feat(css): join adjacent rules and fold four more value spellings - #21648

test/CssSyntax.unittest.js (2)

2393-2403: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Give this block a distinct title.

Line 2401 uses the title template "keeps both rules where %s". Line 2318 already uses the same template in the same describe. Two cases can then report identical names. Rename the second block to name the nesting condition.

♻️ Proposed rename

-		])("keeps both rules where %s", (_name, css) => {
+		])("keeps both nested rules where %s", (_name, css) => {

---

2167-2169: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Two new inline comments exceed the comment-length limit. The guideline allows one line, and two short lines at most. Both comments span three lines.

• test/CssSyntax.unittest.js#L2167-L2169: shorten the <bg-image> slot explanation to two short lines.
• test/SyntaxBrowserEquivalence.unittest.js#L1024-L1026: shorten the adjacent-repeat explanation to two short lines.

As per coding guidelines: "Keep comments as short as possible, generally one line and no more than two short lines; comments must add non-obvious information and must not narrate or restate code."

Source: Coding guidelines

test/configCases/css/minimize-nesting/webpack.config.js (1)

25-25: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Use the specific Compiler JSDoc type.

EXPECTED_ANY disables type checking at the MinimizerPlugin.apply boundary. Replace it with import("../../../../").Compiler, if that type is compatible with the installed plugin declaration.

Proposed change

- }).apply(/** `@type` {EXPECTED_ANY} */ (compiler));
+ }).apply(/** `@type` {import("../../../../").Compiler} */ (compiler));

As per coding guidelines, use EXPECTED_ANY only when a precise type is genuinely unavailable.

Source: Coding guidelines

lib/css/syntax.js (3)

6643-6653: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Use the CC_ character-code constants.

This loop compares against the numeric literals 0x28 and 0x29. The file names character codes elsewhere, for example CC_SEMICOLON at Line 7964 and CC_QUOTATION_MARK at Line 5739. Use the same named constants for ( and ) if they exist in this module.

---

7646-7653: 🚀 Performance & Scalability | 🔵 Trivial | ⚡ Quick win

Chain the two gradient transforms instead of returning after the first.

_dropDefaultGradientDirection returns as soon as it changes anything, so _foldGradientStops never runs on the same value. For linear-gradient(to bottom,red,blue 100%) the default direction is dropped and the redundant 100% is kept, because the printer visits the node once.

Feed the first result into the second.

♻️ Proposed change

-				const gradient = _dropDefaultGradientDirection(fn, inner);
-				if (gradient !== null) return `${name}(${gradient})`;
-				const stops = _foldGradientStops(
-					fn,
-					inner,
-					_doublePositionAllowed(writer)
-				);
-				if (stops !== null) return `${name}(${stops})`;
+				const gradient = _dropDefaultGradientDirection(fn, inner);
+				const args = gradient === null ? inner : gradient;
+				const stops = _foldGradientStops(
+					fn,
+					args,
+					_doublePositionAllowed(writer)
+				);
+				if (stops !== null) return `${name}(${stops})`;
+				if (gradient !== null) return `${name}(${gradient})`;

---

7934-7952: 🚀 Performance & Scalability | 🔵 Trivial | 💤 Low value

Skip the allocation when the rule cannot contain a duplicate.

superseded and seen are allocated for every minified rule, including the many rules that hold zero or one item. The printer runs once per rule, so this is a hot path.

Guard both allocations on items.length >= 2.

♻️ Proposed change

 			/** `@type` {Set<number> | null} */
 			let superseded = null;
-			if (minify) {
+			if (minify && items.length >= 2) {
 				superseded = new Set();

As per coding guidelines: "Evaluate time and memory costs of changes, especially on hot paths."

Source: Coding guidelines

lib/css/syntax.js (2)

6612-6613: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Use full identifier names.

Rename fn and out to names such as functionName and reducedFunction.

As per coding guidelines, “Spell function, variable, parameter, and property names out in full.”

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@lib/css/syntax.js` around lines 6612 - 6613, In _reduceTransformFunctionDeep,
rename the abbreviated parameter fn and local variable out to full descriptive
identifiers such as functionName and reducedFunction, updating all references
while preserving the existing behavior.

Source: Coding guidelines

---

6575-6577: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Shorten these source comments.

• lib/css/syntax.js#L6575-L6577: Reduce the comment to one or two short lines.
• lib/css/syntax.js#L6588-L6590: Reduce the comment to one or two short lines.
• lib/css/syntax.js#L6605-L6607: Reduce the comment to one or two short lines.
• lib/css/syntax.js#L6660-L6662: Reduce the comment to one or two short lines.

As per coding guidelines, comments must generally use one line and no more than two short lines.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@lib/css/syntax.js` around lines 6575 - 6577, Shorten the source comments at
lib/css/syntax.js lines 6575-6577, 6588-6590, 6605-6607, and 6660-6662 to one or
two concise lines while preserving their essential clarification.

Source: Coding guidelines

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

tooling/generate-css-data.js (1)

792-794: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Shorten this comment.

Use no more than two short lines for this comment.

Proposed change

-			// A grammar naming its slots by type rather than by property: the slot
-			// is the longhand whose own value is exactly that type, followed
-			// through the `<'other'>` some of them are stated as.
+			// Match a type slot to the unique longhand whose complete value has that type.
+			// Follow a `<'other'>` reference before matching.

As per coding guidelines, "{lib,hot,tooling,test}/**/*.{js,mjs}: Keep comments as short as possible, generally one line and no more than two short lines; comments must add non-obvious information and must not narrate or restate code."

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@tooling/generate-css-data.js` around lines 792 - 794, Shorten the comment
near the grammar slot handling to no more than two brief lines, retaining only
the non-obvious explanation that the slot is the longhand whose value matches
the grammar type.

Source: Coding guidelines

test/SyntaxBrowserEquivalence.unittest.js (1)

432-435: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Shorten the changed comments.

Reduce these comments to no more than two short lines each. Keep only the cascade behavior that is not clear from the code.

As per coding guidelines, “Keep comments as short as possible, generally one line and no more than two short lines; comments must add non-obvious information and must not narrate or restate code.”

Also applies to: 443-447

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@test/SyntaxBrowserEquivalence.unittest.js` around lines 432 - 435, Shorten
the comments around the selector cascade behavior near the existing probe
explanation, including the related comment at the other referenced section, to
no more than two short lines each. Retain only the non-obvious rule that later
declarations win and !important declarations take precedence; remove narrative
about joining blocks, text folding, or restating the code.

Source: Coding guidelines

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes