Transition shorthand property throws error because of sourcemaps (3.7.1)

[mahish]

Originally posted to gulp-less gulp-community/gulp-less#299. But the issue is with the LESS itself.

lessc 3.7.1 => Error with lessc --source-map=file.map styles.less styles.css:

SyntaxError: Cannot read property 'substring' of undefined in /Users/.../components/button.less on line 62, column 3:
61   cursor: pointer;
62   transition: background-color @duration-short @easing-out;
63   border-radius: @base-border-radius;

gulp-less 4.0.1 stacktrace of the error is telling more:

Potentially unhandled rejection [2] TypeError: Cannot read property 'substring' of undefined
    at SourceMapOutput.add (/Users/.../node_modules/less/lib/less/source-map-output.js:72:39)
    at Call.genCSS (/Users/.../node_modules/less/lib/less/tree/call.js:86:12)
    at Expression.genCSS (/Users/.../node_modules/less/lib/less/tree/expression.js:54:23)
    at Declaration.genCSS (/Users/.../node_modules/less/lib/less/tree/declaration.js:35:20)
    at Ruleset.genCSS (/Users/.../node_modules/less/lib/less/tree/ruleset.js:508:18)
    at Ruleset.genCSS (/Users/.../node_modules/less/lib/less/tree/ruleset.js:508:18)
    at SourceMapOutput.toCSS (/Users/.../node_modules/less/lib/less/source-map-output.js:123:24)
    at SourceMapBuilder.toCSS (/Users/.../node_modules/less/lib/less/source-map-builder.js:23:35)
    at ParseTree.toCSS (/Users/.../node_modules/less/lib/less/parse-tree.js:33:47)
    at /Users/.../node_modules/less/lib/less/render.js:35:40
    at /Users/.../node_modules/less/lib/less/parse.js:86:21
    at ImportVisitor.finish [as _finish] (/Users/.../node_modules/less/lib/less/parser/parser.js:240:28)
    at ImportVisitor._onSequencerEmpty (/Users/.../node_modules/less/lib/less/visitors/import-visitor.js:36:14)
    at ImportSequencer.tryRun (/Users/.../node_modules/less/lib/less/visitors/import-sequencer.js:50:14)
    at /Users/.../node_modules/less/lib/less/visitors/import-sequencer.js:19:25
    at fileParsedFunc (/Users/.../node_modules/less/lib/less/import-manager.js:63:17)
    at /Users/.../node_modules/less/lib/less/import-manager.js:137:25
    at finish (/Users/.../node_modules/less/lib/less/parser/parser.js:240:28)
    at Object.parse (/Users/.../node_modules/less/lib/less/parser/parser.js:248:24)
    at loadFileCallback (/Users/.../node_modules/less/lib/less/import-manager.js:136:68)
    at <anonymous>

It works fine without sourcemaps option.

[matthew-dean]

This looks related to #3300.

[mahish]

@matthew-dean Yeah. Looks like. So let me clarify my case.

I dont use CSS variables. Used LESS variables have the following values:

@duration-long: 0.62s;
@easing-out: cubic-bezier(0.2, 0.62, 0.38, 1);

There is no error, if I remove these variables from the transition shorthand property and use direct values instead.

[matthew-dean]

@mahish Can you see if this branch fixes your issue? https://github.com/matthew-dean/less.js/tree/bugfix-3300

[mahish]

@matthew-dean I did npm install matthew-dean/less.js#bugfix-3300 -g, then lessc --source-map=file.map styles.less styles.css in the folder and didnt get any error.

[matthew-dean]

@mahish Great! Thanks for letting me know!

[matthew-dean]

@mahish Does it appear to still be mapping lines correctly? I have no reason to think otherwise, just making sure.

[mahish]

I couldnt make sourcemaps work in the project (I dont think it is related to this issue). So I created new one (small and simple) for testing purposes. And so I can say lines are mapped correctly:)

[matthew-dean]

@mahish Great!

[matthew-dean]

v3.8.1 released