1306146 - Firefox handles relative sourceRoot in source maps incorrectly

Status: RESOLVED WORKSFORME

(DevTools :: Debugger, defect, P2)

Description

[DreamSonic]

User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:49.0) Gecko/20100101 Firefox/49.0
Build ID: 20160922113459

Steps to reproduce:

When a source map contains sourceRoot which represents a relative path, Firefox handles the sources paths incorrectly.

Example requires 3 files (2 if the source map is inlined):
1) Source file (http://example.com/foo/source/script.js)
2) File generated based on the source (http://example.com/foo/bundle.js)
3) Source map (http://example.com/foo/bundle.map)

Notice that the source file is located in a folder named `source` relative to the bundle.

The source map looks like this:
```
{"sources":["script.js"], "sourceRoot":"source", ...}
```

Here's a plunkr: https://plnkr.co/edit/ESu37NSP6Hs3xLxl9NLt?p=preview (Launch the preview in a separate window to reproduce the results.)


Actual results:

Instead of listing `http://example.com/foo/source/script.js` in the sources, dev tools show `http://example.com/source/script.js` - notice that `/foo` is missing, hence the URL is not correct.

(If the source map doesn't contain sourcesContent this will result in 404 when dev tools will try to load the file.)


Expected results:

According to the spec (https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit#heading=h.75yo6yoyk7x5):
> If the sources are not absolute URLs after prepending of the “sourceRoot”, the sources are resolved relative to the SourceMap (like resolving script src in a html document).

In this example the resulting source should be `http://example.com/foo/` + `source` + `script.js` = `http://example.com/foo/source/script.js`

I've confirmed that Chrome, IE11 and Edge work correctly in this case.

When sourceRoot is omitted (or empty) and the source is specified as `source/script.js` the issue is not reproducible and devtools work correctly

Comment 1

[DreamSonic]

Out of curiosity I've experimented with various combinations of sources and sourceRoot values. Let's say that the source map is located in `/foo/bar/baz.map`

source        | sourceRoot | resulting source
-----------------------------------------------
script.js     | (empty)    | /foo/bar/script.js
script.js     | "."        | /foo/script.js
script.js     | ".."       | /script.js
script.js     | "../qux"   | /qux/script.js
qux/script.js | (empty)    | /foo/bar/qux/script.js
qux/script.js | "."        | /foo/qux/script.js
qux/script.js | ".."       | /qux/script.js
qux/script.js | "../qux    | /qux/qux/script.js

My guess is that there's somewhere an off-by-one error in relative path calculation routine, because the paths appear to be relative not to the folder containing the source map, but to its parent.

Comment 2

[Bryan Clark (DevTools PM) [:clarkbw]]

Attachment: Screen Shot 2017-01-10 at 1.26.06 PM.png

This is what I'm seeing in Nightly, seems to work there.

Comment 3

[Bryan Clark (DevTools PM) [:clarkbw]]

Can you try this out in Nightly? http://nightly.mozilla.org/

Thanks!

Comment 4

[DreamSonic]

Bryan, yes, I've verified that it works correctly in Nightly (v53) and in Aurora/Dev Edition (v52).
This issue can be closed. Thanks!

Comment 5

[Bryan Clark (DevTools PM) [:clarkbw]]

Thanks!