gwt sourcemap: incorrect source line

[dankurka]

Originally reported on Google Code with ID 9103

Found in GWT Release (e.g. 2.4.0, 2.5.1, trunk): 2.7

Detailed description (please be as specific as possible):

code (https://gist.github.com/develar/fa092f4c9ef12325ecba, sample project attached):

public void onClick(ClickEvent event) {
                if (label.getText().equals("")) {
                    MySampleApplicationService.App.getInstance().getMessage("Hello,
World!", new MyAsyncCallback(label));
                } else {
                    label.setText("");
                }

                internalMethod();
            } !!! sourcemap entry is incorrect: source line 24 specified, but must
be 33. !!!

See attached screenshot.

Problem: IDEA cannot correctly map generated method param name to source. In any case
I implemented workaround on IDEA side, but GWT sourcemaps should be correct.

Reported by develar on 2015-01-17 14:34:54

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- _Attachment: [sample.zip](https://storage.googleapis.com/google-code-attachments/google-web-toolkit/issue-9103/comment-0/sample.zip)_ - _Attachment: Screen Shot 2015-01-17 at 15.23.26.png
_

[dankurka]

And, please note — GWT produces poor sourcemap. TypeScript/CoffeScript/Kotlin/etc sourcemaps
are detailed, AST/PSI-aware (not line by line, but node by node). As result, only GWT
requires some hacks to impement name mappings  (so, support of TypeScript/CoffeScript/Kotlin/etc
is more reliable).

Reported by develar on 2015-01-17 14:42:59

[dankurka]

I have found a similar issue with sourcemaps at work.  We had an off-by-24 error that
was caused by CrossSiteIframeLinker.getModulePrefix.  That method emits (for us) 24
lines of code which is then added to a ScriptFragmentEditsArtifact, which it seems
is supposed to offset the sourcemaps to account for these extra lines.  However, this
artifact is not considered, and the sourcemaps come out a bit wonky.

My workaround (in a custom subclass of CrossSiteIframeLinker): 

  @Override
  protected String getModulePrefix(TreeLogger logger, LinkerContext context, String
strongName)
      throws UnableToCompleteException {
    String original = super.getModulePrefix(logger, context, strongName);
    // The newlines in the module prefix are not correctly adjusted for in the sourcemaps.
    // Replacing the newlines here allows the sourcemaps to line up correctly
    return original.replaceAll("\n", "");
  }

Reported by James@wetheinter.net on 2015-04-09 17:17:29

[dankurka]

Issue 9046 has been merged into this issue.

Reported by t.broyer on 2015-05-24 22:54:25