feat(gapic-generator): add CodeWriter pure-python codegen utility

[ohmayr]

No description provided.

[gemini-code-assist]

Code Review

This pull request introduces a new CodeWriter class to generate structured Python code programmatically, replacing Jinja templates, and includes comprehensive unit tests. The review feedback recommends moving the textwrap import to the top of the file to adhere to PEP-8, sorting generated imports within groups (straight imports before from-imports), and updating the corresponding unit tests to match the sorted output.

[gemini-code-assist]

According to PEP-8, imports should be placed at the top of the file rather than inside functions, unless there is a specific reason (such as avoiding circular dependencies or heavy import costs). Since textwrap is a lightweight standard library module, please move import textwrap to the top of the file.

Suggested change

	import textwrap
	cleaned = textwrap.dedent(text).strip("\n")
	cleaned = textwrap.dedent(text).strip("\n")

References

1. Imports are always put at the top of the file, just after any module comments and docstrings, and before module globals and constants. ^(link)

[gemini-code-assist]

The docstring for write_imports claims to emit PEP-8 compliant grouped import statements, but the imports within each group are currently written in insertion order rather than being sorted. To ensure PEP-8 compliance automatically, we should sort the imports within each group (straight imports first, then from-imports, both sorted alphabetically).

Suggested change

	groups = [g for g in (std, third_party, local) if g]
	for i, group in enumerate(groups):
	for item in group:
	if isinstance(item, str):
	self.write_line(
	item if item.startswith("import ") or item.startswith("from ") else f"import {item}"
	)
	elif isinstance(item, tuple):
	module, symbols = item
	sym_str = ", ".join(sorted(symbols))
	self.write_line(f"from {module} import {sym_str}")
	if i < len(groups) - 1:
	self.newline()
	groups = [g for g in (std, third_party, local) if g]
	for i, group in enumerate(groups):
	formatted = []
	for item in group:
	if isinstance(item, str):
	formatted.append(
	item if item.startswith("import ") or item.startswith("from ") else f"import {item}"
	)
	elif isinstance(item, tuple):
	module, symbols = item
	sym_str = ", ".join(sorted(symbols))
	formatted.append(f"from {module} import {sym_str}")
	# Sort imports: straight imports first, then from-imports, both alphabetically
	for stmt in sorted(formatted, key=lambda s: (1, s) if s.startswith("from ") else (0, s)):
	self.write_line(stmt)
	if i < len(groups) - 1:
	self.newline()

References

1. Within each group, imports should be sorted. ^(link)

[gemini-code-assist]

Update the expected imports output to match the new sorted behavior where straight imports are grouped before from-imports and sorted alphabetically.

Suggested change

	expected = (
	"from collections import OrderedDict\n"
	"import json\n"
	"from typing import Callable, Dict, List\n"
	"\n"
	"from google.api_core import gapic_v1\n"
	"\n"
	"from .transports.base import FooTransport\n"
	)
	expected = (
	"import json\n"
	"from collections import OrderedDict\n"
	"from typing import Callable, Dict, List\n"
	"\n"
	"from google.api_core import gapic_v1\n"
	"\n"
	"from .transports.base import FooTransport\n"
	)