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If a shebang already exists when adding a preamble, preserve it. #19133

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merged 1 commit into from May 24, 2023
Merged

If a shebang already exists when adding a preamble, preserve it. #19133

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25 changes: 20 additions & 5 deletions src/python/pants/backend/tools/preamble/rules.py
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Expand Up @@ -23,10 +23,20 @@ class PreambleRequest(FmtFilesRequest):

@memoized
def _template_checker_regex(template: str) -> re.Pattern:
maybe_shebang = r"(#!.*\n)?"
shebang = r"(?P<shebang>#!.*\n)"
if re.match(shebang, template):
# If the template already contains a shebang, don't attempt to match one.
shebang = r"(?P<shebang>)"
maybe_shebang = f"{shebang}?"

subbed = string.Template(template).safe_substitute(year=r"====YEAR====")
raw_regex = re.escape(subbed).replace("====YEAR====", r"\d{4}")
return re.compile(maybe_shebang + raw_regex)
maybe_template = f"(?P<template>{raw_regex})?"

# Wrap in `?s` to enable matching newlines with `.`.
body = "(?s:(?P<body>.*))"

return re.compile(maybe_shebang + maybe_template + body)


@memoized
Expand Down Expand Up @@ -57,10 +67,15 @@ async def preamble_fmt(
for path, template in template_by_path.items():
regex = _template_checker_regex(template)
file_content = contents_by_path[path].content
if not regex.match(file_content.decode("utf-8")):
new_content = _substituted_template(template).encode("utf-8") + file_content
matched = regex.fullmatch(file_content.decode("utf-8"))
# The regex produced by `_template_checker_regex` is infallible.
assert matched
if not matched.group("template"):
shebang = matched.group("shebang")
body = matched.group("body")
new_content = (shebang if shebang else "") + _substituted_template(template) + body
contents_by_path[path] = dataclasses.replace(
contents_by_path[path], content=new_content
contents_by_path[path], content=new_content.encode("utf-8")
)

output_snapshot = await Get(Snapshot, CreateDigest(contents_by_path.values()))
Expand Down
21 changes: 21 additions & 0 deletions src/python/pants/backend/tools/preamble/rules_integration_test.py
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Expand Up @@ -141,6 +141,27 @@ def test_ignores_shebang(rule_runner: RuleRunner) -> None:
assert fmt_result.did_change is False


def test_preserves_shebang(rule_runner: RuleRunner) -> None:
rule_runner.write_files(
{
"foo.py": "#!/usr/bin/env python3\n...",
}
)
fmt_result = run_preamble(
rule_runner,
{
"**/*.py": "# Copyright\n",
},
)

assert fmt_result.did_change is True
assert fmt_result.output == rule_runner.make_snapshot(
{
"foo.py": "#!/usr/bin/env python3\n# Copyright\n...",
}
)


def test_preamble_includes_shebang(rule_runner: RuleRunner) -> None:
files_before = {"foo.py": "#!/usr/bin/env python3\n# Copyright"}

Expand Down