[Rohan-Dedhia]

Fixes #20682.

Summary

When an entry stylesheet and an imported stylesheet are located on different Windows drive letters (or different UNC shares), path.posix.relative treats drive letters as regular directory names. This causes rebaseUrl to emit a drive-climbing path like url("../../../../../../../H:/.../images/probe.svg") when trying to relate paths across drives.

In this PR:

• Detect when root and base have different roots (such as different Windows drive letters or UNC shares) using path.win32.parse(). When they are on different drives, there is no valid relative path between them, so rebaseUrl preserves the resolved absolute URL.
• Normalize drive letter casing so same-drive comparisons (e.g. c: vs C:) continue to rebase relatively without generating ../ prefixes.
• Return already-absolute Windows paths early, matching the existing behavior for / root paths.

Test plan

Added unit tests in packages/@tailwindcss-node/src/urls.test.ts:

• Tested cross-drive URL rewriting (C: root with H: base) to verify the absolute URL is retained.
• Tested same-drive URL rewriting with differing drive letter casing (c: vs C:) to ensure relative rebasing is preserved.
• Tested parent directory navigation (../) on cross-drive stylesheets to ensure resolution keeps the correct path.
• Tested already-absolute Windows drive paths in url() to verify they are preserved.

Ran vitest across @tailwindcss-node:
All 12 tests in @tailwindcss-node passed.

[greptile-apps]

Confidence Score: 5/5

[Medium impact] The PR appears safe to merge; no blocking issues remain.

_{Reviews (5) · Last reviewed commit: "Preserve drive and UNC share roots when ..." · Reviewed by Greptile}

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Walkthrough

The URL rebasing logic now recognizes Windows-absolute URLs and compares normalized Windows roots. When the roots differ, it returns the joined absolute path. When the roots match, it computes a relative URL. Path normalization now recognizes network-share paths with either slash form. Tests cover cross-drive paths, drive-letter case differences, parent-directory references, absolute drive URLs, UNC paths, and escaped spaces.

Severity of issue fixed: Medium

Merge Risk: Minimal · up to 45bbd

The previously reported UNC rebasing risk is addressed. No actionable risk introduced by this PR remains after normal checks.

Pre-merge checks: 4

Check name	Status	Explanation
Title check		The title names the main change: rebasing URLs in stylesheets no longer climbs across Windows drives. It matches the changeset, which detects differing drive roots and UNC shares in rebaseUrl and pres…
Description check		The description states the problem (cross-drive relative paths producing drive-climbing URLs), the fix (differing-root detection, drive-letter casing normalization, early return for absolute Windows p…
Linked Issues check		[#20682] requires that cross-drive stylesheet rebasing avoid drive-climbing relative paths. The issue accepts either the retained absolute URL or a path that keeps the drive. Code at head (whole-PR d…
Out of Scope Changes check		The whole-PR diff changes three files, and each connects to [#20682]. - urls.ts: changes rebaseUrl and adds getPathRoot, normalizeRootVolume, and joinWithBase for cross-drive and UNC roots. …

Full details: Title check

Explanation

The title names the main change: rebasing URLs in stylesheets no longer climbs across Windows drives. It matches the changeset, which detects differing drive roots and UNC shares in rebaseUrl and preserves the absolute URL. The title is concise and specific.

Full details: Description check

Explanation

The description states the problem (cross-drive relative paths producing drive-climbing URLs), the fix (differing-root detection, drive-letter casing normalization, early return for absolute Windows paths), and the tests added in urls.test.ts. It relates directly to the changeset.

Full details: Linked Issues check

Explanation

[#20682] requires that cross-drive stylesheet rebasing avoid drive-climbing relative paths. The issue accepts either the retained absolute URL or a path that keeps the drive.

Code at head (whole-PR diff, merge base 9b2c925 to head 45bbd8d):

• rebaseUrl in packages/@tailwindcss-node/src/urls.ts computes getPathRoot for root and base with path.win32.parse. When the roots differ, it returns the joined absolute URL and skips path.posix.relative. This resolves the cross-drive case (for example C: root and H: base).
• Same-drive inputs still reach path.posix.relative, so output stays relative.
• normalizeRootVolume uppercases drive letters, so c: and C: compare equal.
• Already-absolute Windows URLs return early through path.win32.isAbsolute(url).
• UNC roots compare by lowercased server and share prefix. normalize-path.ts now also treats // prefixes as network-share paths.

Tests at head in urls.test.ts cover: cross-drive output (H:/tw-repro/app/images/probe.svg), parent navigation across drives, c: versus C: same-drive rebasing, already-absolute drive URLs, cross-share and same-share UNC cases, and drive-to-drive parent traversal.

The tests were not executed in this assessment. The 12-test pass result is author-reported. The test expectations match the code paths above on source reading.

Full details: Out of Scope Changes check

Explanation

The whole-PR diff changes three files, and each connects to [#20682].

• urls.ts: changes rebaseUrl and adds getPathRoot, normalizeRootVolume, and joinWithBase for cross-drive and UNC roots. This is the issue scope.
• urls.test.ts: adds regression tests for the new branches. This is supporting test coverage.
• normalize-path.ts: extends the existing UNC prefix check from \\ to also cover //. The UNC tests in urls.test.ts exercise this path, so the change supports the issue scope.

The test CSS escape backslashes in URLs are preserved on Windows paths guards the new same-drive path against changing backslash escapes. It adds no unrelated behavior. No unrelated feature or file change appears in the diff.

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⚠️ Outside diff range comments (1)

Major · Calculate same-share UNC paths without case-sensitive root segments. · urls.ts:130

packages/@tailwindcss-node/src/urls.ts:130
Major · Functional Correctness · Quick win

Calculate same-share UNC paths without case-sensitive root segments.

If root is //server/share/app and base is //SERVER/SHARE/app/styles, getPathRoot treats them as the same share. path.posix.relative still treats the differently cased share segments as different directories. It emits a path such as ../../../SERVER/SHARE/app/styles/images/probe.svg, which does not point to the asset when resolved from the UNC share. Use a case-insensitive Windows relative-path calculation for same-share UNC paths, then convert its separators for CSS. (raw.githubusercontent.com)

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[Rohan-Dedhia]

Addressed CodeRabbit's note in 4ab2521:

• When
  oot and �ase reside on the same Windows drive or UNC share, we now use path.win32.relative(normalizedRoot, absoluteUrl).replaceAll('\', '/') to perform case-insensitive relative path resolution. This prevents differently-cased root/share segments (e.g. //server/share vs //SERVER/SHARE) from producing extraneous climbing paths.
• Added regression test same-share UNC paths with differing casing rebase relatively without duplicate segments in packages/@tailwindcss-node/src/urls.test.ts.

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Actionable comments posted: 1

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