Implement tailor goal for Helm charts (pantsbuild#15191)

Implementation of the `tailor` goal based on finding `PutativeTargets` by searching for the Helm chart metadata file.

src/python/pants/backend/experimental/helm/register.py

@@ -1,7 +1,7 @@
 # Copyright 2022 Pants project contributors (see CONTRIBUTORS.md).
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
-from pants.backend.helm.goals import lint, package, publish
+from pants.backend.helm.goals import lint, package, publish, tailor
 from pants.backend.helm.target_types import (
     HelmArtifactTarget,
     HelmChartTarget,
@@ -28,6 +28,7 @@ def rules():
         *lint.rules(),
         *package.rules(),
         *publish.rules(),
+        *tailor.rules(),
         *test_rules(),
         *sources.rules(),
         *tool.rules(),

src/python/pants/backend/helm/goals/tailor.py

@@ -0,0 +1,56 @@
+# Copyright 2022 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+from __future__ import annotations
+
+import os
+from dataclasses import dataclass
+from itertools import chain
+
+from pants.backend.helm.target_types import HelmChartTarget
+from pants.backend.helm.util_rules.chart_metadata import HELM_CHART_METADATA_FILENAMES
+from pants.core.goals.tailor import (
+    AllOwnedSources,
+    PutativeTarget,
+    PutativeTargets,
+    PutativeTargetsRequest,
+)
+from pants.engine.fs import PathGlobs, Paths
+from pants.engine.rules import Get, MultiGet, collect_rules, rule
+from pants.engine.unions import UnionRule
+from pants.util.logging import LogLevel
+
+
+@dataclass(frozen=True)
+class PutativeHelmChartTargetsRequest(PutativeTargetsRequest):
+    pass
+
+
+@rule(desc="Determine candidate Helm chart targets to create", level=LogLevel.DEBUG)
+async def find_putative_helm_targets(
+    request: PutativeHelmChartTargetsRequest, all_owned_sources: AllOwnedSources
+) -> PutativeTargets:
+    found_chart_paths = await MultiGet(
+        Get(Paths, PathGlobs, request.search_paths.path_globs(filename))
+        for filename in HELM_CHART_METADATA_FILENAMES
+    )
+    all_chart_files = chain.from_iterable([p.files for p in found_chart_paths])
+    unowned_chart_files = set(all_chart_files) - set(all_owned_sources)
+
+    putative_targets = []
+    for chart_file in sorted(unowned_chart_files):
+        dirname, filename = os.path.split(chart_file)
+        putative_targets.append(
+            PutativeTarget.for_target_type(
+                HelmChartTarget,
+                name=os.path.basename(dirname),
+                path=dirname,
+                triggering_sources=[filename],
+            )
+        )
+
+    return PutativeTargets(putative_targets)
+
+
+def rules():
+    return [*collect_rules(), UnionRule(PutativeTargetsRequest, PutativeHelmChartTargetsRequest)]

src/python/pants/backend/helm/goals/tailor_test.py

@@ -0,0 +1,55 @@
+# Copyright 2021 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+import os
+
+import pytest
+
+from pants.backend.helm.goals.tailor import PutativeHelmChartTargetsRequest
+from pants.backend.helm.goals.tailor import rules as helm_tailor_rules
+from pants.backend.helm.target_types import HelmChartTarget
+from pants.core.goals.tailor import (
+    AllOwnedSources,
+    PutativeTarget,
+    PutativeTargets,
+    PutativeTargetsSearchPaths,
+)
+from pants.engine.rules import QueryRule
+from pants.testutil.rule_runner import RuleRunner
+
+
+@pytest.fixture
+def rule_runner() -> RuleRunner:
+    return RuleRunner(
+        target_types=[HelmChartTarget],
+        rules=[
+            *helm_tailor_rules(),
+            QueryRule(PutativeTargets, (PutativeHelmChartTargetsRequest, AllOwnedSources)),
+        ],
+    )
+
+
+def test_find_helm_charts(rule_runner: RuleRunner) -> None:
+    rule_runner.write_files(
+        {"src/owned/Chart.yaml": "", "src/foo/Chart.yaml": "", "src/bar/Chart.yml": ""}
+    )
+
+    putative_targets = rule_runner.request(
+        PutativeTargets,
+        [
+            PutativeHelmChartTargetsRequest(PutativeTargetsSearchPaths(("src/",))),
+            AllOwnedSources(["src/owned/Chart.yaml"]),
+        ],
+    )
+
+    def expected_target(path: str, triggering_source: str) -> PutativeTarget:
+        return PutativeTarget.for_target_type(
+            HelmChartTarget,
+            name=os.path.basename(path),
+            path=path,
+            triggering_sources=[triggering_source],
+        )
+
+    assert putative_targets == PutativeTargets(
+        [expected_target("src/foo", "Chart.yaml"), expected_target("src/bar", "Chart.yml")]
+    )