On Feb 5, 2013, at 6:09 AM, Mark Mentovai <m...@chromium.org> wrote:
> The parser (and the grammar) works the way it does because it’s just
> Python—the whole thing can be slurped in quickly by the interpreter and made
> available to GYP as data. It’s faster than a parser written in Python for a
> similar language would be, and it’d likely take a binary Python module to
> approach or exceed this speed. Developers don’t like waiting for tools.
Is that a result based on testing, or just a projectiom? My guess would be that
most incremental builds do not add or remove any files, and therefore do not
need to regenerate the project files at all, so the speed of parsing GYP files
is unlikely to have a major impact, unless it's a truly massive difference.
I have to say that the syntax weight of gyp files (quotes, commas, braces,
brackets) makes them feel harder to read and edit than other build file formats
designed for human consumption (obviously Xcode is worse).
Compare this bit of gyp for generating a derived source file:
>> {
>> 'action_name': 'XMLNames',
>> 'inputs': [
>> '../dom/make_names.pl',
>> '../xml/xmlattrs.in',
>> ],
>> 'outputs': [
>> '<(SHARED_INTERMEDIATE_DIR)/webkit/XMLNames.cpp',
>> '<(SHARED_INTERMEDIATE_DIR)/webkit/XMLNames.h',
>> ],
>> 'action': [
>> 'python',
>> 'scripts/action_makenames.py',
>> '<@(_outputs)',
>> '--',
>> '<@(_inputs)',
>> '--',
>> '--extraDefines', '<(feature_defines)'
>> ],
>> 'msvs_cygwin_shell': 1,
>> },
vs the equivalent bit of DerivedSources.make:
>> XMLNames.cpp : dom/make_names.pl xml/xmlattrs.in
>> perl -I $(WebCore)/bindings/scripts $< --attrs
>> $(WebCore)/xml/xmlattrs.in
Or GNUMakefile.am:
>> DerivedSources/WebCore/XMLNames.cpp DerivedSources/WebCore/XMLNames.h:
>> $(WebCore)/dom/make_names.pl $(WebCore)/xml/xmlattrs.in
>> $(AM_V_GEN)$(PERL) -I$(WebCore)/bindings/scripts $< --attrs
>> $(WebCore)/xml/xmlattrs.in --outputDir "$(GENSOURCES_WEBCORE)"
Or DerivedSources.pri:
>> xmlnames.output = XMLNames.cpp
>> xmlnames.input = XML_NAMES
>> xmlnames.script = $$PWD/dom/make_names.pl
>> xmlnames.commands = perl -I$$PWD/bindings/scripts $$xmlnames.script --attrs
>> $$PWD/xml/xmlattrs.in --preprocessor \"$${QMAKE_MOC} -E\" --outputDir
>> ${QMAKE_FUNC_FILE_OUT_PATH}
>> GENERATORS += xmlnames
Gyp kind of seems like an outlier in heaviness of the syntax compared to the
other build systems.The irony is that Python itself doesn't use a lot of
punctuation in its syntax, so actual Python code looks much cleaner. I like to
read Python code, but I can't say I enjoy reading the Gyp syntax. This makes me
wonder if a Python DSL might be more legible than simply using a dictionary.
Alternately, maybe it turns out that parsing a custom language is not that huge
a hit in practice.
Regards,
Maciej
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