scala: add scalafmt support for fmt and lint goals (pantsbuild#…

…13814)

Add the `scalafmt` tool for `fmt` and `lint` goals.

Pants will choose the nearest ancestor `.scalafmt.conf` file as the configuration file to use for a source file. This differs from the logic used by `scalafmt` which only chooses between a `.scalafmt.conf` in the same directory as a file or one in the root of the repository. This should provide a better experience for multi-team monorepos where it could be useful to have a `.scalafmt.conf` that applies to a subtree of the repository.

Closes pantsbuild#11943.

pants.toml

@@ -23,6 +23,7 @@ backend_packages.add = [
   "pants.backend.experimental.java.debug_goals",
   "pants.backend.experimental.python",
   "pants.backend.experimental.scala",
+  "pants.backend.experimental.scala.lint.scalafmt",
   "pants.backend.experimental.scala.debug_goals",
   "internal_plugins.releases",
 ]
@@ -179,6 +180,9 @@ lockfile = "src/python/pants/backend/java/test/junit.default.lockfile.txt"
 [google-java-format]
 lockfile = "src/python/pants/backend/java/lint/google_java_format/google_java_format.default.lockfile.txt"
 
+[scalafmt]
+lockfile = "src/python/pants/backend/scala/lint/scalafmt/scalafmt.default.lockfile.txt"
+
 [toolchain-setup]
 repo = "pants"
 

src/python/pants/backend/experimental/scala/lint/scalafmt/BUILD

@@ -0,0 +1,4 @@
+# Copyright 2021 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+python_sources()

src/python/pants/backend/experimental/scala/lint/scalafmt/register.py

@@ -0,0 +1,15 @@
+# Copyright 2021 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+from pants.backend.experimental.scala.register import rules as all_scala_rules
+from pants.backend.scala.lint import scala_lang_fmt
+from pants.backend.scala.lint.scalafmt import rules as scalafmt_rules
+from pants.backend.scala.lint.scalafmt import skip_field
+
+
+def rules():
+    return [
+        *all_scala_rules(),
+        *scala_lang_fmt.rules(),
+        *scalafmt_rules.rules(),
+        *skip_field.rules(),
+    ]

src/python/pants/backend/java/lint/google_java_format/rules.py

@@ -96,15 +96,11 @@ async def setup_google_java_format(
             "--add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED",
         ]
 
-    maybe_aosp_option = []
-    if tool.aosp:
-        maybe_aosp_option = ["--aosp"]
-
     args = [
         *jdk_setup.args(bash, tool_classpath.classpath_entries()),
         *maybe_java16_or_higher_options,
         "com.google.googlejavaformat.java.Main",
-        *maybe_aosp_option,
+        *(["--aosp"] if tool.aosp else []),
         "--dry-run" if setup_request.check_only else "--replace",
         *source_files.files,
     ]

src/python/pants/backend/scala/dependency_inference/BUILD

@@ -10,4 +10,6 @@ python_tests(name="tests", timeout=240)
 scala_sources(
     name="scala_parser",
     compatible_resolves=["scala_parser"],
+    # TODO: Allow the parser files to be formatted.
+    skip_scalafmt=True,
 )

src/python/pants/backend/scala/lint/BUILD

@@ -0,0 +1,4 @@
+# Copyright 2021 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+python_sources()

src/python/pants/backend/scala/lint/scala_lang_fmt.py

@@ -0,0 +1,61 @@
+# Copyright 2021 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+from dataclasses import dataclass
+from typing import Iterable
+
+from pants.backend.scala.target_types import ScalaSourceField
+from pants.core.goals.fmt import FmtResult, LanguageFmtResults, LanguageFmtTargets
+from pants.core.goals.style_request import StyleRequest
+from pants.core.util_rules.source_files import SourceFiles, SourceFilesRequest
+from pants.engine.fs import Digest, Snapshot
+from pants.engine.internals.selectors import Get
+from pants.engine.rules import collect_rules, rule
+from pants.engine.unions import UnionMembership, UnionRule, union
+
+
+@dataclass(frozen=True)
+class ScalaLangFmtTargets(LanguageFmtTargets):
+    required_fields = (ScalaSourceField,)
+
+
+@union
+class ScalaLangFmtRequest(StyleRequest):
+    pass
+
+
+@rule
+async def format_scala_target(
+    scala_fmt_targets: ScalaLangFmtTargets, union_membership: UnionMembership
+) -> LanguageFmtResults:
+    original_sources = await Get(
+        SourceFiles,
+        SourceFilesRequest(target[ScalaSourceField] for target in scala_fmt_targets.targets),
+    )
+    prior_formatter_result = original_sources.snapshot
+
+    results = []
+    fmt_request_types: Iterable[type[StyleRequest]] = union_membership[ScalaLangFmtRequest]
+    for fmt_request_type in fmt_request_types:
+        request = fmt_request_type(
+            (
+                fmt_request_type.field_set_type.create(target)
+                for target in scala_fmt_targets.targets
+                if fmt_request_type.field_set_type.is_applicable(target)
+            ),
+            prior_formatter_result=prior_formatter_result,
+        )
+        if not request.field_sets:
+            continue
+        result = await Get(FmtResult, ScalaLangFmtRequest, request)
+        results.append(result)
+        if result.did_change:
+            prior_formatter_result = await Get(Snapshot, Digest, result.output)
+    return LanguageFmtResults(
+        tuple(results),
+        input=original_sources.snapshot.digest,
+        output=prior_formatter_result.digest,
+    )
+
+
+def rules():
+    return [*collect_rules(), UnionRule(LanguageFmtTargets, ScalaLangFmtTargets)]

src/python/pants/backend/scala/lint/scalafmt/BUILD

@@ -0,0 +1,8 @@
+# Copyright 2021 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+python_sources(dependencies=[":lockfile"])
+
+python_tests(name="tests", timeout=360)
+
+resource(name="lockfile", source="scalafmt.default.lockfile.txt")