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Add an option 'preserveUndefinedVariables' to keeps undefined variables as is in final output #136

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Add an option 'preserveUndefinedVariables' to keeps undefined variables as is in final output #136

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6 changes: 6 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -375,6 +375,12 @@ Keeps your at-rules like media queries in the order to defined them.

Ideally, this would be defaulted to `true` and it will be in the next major version. All of the tests expecations need to be updated and probably just drop support for `preserveAtRulesOrder: false`

### `preserveUndefinedVariables` (default: `false`)
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@vithar Can you give an example of why undefined isn't desired and is conflicting?

Does the existing preserve: true option cover your use case? The undefined value will just fallback to the same preserved value your trying to keep around with this new option.

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@YoungL1107 YoungL1107 Feb 2, 2024 •
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image
If variable is undefined, the build result is width: undefined;.
And, preserve: true will make css file larger
maybe that's why


Whether to preserve the undefined variables in final output.

Setting this option to `true` leaves any undefined variables as is in output CSS.

# Quick Reference/Notes

- This plugin was spawned out of a [discussion on the `cssnext` repo](https://github.com/cssnext/cssnext/issues/99).
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7 changes: 5 additions & 2 deletions index.js
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Expand Up @@ -60,7 +60,9 @@ var defaults = {
preserveInjectedVariables: true,
// Will write media queries in the same order as in the original file.
// Currently defaulted to false for legacy behavior. We can update to `true` in a major version
preserveAtRulesOrder: false
preserveAtRulesOrder: false,
// Preserve undefined variables as is in final output.
preserveUndefinedVariables: false
};

module.exports = (options = {}) => {
Expand Down Expand Up @@ -158,7 +160,7 @@ module.exports = (options = {}) => {
eachCssVariableDeclaration(css, function(decl) {
var declParentRule = decl.parent;

var valueResults = logResolveValueResult(resolveValue(decl, map));
var valueResults = logResolveValueResult(resolveValue(decl, map, opts.preserveUndefinedVariables));
// Split out each selector piece into its own declaration for easier logic down the road
decl.parent.selectors.forEach(function(selector) {
// Create a detached clone
Expand Down Expand Up @@ -263,6 +265,7 @@ module.exports = (options = {}) => {
map,
opts.preserve,
opts.preserveAtRulesOrder,
opts.preserveUndefinedVariables,
logResolveValueResult
);
}
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6 changes: 3 additions & 3 deletions lib/resolve-decl.js
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Expand Up @@ -71,7 +71,7 @@ function eachMapItemDependencyOfDecl(variablesUsedList, map, decl, cb) {

// Resolve the decl with the computed value
// Also add in any media queries that change the value as necessary
function resolveDecl(decl, map, /*optional*/shouldPreserve, /*optional*/preserveAtRulesOrder, /*optional*/logResolveValueResult) {
function resolveDecl(decl, map, /*optional*/shouldPreserve, /*optional*/preserveAtRulesOrder, /*optional*/preserveUndefinedVariables, /*optional*/logResolveValueResult) {
shouldPreserve = (typeof shouldPreserve === "function" ? shouldPreserve(decl) : shouldPreserve) || false;
preserveAtRulesOrder = preserveAtRulesOrder || false;

Expand All @@ -88,7 +88,7 @@ function resolveDecl(decl, map, /*optional*/shouldPreserve, /*optional*/preserve

// Grab the balue for this declarations
//console.log('resolveDecl 1');
var valueResults = _logResolveValueResult(resolveValue(decl, map));
var valueResults = _logResolveValueResult(resolveValue(decl, map, preserveUndefinedVariables));


// Resolve the cascade dependencies
Expand All @@ -112,7 +112,7 @@ function resolveDecl(decl, map, /*optional*/shouldPreserve, /*optional*/preserve
}

// No mangle resolve
declClone.value = _logResolveValueResult(resolveValue(mimicDecl, map, true)).value;
declClone.value = _logResolveValueResult(resolveValue(mimicDecl, map, preserveUndefinedVariables, true)).value;

if(mapItem.isUnderAtRule) {
// Create the clean atRule for which we place the declaration under
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10 changes: 6 additions & 4 deletions lib/resolve-value.js
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Expand Up @@ -61,7 +61,7 @@ function balancedVar(value) {
// Note: We do not modify the declaration
// Note: Resolving a declaration value without any `var(...)` does not harm the final value.
// This means, feel free to run everything through this function
var resolveValue = function(decl, map, /*optional*/ignorePseudoScope, /*internal debugging*/_debugIsInternal) {
var resolveValue = function(decl, map, /*optional*/preserveUndefinedVariables, /*optional*/ignorePseudoScope, /*internal debugging*/_debugIsInternal) {
var debugIndent = _debugIsInternal ? '\t' : '';

var matchingVarDecl = undefined;
Expand Down Expand Up @@ -136,7 +136,7 @@ var resolveValue = function(decl, map, /*optional*/ignorePseudoScope, /*internal
var fallbackValue = fallback;
if(fallback) {
var fallbackDecl = decl.clone({ parent: decl.parent, value: fallback });
fallbackValue = resolveValue(fallbackDecl, map, false, /*internal*/true).value;
fallbackValue = resolveValue(fallbackDecl, map, preserveUndefinedVariables, false, /*internal*/true).value;
}

return fallbackValue;
Expand All @@ -153,7 +153,7 @@ var resolveValue = function(decl, map, /*optional*/ignorePseudoScope, /*internal
return ancestor === nodeToSpliceParentOnto;
});

replaceValue = resolveValue(matchingMimicDecl, map, false, /*internal*/true).value;
replaceValue = resolveValue(matchingMimicDecl, map, preserveUndefinedVariables, false, /*internal*/true).value;
}

isResultantValueUndefined = replaceValue === undefined;
Expand All @@ -167,7 +167,9 @@ var resolveValue = function(decl, map, /*optional*/ignorePseudoScope, /*internal

return {
// The resolved value
value: !isResultantValueUndefined ? resultantValue : undefined,
value: isResultantValueUndefined ?
(preserveUndefinedVariables ? decl.value : undefined) :
resultantValue,
// Array of variable names used in resolving this value
variablesUsed: variablesUsedInValue,
// Any warnings generated from parsing this value
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