clean-css ignore comments throw errors when source map is built

[dougludlow]

Possibly related to #1042. I noticed this while running a build with Angular CLI (ng build --prod --source-map). I was able to reproduce the issue with clean-css-cli and have provided details below.

Environment

• clean-css version: 4.2.1
• node.js version: v10.16.2
• operating system: macOS Majave 10.14.6

Reproducible code

echo "/* clean-css ignore:start */a { margin: 0px; }/* clean-css ignore:end */" | npx [email protected] --source-map -o ~/Desktop/style.css

Error

/Users/doug.ludlow/.npm/_npx/99367/lib/node_modules/clean-css-cli/node_modules/clean-css/lib/reader/apply-source-maps.js:72
    metadata = scope[2][0];
                       ^

TypeError: Cannot read property '0' of undefined
    at findTokenSource (/Users/doug.ludlow/.npm/_npx/99367/lib/node_modules/clean-css-cli/node_modules/clean-css/lib/reader/apply-source-maps.js:72:24)
    at doApplySourceMaps (/Users/doug.ludlow/.npm/_npx/99367/lib/node_modules/clean-css-cli/node_modules/clean-css/lib/reader/apply-source-maps.js:46:14)
    at applySourceMaps (/Users/doug.ludlow/.npm/_npx/99367/lib/node_modules/clean-css-cli/node_modules/clean-css/lib/reader/apply-source-maps.js:33:5)
    at Object.callback (/Users/doug.ludlow/.npm/_npx/99367/lib/node_modules/clean-css-cli/node_modules/clean-css/lib/reader/read-sources.js:25:12)
    at doInlineImports (/Users/doug.ludlow/.npm/_npx/99367/lib/node_modules/clean-css-cli/node_modules/clean-css/lib/reader/read-sources.js:200:25)
    at inline (/Users/doug.ludlow/.npm/_npx/99367/lib/node_modules/clean-css-cli/node_modules/clean-css/lib/reader/read-sources.js:178:10)
    at fromStyles (/Users/doug.ludlow/.npm/_npx/99367/lib/node_modules/clean-css-cli/node_modules/clean-css/lib/reader/read-sources.js:151:5)
    at fromString (/Users/doug.ludlow/.npm/_npx/99367/lib/node_modules/clean-css-cli/node_modules/clean-css/lib/reader/read-sources.js:48:10)
    at doReadSources (/Users/doug.ludlow/.npm/_npx/99367/lib/node_modules/clean-css-cli/node_modules/clean-css/lib/reader/read-sources.js:33:12)
    at readSources (/Users/doug.ludlow/.npm/_npx/99367/lib/node_modules/clean-css-cli/node_modules/clean-css/lib/reader/read-sources.js:24:10)

Possible solution

While debugging this issue, I found that code surrounded with /* clean-css ignore:<start|end> */ comments have a token type of raw (Token.RAW) and resemble a shape like this:

[ 'raw', 'a { margin: 0px; }', [ [ 1, 28, undefined ] ] ]

As such, the following line of code could probably be modified as follows:

https://github.com/jakubpawlowicz/clean-css/blob/3b2d0d23acf7582516a34f1f32e4dc84a830351a/lib/reader/apply-source-maps.js#L68

- if (token[0] == Token.AT_RULE || token[0] == Token.COMMENT) {
+ if (token[0] == Token.AT_RULE || token[0] == Token.COMMENT || token[0] == Token.RAW) {

However, I'm not exactly aware of the implications related to that associated change. Let me know if that change makes sense and if you'd like me to open a pull request.

[jakubpawlowicz]

Hey @dougludlow - I have just pushed a fix based on your suggestion. That was it! Many thanks for debugging it to that point!
The change will land in v5 soon #1135

Sorry for not taking care of this patch earlier, but I'm catching up with clean-css maintenance only now.