bugfix: Fix showing Scala 3 diagnostics

server/src/main/kotlin/org/jetbrains/bsp/bazel/server/diagnostics/BazelRootMessageParser.kt

@@ -56,5 +56,5 @@ object BazelRootMessageParser : Parser {
   }
 
   private fun collectCompilerDiagnostics(output: Output) =
-      generateSequence { CompilerDiagnosticParser.tryParseOne(output) }.toList()
+      generateSequence { CompilerDiagnosticParser.tryParseOne(output) ?: Scala3CompilerDiagnosticParser.tryParseOne(output) }.toList()
 }

server/src/main/kotlin/org/jetbrains/bsp/bazel/server/diagnostics/DiagnosticsParser.kt

@@ -51,6 +51,7 @@ class DiagnosticsParser {
     private val Parsers = listOf(
         BazelRootMessageParser,
         CompilerDiagnosticParser,
+        Scala3CompilerDiagnosticParser,
         AllCatchParser
     )
     private val IgnoredLines = listOf(

server/src/main/kotlin/org/jetbrains/bsp/bazel/server/diagnostics/Scala3CompilerDiagnosticParser.kt

@@ -0,0 +1,55 @@
+package org.jetbrains.bsp.bazel.server.diagnostics
+
+object Scala3CompilerDiagnosticParser : Parser {
+
+    override fun tryParse(output: Output): List<Diagnostic> =
+        listOfNotNull(tryParseOne(output))
+
+    private val DiagnosticHeader = """
+      ^--\       # "-- " diagnostic start 
+      \[E\d+\]   # "[E008]" code 
+      ([^:]+): # (1) type of diagnostic
+      ([^:]+):(\d+):(\d+) # (2) path, (3) line, (4) column
+      \ \-+$ # " -----------------" ending 
+      """.toRegex(RegexOption.COMMENTS)
+
+    // Scala 3 diagnostics have additional color printed, since Bazel uses renderedMessage field
+    private val colorRegex = "\u001b\\[1A\u001b\\[K|\u001B\\[[;\\d]*m".toRegex()
+
+    fun tryTake(output: Output, regex: Regex): MatchResult? =
+        output.peek()?.let { regex.matchEntire(it.replace(colorRegex, "")) }?.also { output.take() }
+
+    fun tryParseOne(output: Output): Diagnostic? {
+        return tryTake(output, DiagnosticHeader)
+            ?.let { match ->
+                val level = if (match.groupValues[1].contains("Error")) Level.Error else Level.Warning
+                val path = match.groupValues[2].trim()
+                val line = match.groupValues[3].toInt()
+                val messageLines = collectMessageLines(match.groupValues[1].trim(), output)
+                val column = match.groupValues[4].toIntOrNull() ?: tryFindColumnNumber(messageLines) ?: 1
+                val message = messageLines.joinToString("\n")
+                Diagnostic(Position(line, column), message, level, path, output.targetLabel)
+            }
+    }
+
+    private fun collectMessageLines(header: String, output: Output): List<String> {
+        val lines = mutableListOf<String>()
+        fun String.cleanLine(): String  =
+            this.replace(colorRegex, "").trim()
+
+        // skip lines with numbers which show the source and skip the next ^^^^ line
+        if (output.peek()?.cleanLine()?.startsWith('|') == false) output.take(2)
+        while (output.nonEmpty() && output.peek()?.cleanLine()?.startsWith('|') == true) {
+            lines.add(output.take().cleanLine().removePrefix("|").trim())
+        }
+        lines.add(0, header)
+        return lines
+    }
+
+    private val IssuePositionMarker = """^[\s\|]*\^\s*$""".toRegex() // ^ surrounded by whitespace only
+
+    private fun tryFindColumnNumber(messageLines: List<String>): Int? {
+        val line = messageLines.find { IssuePositionMarker.matches(it.replace(colorRegex, "")) }
+        return line?.indexOf("^")?.let { it + 1 }
+    }
+}

server/src/test/kotlin/org/jetbrains/bsp/bazel/server/diagnostics/DiagnosticsServiceTest.kt

@@ -358,6 +358,106 @@ class DiagnosticsServiceTest {
         )
         diagnostics shouldContainExactlyInAnyOrder expected
     }
+    @Test
+    fun `parse scala 3 error`() {
+        // given
+        val output = """
+            |-- [E007] Type Mismatch Error: Hello.scala:19:20 -------------------------------
+            |19 |  def hello4: Int = "Hello"
+            |   |                    ^^^^^^^
+            |   |                    Found:    ("Hello" : String)
+            |   |                    Required: Int
+            |   |
+            |   | longer explanation available when compiling with `-explain`
+            |2 errors found
+            |Build failed
+            |java.lang.RuntimeException: Build failed
+            |	at io.bazel.rulesscala.scalac.ScalacInvoker.invokeCompiler(ScalacInvoker3.java:43)
+            |	at io.bazel.rulesscala.scalac.ScalacWorker.compileScalaSources(ScalacWorker.java:253)
+            |	at io.bazel.rulesscala.scalac.ScalacWorker.work(ScalacWorker.java:69)
+            |	at io.bazel.rulesscala.worker.Worker.persistentWorkerMain(Worker.java:86)
+            |	at io.bazel.rulesscala.worker.Worker.workerMain(Worker.java:39)
+            |   at io.bazel.rulesscala.scalac.ScalacWorker.main(ScalacWorker.java:33)
+            """.trimMargin()
+
+        // when
+        val diagnostics = extractDiagnostics(output, "//project/src/main/scala/com/example/project:project")
+
+        // then
+        val expected = listOf(
+            PublishDiagnosticsParams(
+                TextDocumentIdentifier("file:///user/workspace/Hello.scala"),
+                BuildTargetIdentifier("//project/src/main/scala/com/example/project:project"),
+                ErrorDiagnostic(
+                    Position(19, 20),
+                    """|Type Mismatch Error
+                       |Found:    ("Hello" : String)
+                       |Required: Int
+                       |
+                       |longer explanation available when compiling with `-explain`""".trimMargin()
+                )
+            )
+        )
+        diagnostics shouldContainExactlyInAnyOrder expected
+    }
+
+    @Test
+    fun `parse scala 3 multiple errors`() {
+        // given
+        val output = """
+            |-- [E007] Type Mismatch Error: Hello.scala:18:20 -------------------------------
+            |18 |  def hello3: Int = "Hello"
+            |   |                    ^^^^^^^
+            |   |                    Found:    ("Hello" : String)
+            |   |                    Required: Int
+            |   |
+            |   | longer explanation available when compiling with `-explain`
+            |-- [E007] Type Mismatch Error: Hello.scala:19:20 -------------------------------
+            |19 |  def hello4: Int = "Hello"
+            |   |                    ^^^^^^^
+            |   |                    Found:    ("Hello" : String)
+            |   |                    Required: Int
+            |   |
+            |   | longer explanation available when compiling with `-explain`
+            |2 errors found
+            |Build failed
+            |java.lang.RuntimeException: Build failed
+            |	at io.bazel.rulesscala.scalac.ScalacInvoker.invokeCompiler(ScalacInvoker3.java:43)
+            |	at io.bazel.rulesscala.scalac.ScalacWorker.compileScalaSources(ScalacWorker.java:253)
+            |	at io.bazel.rulesscala.scalac.ScalacWorker.work(ScalacWorker.java:69)
+            |	at io.bazel.rulesscala.worker.Worker.persistentWorkerMain(Worker.java:86)
+            |	at io.bazel.rulesscala.worker.Worker.workerMain(Worker.java:39)
+            |at io.bazel.rulesscala.scalac.ScalacWorker.main(ScalacWorker.java:33)
+            """.trimMargin()
+
+        // when
+        val diagnostics = extractDiagnostics(output, "//project/src/main/scala/com/example/project:project")
+
+        // then
+        val expected = listOf(
+            PublishDiagnosticsParams(
+                TextDocumentIdentifier("file:///user/workspace/Hello.scala"),
+                BuildTargetIdentifier("//project/src/main/scala/com/example/project:project"),
+                ErrorDiagnostic(
+                    Position(18, 20),
+                    """|Type Mismatch Error
+                       |Found:    ("Hello" : String)
+                       |Required: Int
+                       |
+                       |longer explanation available when compiling with `-explain`""".trimMargin()
+                ),
+                ErrorDiagnostic(
+                    Position(19, 20),
+                    """|Type Mismatch Error
+                       |Found:    ("Hello" : String)
+                       |Required: Int
+                       |
+                       |longer explanation available when compiling with `-explain`""".trimMargin()
+                )
+            )
+        )
+        diagnostics shouldContainExactlyInAnyOrder expected
+    }
 
     @Test
     fun `parse scala warnings`() {