turn path/BUILD into path in the tailor goal (pantsbuild#19323)

Transforms a request to `pants tailor /path/to/BUILD` into `pants tailor
/path/to` which is probably what people want.

The wrinkle is that if the BUILD file exists, we need to turn a
FileLiteralSpec into DirLiteralSpec.

closes pantsbuild#17868

src/python/pants/core/goals/tailor.py

@@ -10,9 +10,10 @@
 from abc import ABCMeta
 from collections import defaultdict
 from dataclasses import dataclass
+from pathlib import Path
 from typing import Iterable, Iterator, Mapping, cast
 
-from pants.base.specs import AncestorGlobSpec, RawSpecs, Specs
+from pants.base.specs import AncestorGlobSpec, DirLiteralSpec, RawSpecs, Specs
 from pants.build_graph.address import Address
 from pants.engine.collection import DeduplicatedCollection
 from pants.engine.console import Console
@@ -571,6 +572,48 @@ def make_content(bf_path: str, pts: Iterable[PutativeTarget]) -> FileContent:
     return EditedBuildFiles(new_digest, tuple(sorted(created)), tuple(sorted(updated)))
 
 
+def spec_with_build_to_dir(spec: RawSpecs, build_file_patterns: tuple[str, ...]) -> RawSpecs:
+    """Convert a spec like `path/to/BUILD` into `path/to`, which is probably the intention."""
+
+    filespec_matcher = FilespecMatcher(build_file_patterns, ())
+
+    def is_build_file(s: str):
+        return bool(filespec_matcher.matches([s]))
+
+    new_file_literals = []
+    new_dir_literals = []
+
+    # handles existing BUILD files
+    for file_literal in spec.file_literals:
+        path = Path(file_literal.file)
+        if is_build_file(path.name):
+            # convert FileLiteralSpec into DirLiteralSpec
+            new_dir_literals.append(DirLiteralSpec(path.parent.as_posix()))
+        else:
+            new_file_literals.append(file_literal)
+
+    # If the BUILD file doesn't exist (possibly because it was deleted)
+    # it will appear as a dir_literal
+    for dir_literal in spec.dir_literals:
+        path = Path(dir_literal.directory)
+        if is_build_file(path.name):
+            new_dir_literals.append(DirLiteralSpec(path.parent.as_posix()))
+        else:
+            new_dir_literals.append(dir_literal)
+
+    return dataclasses.replace(
+        spec, dir_literals=tuple(new_dir_literals), file_literals=tuple(new_file_literals)
+    )
+
+
+def resolve_specs_with_build(specs: Specs, build_file_patterns: tuple[str, ...]) -> Specs:
+    """Convert Specs with specs like `path/to/BUILD` into `path/to`, which is probably the
+    intention."""
+    new_includes = spec_with_build_to_dir(specs.includes, build_file_patterns)
+    new_ignores = spec_with_build_to_dir(specs.ignores, build_file_patterns)
+    return dataclasses.replace(specs, includes=new_includes, ignores=new_ignores)
+
+
 @goal_rule
 async def tailor(
     tailor_subsystem: TailorSubsystem,
@@ -581,6 +624,9 @@ async def tailor(
     build_file_options: BuildFileOptions,
 ) -> TailorGoal:
     tailor_subsystem.validate_build_file_name(build_file_options.patterns)
+
+    specs = resolve_specs_with_build(specs, build_file_options.patterns)
+
     if not specs:
         if not specs.includes.from_change_detection:
             logger.warning(
@@ -593,6 +639,7 @@ async def tailor(
                       * `{bin_name()} tailor ::` to run on everything
                       * `{bin_name()} tailor dir::` to run on `dir` and subdirs
                       * `{bin_name()} tailor dir` to run on `dir`
+                      * `{bin_name()} tailor dir/{tailor_subsystem.build_file_name}` to run on `dir`
                       * `{bin_name()} --changed-since=HEAD tailor` to only run on changed and new files
                     """
                 )

src/python/pants/core/goals/tailor_test.py

@@ -10,6 +10,7 @@
 
 import pytest
 
+from pants.base.specs import DirGlobSpec, DirLiteralSpec, FileLiteralSpec, RawSpecs, Specs
 from pants.core.goals import tailor
 from pants.core.goals.tailor import (
     AllOwnedSources,
@@ -25,6 +26,7 @@
     default_sources_for_target_type,
     has_source_or_sources_field,
     make_content_str,
+    resolve_specs_with_build,
 )
 from pants.core.util_rules import source_files
 from pants.engine.fs import DigestContents, FileContent, PathGlobs, Paths
@@ -586,3 +588,44 @@ def make_ptgt(path: str, name: str) -> PutativeTarget:
         ),
     )
     assert set(result) == set(valid_ptgts)
+
+
+@pytest.mark.parametrize("build_file_name", ["BUILD", "OTHER_NAME"])
+def test_resolve_specs_targetting_build_files(build_file_name) -> None:
+    specs = Specs(
+        includes=RawSpecs(
+            description_of_origin="CLI arguments",
+            dir_literals=(DirLiteralSpec(f"src/{build_file_name}"), DirLiteralSpec("src/dir")),
+            dir_globs=(DirGlobSpec("src/other/"),),
+            file_literals=(FileLiteralSpec(f"src/exists/{build_file_name}.suffix"),),
+        ),
+        ignores=RawSpecs(
+            description_of_origin="CLI arguments",
+            dir_literals=(DirLiteralSpec(f"bad/{build_file_name}"), DirLiteralSpec("bad/dir")),
+            dir_globs=(DirGlobSpec("bad/other/"),),
+            file_literals=(FileLiteralSpec(f"bad/exists/{build_file_name}.suffix"),),
+        ),
+    )
+    build_file_patterns = (build_file_name, f"{build_file_name}.*")
+    resolved = resolve_specs_with_build(specs, build_file_patterns)
+
+    assert resolved.includes.file_literals == tuple()
+    assert resolved.ignores.file_literals == tuple()
+
+    assert resolved.includes.dir_literals == (
+        DirLiteralSpec("src/exists"),
+        DirLiteralSpec("src"),
+        DirLiteralSpec("src/dir"),
+    )
+    assert resolved.ignores.dir_literals == (
+        DirLiteralSpec("bad/exists"),
+        DirLiteralSpec("bad"),
+        DirLiteralSpec("bad/dir"),
+    )
+
+    assert resolved.includes.dir_globs == (
+        DirGlobSpec("src/other/"),
+    ), "did not passthrough other spec type"
+    assert resolved.ignores.dir_globs == (
+        DirGlobSpec("bad/other/"),
+    ), "did not passthrough other spec type"