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Feature/inequality operator #4454

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99f0ba8
fix: resolve lint and style errors in compiler and build tools
Ritvik718 Jun 15, 2026
a1edc9c
feat: add inequality comparison operator (!=)
Ritvik718 Jun 15, 2026
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219 changes: 109 additions & 110 deletions packages/less/benchmark/benchmark-runner.js
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Original file line number Diff line number Diff line change
Expand Up @@ -14,58 +14,58 @@ var extraOpts = {};

// Parse --key=value options from remaining args
for (var ai = 5; ai < process.argv.length; ai++) {
var optMatch = process.argv[ai].match(/^--([a-z-]+)=(.*)$/);
if (optMatch) { extraOpts[optMatch[1]] = optMatch[2]; }
var optMatch = process.argv[ai].match(/^--([a-z-]+)=(.*)$/);
if (optMatch) { extraOpts[optMatch[1]] = optMatch[2]; }
}

if (!file) {
console.error('Usage: node benchmark-runner.js <file.less> [runs] [warmup]');
process.exit(1);
console.error('Usage: node benchmark-runner.js <file.less> [runs] [warmup]');
process.exit(1);
}

// Find Less compiler - try multiple paths for different version eras
var less;
var lessPath = '';
var tryPaths = [
// v4.x monorepo (after build)
'./packages/less',
// v3.x / v2.x (lib in repo)
'.',
'./lib/less-node',
// Fallback
'less'
// v4.x monorepo (after build)
'./packages/less',
// v3.x / v2.x (lib in repo)
'.',
'./lib/less-node',
// Fallback
'less'
];

for (var i = 0; i < tryPaths.length; i++) {
try {
var p = tryPaths[i];
// Use path.resolve for relative paths, but keep bare package names for Node resolution
var mod = require(p.startsWith('.') ? path.resolve(p) : p);
// Handle both direct export and .default (ESM interop)
less = mod && mod.default ? mod.default : mod;
if (less && (less.render || less.parse)) {
lessPath = p;
break;
}
less = null;
} catch (e) {
try {
var p = tryPaths[i];
// Use path.resolve for relative paths, but keep bare package names for Node resolution
var mod = require(p.startsWith('.') ? path.resolve(p) : p);
// Handle both direct export and .default (ESM interop)
less = mod && mod.default ? mod.default : mod;
if (less && (less.render || less.parse)) {
lessPath = p;
Comment on lines +46 to +47

@coderabbitai coderabbitai Bot Jun 15, 2026

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⚠️ Potential issue | 🟠 Major | ⚡ Quick win

Require render during compiler discovery to prevent runtime crashes.

At Line 46, discovery currently accepts compilers that only expose parse. But runOnce() always calls less.render (Line 93), so a parse-only module will fail at runtime with TypeError: less.render is not a function.

Proposed fix 
-        if (less && (less.render || less.parse)) {
+        if (less && typeof less.render === 'function') {
             lessPath = p;
             break;
         }
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
if (less && (less.render || less.parse)) {
lessPath = p;
if (less && typeof less.render === 'function') {
lessPath = p;
break;
}
🤖 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 `@packages/less/benchmark/benchmark-runner.js` around lines 46 - 47, The
compiler discovery condition at line 46 currently uses OR logic to accept
compilers that have either `render` or `parse`, but the `runOnce()` function
always calls `less.render` at line 93. Change the condition from `(less.render
|| less.parse)` to `(less.render && less.parse)` to require both methods to be
present, preventing runtime crashes when a parse-only compiler is selected.

break;
}
less = null;
} catch (e) {
// try next
}
}
}

if (!less) {
console.error(JSON.stringify({ error: 'Could not find Less compiler', tried: tryPaths }));
process.exit(2);
console.error(JSON.stringify({ error: 'Could not find Less compiler', tried: tryPaths }));
process.exit(2);
}

// Determine version
var version = 'unknown';
if (less.version) {
if (Array.isArray(less.version)) {
version = less.version.join('.');
} else {
version = String(less.version);
}
if (Array.isArray(less.version)) {
version = less.version.join('.');
} else {
version = String(less.version);
}
}

var filePath = path.resolve(file);
Expand All @@ -74,102 +74,101 @@ var fileDir = path.dirname(filePath);

// Use less.render() - stable across all versions
var renderTimes = [];
var parseTimes = [];
var completed = 0;
var errors = [];

function hrNow() {
var hr = process.hrtime();
return hr[0] * 1000 + hr[1] / 1e6;
var hr = process.hrtime();
return hr[0] * 1000 + hr[1] / 1e6;
}

function runOnce(callback) {
var start = hrNow();
var opts = {
filename: filePath,
paths: [fileDir]
};
// Forward extra options (e.g. --math=always)
for (var key in extraOpts) { opts[key] = extraOpts[key]; }
less.render(data, opts, function (err, output) {
var end = hrNow();
if (err) {
errors.push({ run: completed, error: err.message || String(err) });
callback(err);
return;
}
renderTimes.push(end - start);
completed++;
callback(null);
});
var start = hrNow();
var opts = {
filename: filePath,
paths: [fileDir]
};
// Forward extra options (e.g. --math=always)
for (var key in extraOpts) { opts[key] = extraOpts[key]; }
less.render(data, opts, function (err) {
var end = hrNow();
if (err) {
errors.push({ run: completed, error: err.message || String(err) });
callback(err);
return;
}
renderTimes.push(end - start);
completed++;
callback(null);
});
}

function runAll(i) {
if (i >= totalRuns) {
reportResults();
return;
}
runOnce(function (err) {
if (err && errors.length > 3) {
// Too many errors, bail
reportResults();
return;
if (i >= totalRuns) {
reportResults();
return;
}
runAll(i + 1);
});
runOnce(function (err) {
if (err && errors.length > 3) {
// Too many errors, bail
reportResults();
return;
}
runAll(i + 1);
});
}

function analyze(times, skipWarmup) {
var start = skipWarmup ? warmupRuns : 0;
if (times.length <= start) return null;
var effective = times.slice(start);
var total = 0, min = Infinity, max = 0;
for (var i = 0; i < effective.length; i++) {
total += effective[i];
min = Math.min(min, effective[i]);
max = Math.max(max, effective[i]);
}
var avg = total / effective.length;

// Median
var sorted = effective.slice().sort(function (a, b) { return a - b; });
var mid = Math.floor(sorted.length / 2);
var median = sorted.length % 2 ? sorted[mid] : (sorted[mid - 1] + sorted[mid]) / 2;

// Standard deviation and coefficient of variation
var sumSqDiff = 0;
for (var i = 0; i < effective.length; i++) {
sumSqDiff += (effective[i] - avg) * (effective[i] - avg);
}
var stddev = Math.sqrt(sumSqDiff / effective.length);
var variancePct = avg === 0 ? 0 : (stddev / avg) * 100;

return {
min: Math.round(min * 100) / 100,
max: Math.round(max * 100) / 100,
avg: Math.round(avg * 100) / 100,
median: Math.round(median * 100) / 100,
stddev: Math.round(stddev * 100) / 100,
variance_pct: Math.round(variancePct * 100) / 100,
samples: effective.length,
throughput_kbs: Math.round(1000 / avg * data.length / 1024)
};
var start = skipWarmup ? warmupRuns : 0;
if (times.length <= start) return null;
var effective = times.slice(start);
var total = 0, min = Infinity, max = 0;
for (var i = 0; i < effective.length; i++) {
total += effective[i];
min = Math.min(min, effective[i]);
max = Math.max(max, effective[i]);
}
var avg = total / effective.length;

// Median
var sorted = effective.slice().sort(function (a, b) { return a - b; });
var mid = Math.floor(sorted.length / 2);
var median = sorted.length % 2 ? sorted[mid] : (sorted[mid - 1] + sorted[mid]) / 2;

// Standard deviation and coefficient of variation
var sumSqDiff = 0;
for (i = 0; i < effective.length; i++) {
sumSqDiff += (effective[i] - avg) * (effective[i] - avg);
}
var stddev = Math.sqrt(sumSqDiff / effective.length);
var variancePct = avg === 0 ? 0 : (stddev / avg) * 100;

return {
min: Math.round(min * 100) / 100,
max: Math.round(max * 100) / 100,
avg: Math.round(avg * 100) / 100,
median: Math.round(median * 100) / 100,
stddev: Math.round(stddev * 100) / 100,
variance_pct: Math.round(variancePct * 100) / 100,
samples: effective.length,
throughput_kbs: Math.round(1000 / avg * data.length / 1024)
};
}

function reportResults() {
var result = {
version: version,
lessPath: lessPath,
file: path.basename(file),
fileSize: data.length,
fileSizeKB: Math.round(data.length / 1024 * 10) / 10,
totalRuns: totalRuns,
warmupRuns: warmupRuns,
completedRuns: completed,
errors: errors.length > 0 ? errors : undefined,
render: analyze(renderTimes, true)
};
console.log(JSON.stringify(result));
var result = {
version: version,
lessPath: lessPath,
file: path.basename(file),
fileSize: data.length,
fileSizeKB: Math.round(data.length / 1024 * 10) / 10,
totalRuns: totalRuns,
warmupRuns: warmupRuns,
completedRuns: completed,
errors: errors.length > 0 ? errors : undefined,
render: analyze(renderTimes, true)
};
console.log(JSON.stringify(result));
}

runAll(0);
2 changes: 1 addition & 1 deletion packages/less/build/rollup.js
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Original file line number Diff line number Diff line change
Expand Up @@ -28,7 +28,7 @@ function moduleShim() {
},
load(id) {
if (id === '\0module') {
return `export function createRequire() { return require; }`;
return 'export function createRequire() { return require; }';
}
return null;
}
Expand Down
3 changes: 3 additions & 0 deletions packages/less/lib/less/parser/parser.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2547,6 +2547,9 @@ const Parser = function Parser(context, imports, fileInfo, currentIndex) {
op = '<';
}
} else
if (parserInput.$str('!=')) {
op = '!=';
} else
if (parserInput.$char('=')) {
if (parserInput.$char('>')) {
op = '=>';
Expand Down
6 changes: 3 additions & 3 deletions packages/less/lib/less/tree/condition.js
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Original file line number Diff line number Diff line change
Expand Up @@ -45,16 +45,16 @@ class Condition extends Node {
default:
switch (Node.compare(a, b)) {
case -1:
result = this.op === '<' || this.op === '=<' || this.op === '<=';
result = this.op === '<' || this.op === '=<' || this.op === '<=' || this.op === '!=';
break;
case 0:
result = this.op === '=' || this.op === '>=' || this.op === '=<' || this.op === '<=';
break;
case 1:
result = this.op === '>' || this.op === '>=';
result = this.op === '>' || this.op === '>=' || this.op === '!=';
break;
default:
result = false;
result = this.op === '!=';
}
}

Expand Down
6 changes: 6 additions & 0 deletions packages/test-data/tests-unit/css-guards/css-guards.css
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Original file line number Diff line number Diff line change
Expand Up @@ -35,3 +35,9 @@
sub-prop: 2px;
prop: 1px;
}
.inequality-test-1 {
color: green;
}
.inequality-test-3 {
color: green;
}
13 changes: 13 additions & 0 deletions packages/test-data/tests-unit/css-guards/css-guards.less
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Original file line number Diff line number Diff line change
Expand Up @@ -101,4 +101,17 @@
}
a:hover when (2 = true) {5:-}

.inequality-test-1 when (2 != 1) {
color: green;
}
.inequality-test-2 when (2 != 2) {
color: red;
}
.inequality-test-3 when (@b != 1) {
color: green;
}
.inequality-test-4 when (@b != 2) {
color: red;
}


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