' },
+      { base: '/projects/project-b/src', pattern: '**/*.html' },
+      { base: '/projects/project-c/src', pattern: '**/*.js' },
+      { base: '/projects/project-c/src', pattern: '**/*.html' },
+    ],
+  ],
+])('should hoist the static parts of the glob: %s', (input, output) => {
+  expect(hoistStaticGlobParts(input)).toEqual(output)
+})

packages/@tailwindcss-upgrade/src/utils/hoist-static-glob-parts.ts

@@ -0,0 +1,79 @@
+import braces from 'braces'
+import path from 'node:path'
+
+interface GlobEntry {
+  base: string
+  pattern: string
+}
+
+export function hoistStaticGlobParts(entry: GlobEntry): GlobEntry[] {
+  return braces(entry.pattern, { expand: true }).map((pattern) => {
+    let clone = { ...entry }
+    let [staticPart, dynamicPart] = splitPattern(pattern)
+
+    // Move static part into the `base`.
+    if (staticPart !== null) {
+      clone.base = path.resolve(entry.base, staticPart)
+    } else {
+      clone.base = path.resolve(entry.base)
+    }
+
+    // Move dynamic part into the `pattern`.
+    if (dynamicPart === null) {
+      clone.pattern = '**/*'
+    } else {
+      clone.pattern = dynamicPart
+    }
+
+    // If the pattern looks like a file, move the file name from the `base` to
+    // the `pattern`.
+    let file = path.basename(clone.base)
+    if (file.includes('.')) {
+      clone.pattern = file
+      clone.base = path.dirname(clone.base)
+    }
+
+    return clone
+  })
+}
+
+// Split a glob pattern into a `static` and `dynamic` part.
+//
+// Assumption: we assume that all globs are expanded, which means that the only
+// dynamic parts are using `*`.
+//
+// E.g.:
+//  Original input: `../project-b/**/*.{html,js}`
+//  Expanded input: `../project-b/**/*.html` & `../project-b/**/*.js`
+//  Split on first input: ("../project-b", "**/*.html")
+//  Split on second input: ("../project-b", "**/*.js")
+function splitPattern(pattern: string): [staticPart: string | null, dynamicPart: string | null] {
+  // No dynamic parts, so we can just return the input as-is.
+  if (!pattern.includes('*')) {
+    return [pattern, null]
+  }
+
+  let lastSlashPosition: number | null = null
+
+  for (let i = 0; i < pattern.length; i++) {
+    let c = pattern[i];
+    if (c === '/') {
+      lastSlashPosition = i
+    }
+
+    if (c === '*' || c === '!') {
+      break
+    }
+  }
+
+  // Very first character is a `*`, therefore there is no static part, only a
+  // dynamic part.
+  if (lastSlashPosition === null) {
+    return [null, pattern]
+  }
+
+  let staticPart = pattern.slice(0, lastSlashPosition).trim()
+  let dynamicPart = pattern.slice(lastSlashPosition + 1).trim()
+
+  return [staticPart || null, dynamicPart || null]
+}