Support multiple configuration files for different modules in checkstyle

example/BUILD.bazel

@@ -17,6 +17,7 @@ exports_files(
         ".flake8",
         "pmd.xml",
         "checkstyle.xml",
+        "checkstyle_subdir.xml",
         "checkstyle-suppressions.xml",
         ".ruff.toml",
         ".shellcheckrc",

example/checkstyle_subdir.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0"?>
+<!DOCTYPE module PUBLIC
+          "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
+          "https://checkstyle.org/dtds/configuration_1_3.dtd">
+<module name="Checker">
+
+  <module name="TreeWalker">
+    <module name="UnusedImports"/>
+  </module>
+
+  <module name="LineLength">
+    <property name="max" value="84"/>
+  </module>
+
+  <module name="SuppressionFilter">
+    <property name="file" value="checkstyle-suppressions.xml"/>
+  </module>
+
+</module>

example/src/subdir/BUILD.bazel

@@ -24,3 +24,8 @@ ts_project(
         "//:node_modules/moment",
     ],
 )
+
+java_library(
+    name = "bar",
+    srcs = ["Bar.java"],
+)

example/src/subdir/Bar.java

@@ -0,0 +1,10 @@
+package src.subdir;
+
+// Unused imports are suppressed in suppressions.xml, so this should not raise issue.
+import java.util.Objects;
+import java.io.BufferedInputStream;
+
+public class Bar {
+  // Max line length set to 20, so this should raise issue.
+  protected void finalize(int a) {}
+}

example/tools/lint/linters.bzl

@@ -52,9 +52,13 @@ pmd = lint_pmd_aspect(
 pmd_test = lint_test(aspect = pmd)
 
 checkstyle = lint_checkstyle_aspect(
-    binary = Label("@//tools/lint:checkstyle"),
-    config = Label("@//:checkstyle.xml"),
-    data = [Label("@//:checkstyle-suppressions.xml")],
+    binary = "@@//tools/lint:checkstyle",
+    config = "@@//:checkstyle.xml",
+    configs = {
+        "@@//:checkstyle.xml": "@@//src,@@//test",
+        "@@//:checkstyle_subdir.xml": "@@//src/subdir",
+    },
+    data = ["@@//:checkstyle-suppressions.xml"],
 )
 
 checkstyle_test = lint_test(aspect = checkstyle)

lint/checkstyle.bzl

@@ -32,6 +32,13 @@ load("//lint/private:lint_aspect.bzl", "LintOptionsInfo", "filter_srcs", "noop_l
 
 _MNEMONIC = "AspectRulesLintCheckstyle"
 
+def rebuild_map(configs):
+    directory_to_config = {}
+    for config, directories in configs.items():
+        for directory in directories.split(","):
+            directory_to_config[directory] = config
+    return directory_to_config
+
 def checkstyle_action(ctx, executable, srcs, config, data, stdout, exit_code = None, options = []):
     """Run Checkstyle as an action under Bazel.
 
@@ -42,6 +49,7 @@ def checkstyle_action(ctx, executable, srcs, config, data, stdout, exit_code = N
         executable: label of the the Checkstyle program
         srcs: java files to be linted
         config: label of the checkstyle.xml file
+        configs: dictionary mapping package label to their respective checkstyle.xml file
         data: labels of additional xml files such as suppressions.xml
         stdout: output file to generate
         exit_code: output file to write the exit code.
@@ -82,6 +90,17 @@ def _checkstyle_aspect_impl(target, ctx):
         return []
 
     files_to_lint = filter_srcs(ctx.rule)
+    config_file = ctx.file._config
+    config_maps = rebuild_map(ctx.attr._configs)
+    if ctx.attr._configs:
+        label = str(target.label)
+        keys = sorted(config_maps.keys(), key=len, reverse = True)
+        for key in keys:
+            if label.startswith(key):
+                config = config_maps[key]
+                config_file = config.files.to_list()[0]
+                break
+
     outputs, info = output_files(_MNEMONIC, target, ctx)
     if len(files_to_lint) == 0:
         noop_lint_action(ctx, outputs)
@@ -91,7 +110,7 @@ def _checkstyle_aspect_impl(target, ctx):
         ctx,
         ctx.executable._checkstyle,
         files_to_lint,
-        ctx.file._config,
+        config_file,
         ctx.files._data,
         outputs.human.out,
         outputs.human.exit_code,
@@ -101,15 +120,15 @@ def _checkstyle_aspect_impl(target, ctx):
         ctx,
         ctx.executable._checkstyle,
         files_to_lint,
-        ctx.file._config,
+        config_file,
         ctx.files._data,
         outputs.machine.out,
         outputs.machine.exit_code,
         ["-f", "sarif"],
     )
     return [info]
 
-def lint_checkstyle_aspect(binary, config, data = [], rule_kinds = ["java_binary", "java_library"]):
+def lint_checkstyle_aspect(binary, config, configs = {}, data = [], rule_kinds = ["java_binary", "java_library"]):
     """A factory function to create a linter aspect.
 
     Attrs:
@@ -147,6 +166,12 @@ def lint_checkstyle_aspect(binary, config, data = [], rule_kinds = ["java_binary
                 doc = "Config file",
                 default = config,
             ),
+            "_configs": attr.label_keyed_string_dict(
+                allow_empty = True,
+                allow_files = True,
+                doc = "Package and configuration files dictionary",
+                default = configs,
+            ),
             "_data": attr.label_list(
                 doc = "Additional files to make available to Checkstyle such as any included XML files",
                 allow_files = True,