Add support for transforming Checkstyle XML output to JUnit XML

java/BUILD.bazel

@@ -17,6 +17,7 @@ alias(
 exports_files([
     "checkstyle-strict.xml",
     "google-checks.xml",
+    "checkstyle2junit.xslt",
 ])
 
 checkstyle_config(

java/checkstyle2junit.xslt

@@ -0,0 +1,46 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+  <xsl:output encoding="UTF-8" method="xml"></xsl:output>
+
+  <xsl:template match="/">
+    <testsuites>
+      <testsuite package="Checkstyle">
+        <xsl:attribute name="name">
+          <xsl:value-of select="//checkstyle/file/@name" />
+        </xsl:attribute>
+        <xsl:attribute name="tests">
+          <xsl:value-of select="count(.//error)" />
+        </xsl:attribute>
+        <xsl:attribute name="errors">
+          <xsl:value-of select="count(.//error)" />
+        </xsl:attribute>
+        <xsl:for-each select="//checkstyle">
+          <xsl:apply-templates />
+        </xsl:for-each>
+      </testsuite>
+    </testsuites>
+  </xsl:template>
+
+  <xsl:template match="error">
+    <testcase>
+      <xsl:attribute name="name">
+        <xsl:value-of select="@source" />
+      </xsl:attribute>
+      <xsl:attribute name="classname">
+        <xsl:value-of select="../@name" />
+      </xsl:attribute>
+      <error>
+        <xsl:attribute name="type">
+          <xsl:value-of select="@source" />
+        </xsl:attribute>
+        <xsl:attribute name="message">
+          <xsl:text>Line </xsl:text>
+          <xsl:value-of select="@line" />
+          <xsl:text>: </xsl:text>
+          <xsl:value-of select="@message" />
+        </xsl:attribute>
+      </error>
+    </testcase>
+  </xsl:template>
+
+</xsl:stylesheet>

java/private/checkstyle.bzl

@@ -9,23 +9,30 @@ Checkstyle rule implementation
 def _checkstyle_impl(ctx):
     info = ctx.attr.config[CheckStyleInfo]
     config = info.config_file
-    output_format = info.output_format
 
     config_dir = paths.dirname(config.short_path)
     maybe_cd_config_dir = ["cd {}".format(config_dir)] if config_dir else []
 
     script = "\n".join([
         "#!/usr/bin/env bash",
         "set -o pipefail",
-        "set -e",
+        "set +e",
         "OLDPWD=$PWD",
     ] + maybe_cd_config_dir + [
-        "$OLDPWD/{lib} -f {output_format} -c {config} {srcs} |sed s:$OLDPWD/::g".format(
+        "$OLDPWD/{lib} -o checkstyle.xml -f xml -c {config} {srcs}".format(
             lib = info.checkstyle.short_path,
-            output_format = output_format,
             config = config.basename,
             srcs = " ".join(["$OLDPWD/" + f.short_path for f in ctx.files.srcs]),
         ),
+        "checkstyle_exit_code=$?",
+        # Apply sed to the file in place
+        "sed s:$OLDPWD/::g checkstyle.xml > checkstyle-stripped.xml",
+        # Run the Java XSLT transformation tool
+        "$OLDPWD/{xslt_transformer} checkstyle-stripped.xml $OLDPWD/{xslt} > $XML_OUTPUT_FILE".format(
+            xslt_transformer = ctx.executable._xslt_transformer.short_path,
+            xslt = ctx.file.xslt.short_path,
+        ),
+        "exit $checkstyle_exit_code",
     ])
     out = ctx.actions.declare_file(ctx.label.name + "exec")
 
@@ -35,8 +42,8 @@ def _checkstyle_impl(ctx):
     )
 
     runfiles = ctx.runfiles(
-        files = ctx.files.srcs + [info.checkstyle],
-    )
+        files = ctx.files.srcs + [info.checkstyle, ctx.file.xslt],
+    ).merge(ctx.attr._xslt_transformer[DefaultInfo].default_runfiles)
 
     return [
         DefaultInfo(
@@ -64,10 +71,15 @@ _checkstyle_test = rule(
                 [CheckStyleInfo],
             ],
         ),
-        "output_format": attr.string(
-            doc = "Output Format can be plain or xml. Defaults to plain",
-            values = ["plain", "xml"],
-            default = "plain",
+        "xslt": attr.label(
+            doc = "Path to the checkstyle2junit.xslt file",
+            allow_single_file = True,
+            default = "@contrib_rules_jvm//java:checkstyle2junit.xslt",
+        ),
+        "_xslt_transformer": attr.label(
+            default = "@contrib_rules_jvm//java/src/com/github/bazel_contrib/contrib_rules_jvm/xml:XSLTTransformer",
+            executable = True,
+            cfg = "exec",
         ),
     },
     executable = True,

java/src/com/github/bazel_contrib/contrib_rules_jvm/xml/BUILD.bazel

@@ -0,0 +1,14 @@
+load("@rules_java//java:defs.bzl", "java_binary", "java_library")
+
+java_library(
+    name = "xml",
+    srcs = ["XSLTTransformer.java"],
+    visibility = ["//:__subpackages__"],
+)
+
+java_binary(
+    name = "XSLTTransformer",
+    main_class = "XSLTTransformer",
+    visibility = ["//visibility:public"],
+    runtime_deps = [":xml"],
+)

java/src/com/github/bazel_contrib/contrib_rules_jvm/xml/XSLTTransformer.java

@@ -0,0 +1,35 @@
+import java.io.File;
+import javax.xml.transform.Transformer;
+import javax.xml.transform.TransformerFactory;
+import javax.xml.transform.stream.StreamResult;
+import javax.xml.transform.stream.StreamSource;
+
+public class XSLTTransformer {
+  public static void main(String[] args) throws Exception {
+    if (args.length != 2) {
+      System.err.println("Usage: java XSLTTransformer <input.xml> <transform.xslt>");
+      System.exit(1);
+    }
+
+    String inputXML = args[0];
+    String xsltFile = args[1];
+
+    // Create transformer factory
+    TransformerFactory factory = TransformerFactory.newInstance();
+
+    // Load the XSLT file
+    StreamSource xslt = new StreamSource(new File(xsltFile));
+
+    // Create a transformer
+    Transformer transformer = factory.newTransformer(xslt);
+
+    // Load the input XML file
+    StreamSource xmlInput = new StreamSource(new File(inputXML));
+
+    // Set the output file
+    StreamResult xmlOutput = new StreamResult(System.out);
+
+    // Perform the transformation
+    transformer.transform(xmlInput, xmlOutput);
+  }
+}