Meson build writes to the source directory (issue #3507 )

[aneejit1]

The meson build is writing files into the source directory which causes a build failure if the source is read-only. The Python scripts "src/gen-hb-version.py" and "src/gen-harfbuzzcc.py" have been amended so a copy back to the source tree is only performed if the generated files differ from the baselined files (this should therefore only happen when something does
actually change as part of the development process).

[khaledhosny]

As you can see, this copying is intentional and we depend on it. Basically, we want to be able to build HarfBuzz from git checkout without using the build system at all, and some large HarfBuzz consumers depend on this.

[khaledhosny]

What we can do is to check that the files are the same and skip the copying since the copying is only needed when one modifies HarfBuzz source.

[aneejit1]

OK, maybe I'm overthinking this but, would this do? (it's lost the formatting)

# copy it also to the source tree, but only if it has changed
with open(os.path.join (CURRENT_SOURCE_DIR, os.path.basename (OUTPUT)), "r", encoding='utf-8') as baseline:
        fromlines = baseline.readlines()
with open(OUTPUT) as generated:
        tolines = generated.readlines()

diff = difflib.unified_diff(fromlines, tolines)
if next(diff, None) is not None:
        shutil.copyfile (OUTPUT, os.path.join (CURRENT_SOURCE_DIR, os.path.basename (OUTPUT)))

[khaledhosny]

baseline.read() != generated.read() should be enough.

[aneejit1]

Hmm! Well the checks seem to be a bit happier about that.

[khaledhosny]

Please squash all the commits into one, thanks.

[behdad]

Please squash all the commits into one, thanks.

Github merge can do that.