Work around JDT absolute path issue. (#14)

This is a simple attempt to make paths in the output of the JDT compiler
relative again. Somehow they end up becoming absolute, which breaks IDEs
decided to rely on compiler output parsing for error reporting.

eclipse-jdt/eclipse.jdt.core#1061

Author: guw

.bazelproject

@@ -0,0 +1,13 @@
+# The project view file (.bazelproject) is used to import targets into the IDE.
+#
+# See: https://ij.bazel.build/docs/project-views.html
+#
+# This files provides a default experience for developers working with the project
+
+
+directories:
+  .
+
+derive_targets_from_directories: true
+
+java_language_level: 11

.gitignore

@@ -11,6 +11,7 @@ bazel-*
 .project
 .settings/
 .classpath
+.eclipse
 
 # output folders
 bin/

WORKSPACE

@@ -70,6 +70,8 @@ jvm_maven_import_external(
     name = "rules_jdt_guava",
     artifact = "com.google.guava:guava:31.0.1-jre",
     artifact_sha256 = "d5be94d65e87bd219fb3193ad1517baa55a3b88fc91d21cf735826ab5af087b9",
+    srcjar_urls = [server + "/com/google/guava/guava/31.0.1-jre/guava-31.0.1-jre-sources.jar" for server in _DEFAULT_REPOSITORIES],
+    srcjar_sha256 = "fc0fb66f315f10b8713fc43354936d3649a8ad63f789d42fd7c3e55ecf72e092",
     licenses = ["notice"],
     server_urls = _DEFAULT_REPOSITORIES,
 )

compiler/src/main/buildjar/com/google/devtools/build/buildjar/javac/BlazeEcjMain.java

@@ -20,6 +20,7 @@
 import static java.nio.charset.StandardCharsets.UTF_8;
 import static java.util.Comparator.comparing;
 
+import java.io.File;
 import java.io.IOError;
 import java.io.IOException;
 import java.io.PrintWriter;
@@ -131,6 +132,7 @@ public static BlazeJavacResult compile(BlazeJavacArguments arguments) {
 //        }
 //      }
     }
+    
     errWriter.flush();
     ImmutableList<FormattedDiagnostic> diagnostics = diagnosticsBuilder.build();
 
@@ -151,15 +153,56 @@ public static BlazeJavacResult compile(BlazeJavacArguments arguments) {
         }
       }
     }
+    
+    String output = errOutput.toString();
 
-    return BlazeJavacResult.createFullResult(
+    // JDT uses getAbsolutePath, which makes reporting of file paths to point into Bazel sandbox
+    // this causes issues in IntelliJ 
+    String canonicalPathPrefix = null;
+    try {
+		canonicalPathPrefix = detectWorkingDirPathPrefix(arguments);
+		if(canonicalPathPrefix != null) {
+			output = output.replace(canonicalPathPrefix, "");
+		}
+    } catch (IOException e) {
+		e.printStackTrace(errWriter);
+	    errWriter.flush();
+	}
+
+	return BlazeJavacResult.createFullResult(
         status,
         filterDiagnostics(werror, diagnostics),
-        errOutput.toString(),
+        output,
         compiler,
         builder.build());
   }
 
+	private static String detectWorkingDirPathPrefix(BlazeJavacArguments arguments) throws IOException {
+		// since the JDT compiler is executed from within the sandbox, the absolute path will be resolved to the working directory
+		// we simple remove the working directory
+		String workDir = System.getProperty("user.dir");
+		if(workDir == null)
+			throw new IOException("No working directory returned by JVM for property user.dir!");
+		
+		if(!workDir.endsWith("/")) {
+			workDir += "/";
+		}
+
+		// the following code is only for our own sanity
+		Optional<Path> first = arguments.sourcePath().stream().findFirst();
+		if (!first.isPresent()) {
+			first = arguments.sourceFiles().stream().findFirst();
+		}
+
+		String absoluteFilePath = first.get().toAbsolutePath().toString();
+		if (!absoluteFilePath.startsWith(workDir)) {
+			String filePath = first.get().toString();
+			throw new IOException(String.format("Unable to confirm working dir '%s' using file '%s' with absolute path '%s'!", workDir, filePath, absoluteFilePath));
+		}
+
+		return workDir;
+	}
+
   private static Status fromResult(Boolean result) {
 	if(result == null)
 		return Status.CRASH;