PCBuild needs an analog of make regen-cases

[arhadthedev]

Feature or enhancement

Windows developers need a way to invoke Tools/cases_generator/generate_cases.py with all necessary flags (and, probably, environment variables) skipping the challenge of manual typing.

On non-Windows platforms it's achieved with make regen-all that depends on the regen-cases target:

cpython/Makefile.pre.in

Lines 1490 to 1503 in a679c3d

	regen-cases:
	# Regenerate Python/generated_cases.c.h
	# and Python/opcode_metadata.h
	# from Python/bytecodes.c
	# using Tools/cases_generator/generate_cases.py
	PYTHONPATH=$(srcdir)/Tools/cases_generator \
	$(PYTHON_FOR_REGEN) \
	$(srcdir)/Tools/cases_generator/generate_cases.py \
	--emit-line-directives \
	-o $(srcdir)/Python/generated_cases.c.h.new \
	-m $(srcdir)/Python/opcode_metadata.h.new \
	$(srcdir)/Python/bytecodes.c
	$(UPDATE_FILE) $(srcdir)/Python/generated_cases.c.h $(srcdir)/Python/generated_cases.c.h.new
	$(UPDATE_FILE) $(srcdir)/Python/opcode_metadata.h $(srcdir)/Python/opcode_metadata.h.new

By analogy, PCBuild\regen.targets could do the same for MSBuild.

Pitch

When I tried to resolve a Python/generated_cases.c.h conflict in gh-103976, I found out that I cannot do it easily. An attempt to port the regen-cases target was unsuccessfull:

D:\Oleg\cpython>set PYTHONPATH=D:\Oleg\cpython\Tools\cases_generator

D:\Oleg\cpython>python Tools/cases_generator/generate_cases.py --emit-line-directives Python/generated_cases.c.h.new Python/opcode_metadata.h.new
Running Release|x64 interpreter...
Traceback (most recent call last):
  File "D:\Oleg\cpython\Tools\cases_generator\generate_cases.py", line 1259, in 
    main()
  File "D:\Oleg\cpython\Tools\cases_generator\generate_cases.py", line 1250, in main
    a.parse()  # Raises SyntaxError on failure
    ^^^^^^^^^
  File "D:\Oleg\cpython\Tools\cases_generator\generate_cases.py", line 557, in parse
    self.parse_file(filename, instrs_idx)
  File "D:\Oleg\cpython\Tools\cases_generator\generate_cases.py", line 568, in parse_file
    with open(filename) as file:
         ^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: 'Python/generated_cases.c.h.new'

D:\Oleg\cpython>python Tools/cases_generator/generate_cases.py --emit-line-directives Python/generated_cases.c.h Python/opcode_metadata.h
Running Release|x64 interpreter...
Traceback (most recent call last):
  File "D:\Oleg\cpython\Tools\cases_generator\generate_cases.py", line 1259, in 
    main()
  File "D:\Oleg\cpython\Tools\cases_generator\generate_cases.py", line 1250, in main
    a.parse()  # Raises SyntaxError on failure
    ^^^^^^^^^
  File "D:\Oleg\cpython\Tools\cases_generator\generate_cases.py", line 557, in parse
    self.parse_file(filename, instrs_idx)
  File "D:\Oleg\cpython\Tools\cases_generator\generate_cases.py", line 583, in parse_file
    raise psr.make_syntax_error(
  File "Python/generated_cases.c.h", line 4658
    }
    ^
SyntaxError: Couldn't find '// BEGIN BYTECODES //' in Python/generated_cases.c.h

Autogenegeration would lift off a need to write a private batch-file, debug it, and use it each time Python/bytecodes.c is touched.

Your environment

• CPython versions tested on: Python 3.12.0a7+ (heads/main:5078eedc5b, May 1 2023, 23:20:56) [MSC v.1929 64 bit (AMD64)] on win32

[Fidget-Spinner]

For anyone working around this: I've always let the cases generator use its defaults (which will generate the CPython cases and opcode metadata). py -3.11 Tools/cases_generator/generate_cases.py --emit-line-directives is sufficient.

The extra arguments for files are for forks of CPython (IIRC, Cinder is planning to use it).