1426269 - Strip comments out of default prefs files

Status: RESOLVED FIXED

(Core :: Preferences: Backend, enhancement)

Description

[Nicholas Nethercote [inactive]]

On my Linux64 machine greprefs.js is about 220KB. With the comments stripped out, it's slightly less than half of that. We preprocess these files with preprocessor.py anyway, so when we do that we should strip out comments. This will reduce the size of the omnijar and reduce file loading & parsing time at process (chrome and content) startup.

Comment 1

[Nicholas Nethercote [inactive]]

Attachment: Bug 1426269 - Remove the `spaces` filter from preprocessor.py. r=glandium

It's not used, probably because it's pretty strange and hard to imagine using
safely. (Stripping leading and trailing space could be useful, but collapsing
sequences of spaces? Hmm.)

Comment 2

[Nicholas Nethercote [inactive]]

Attachment: Bug 1426269 - Change the `slashslash` filter in preprocessor.py. r=glandium

This commit does the following.

• Renames slashslash as dumbComments. As a result, it now comes before
  emptyLines in alphabetical ordering, which means that if you apply both
  dumbComments and emptyLines, lines that contain only comments will be
  fully removed.

  (I contemplated changing the filter ordering to match the order specified,
  rather than using alphabetical ordering, but that was more invasive and not
  obviously better.)

• Changes dumbComments so it only applies if the comment is at the start of
  the line (with optional leading whitespace). This is so it can be used with
  prefs files, which contain lines like pref("foo", "https://mozilla.org");
  where the // must not be treated as a comment.

Note that slashslash wasn't being used anywhere.

Depends on D88240

Comment 3

[Nicholas Nethercote [inactive]]

Attachment: Bug 1426269 - Filter full-line comments and empty lines from prefs files. r=glandium

For a local build on my Linux64 box, this reduces greprefs.js from 174,906
bytes to 103,221 bytes, and firefox.js from 112,100 bytes to 68,656 bytes.

Depends on D88242

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/76efaf59feb8
Remove the `spaces` filter from preprocessor.py. r=glandium
https://hg.mozilla.org/integration/autoland/rev/bcc9e11ca06b
Change the `slashslash` filter in preprocessor.py. r=glandium
https://hg.mozilla.org/integration/autoland/rev/328067bcffe8
Filter full-line comments and empty lines from prefs files. r=glandium,geckoview-reviewers,snorp

Comment 5

[Dorel Luca [:dluca]]

https://hg.mozilla.org/mozilla-central/rev/76efaf59feb8
https://hg.mozilla.org/mozilla-central/rev/bcc9e11ca06b
https://hg.mozilla.org/mozilla-central/rev/328067bcffe8