Web Inspector: CodeMirror converts tabs to 4 spaces, messes up indentation on save

[Nikita Vasilyev]

Created attachment 270338 [details]
[Animated GIF] Bug

See the attached GIF.

Steps:
1. Open http://nv.github.io/webkit-inspector-bugs/css-saving-indentation/
2. Open style.css in Resources

Expected:
Tab characters that are used for indentation are preserved as tabs.

Actual:
Tab characters were replaced with four spaces.
As a result of that, editing CSS messes up with indentation.

[Radar WebKit Bug Importer]

<rdar://problem/24428409>

[Nikita Vasilyev]

This should have tests, I don't see any in LayoutTests/inspector/css.

[Devin Rousso]

I tried messing around with changing the default keymap of "Enter" to be something like:

"Enter": (codeMirror) => {
    let doc = codeMirror.getDoc();
    doc.replaceRange("\n", doc.getCursor());
    codeMirror.indentLine(doc.getCursor().line, "prev");
}

This will create the newline at the expected place, but it doesn't seem to want to indent it based on the previous line.  Another "hacky" option would be to toggle `indentWithTabs` based on the number of tab characters in the editor:

let tabs = codeMirror.getValue().match(/\n\t+/g);
codeMirror.setOption("indentWithTabs", tabs && tabs.length >= codeMirror.lineCount() / 2);

I think the first option is better, but it also isn't perfect as it bases the indentation solely on the previous line, meaning that if a single line uses tabs instead of spaces, all newlines off of that line will have tabs too.

[Nikita Vasilyev]

The actual problem here is:
Web Inspector: Minification detection produces false positives for small resources
https://bugs.webkit.org/show_bug.cgi?id=161159

In the animated GIF you can see that pretty printing is on, even though it shouldn't be enabled by default. When it's on, tabs are replaced by 4 spaces.

When pretty printing is off, tab characters get preserved as expected.

*** This bug has been marked as a duplicate of bug 161159 ***