Improve compiler's diagnostic messages

engine/runtime/src/main/scala/org/enso/compiler/Compiler.scala

@@ -1,7 +1,7 @@
 package org.enso.compiler
 
 import com.oracle.truffle.api.TruffleLogger
-import com.oracle.truffle.api.source.Source
+import com.oracle.truffle.api.source.{Source}
 import org.enso.compiler.codegen.{IrToTruffle, RuntimeStubsGenerator}
 import org.enso.compiler.context.{FreshNameSupply, InlineContext, ModuleContext}
 import org.enso.compiler.core.IR
@@ -34,7 +34,6 @@ import java.util.concurrent.{
   TimeUnit
 }
 import java.util.logging.Level
-
 import scala.jdk.OptionConverters._
 import java.util.concurrent.Future
 
@@ -985,25 +984,8 @@ class Compiler(
     diagnostics: List[IR.Diagnostic],
     source: Source
   ): Boolean = {
-    val errors   = diagnostics.collect { case e: IR.Error => e }
-    val warnings = diagnostics.collect { case w: IR.Warning => w }
-
-    if (warnings.nonEmpty) {
-      output.println("Compiler encountered warnings:")
-      warnings.foreach { warning =>
-        output.println(formatDiagnostic(warning, source))
-      }
-    }
-
-    if (errors.nonEmpty) {
-      output.println("Compiler encountered errors:")
-      errors.foreach { error =>
-        output.println(formatDiagnostic(error, source))
-      }
-      true
-    } else {
-      false
-    }
+    diagnostics.foreach(diag => output.println(formatDiagnostic(diag, source)))
+    diagnostics.exists(_.isInstanceOf[IR.Error])
   }
 
   /** Pretty prints compiler diagnostics.
@@ -1016,10 +998,68 @@ class Compiler(
     diagnostic: IR.Diagnostic,
     source: Source
   ): String = {
-    fileLocationFromSection(
-      diagnostic.location,
-      source
-    ) + ": " + diagnostic.formattedMessage
+    val outSupportsAnsiColors = System.console() != null
+    val ansiReset             = "\u001B[0m"
+    val ansiRed               = "\u001B[31m"
+    val ansiYellow            = "\u001B[33m"
+    val ansiBold              = "\u001B[1m"
+
+    def yellowBold(text: String) =
+      if (outSupportsAnsiColors) ansiYellow + ansiBold + text + ansiReset
+      else text
+    def redBold(text: String) =
+      if (outSupportsAnsiColors) ansiRed + ansiBold + text + ansiReset else text
+    def bold(text: String) =
+      if (outSupportsAnsiColors) ansiBold + text + ansiReset else text
+
+    val (coloredFunc, subject) = diagnostic match {
+      case _: IR.Error   => (redBold _, "error: ")
+      case _: IR.Warning => (yellowBold _, "warning: ")
+      case _             => throw new IllegalStateException("Unexpected diagnostic type")
+    }
+
+    diagnostic.location match {
+      case Some(location) =>
+        val section   = source.createSection(location.start, location.length)
+        val isOneLine = section.getStartLine == section.getEndLine
+        if (isOneLine) {
+          val lineNumber  = section.getStartLine
+          val startColumn = section.getStartColumn
+          val endColumn   = section.getEndColumn
+          val sectionLen  = endColumn - startColumn
+          val line        = source.createSection(lineNumber).getCharacters.toString
+          val sb          = new StringBuilder()
+          sb
+            .append(
+              bold(
+                source.getName + ":" + lineNumber + ":" + startColumn + "-" + endColumn + ": "
+              )
+            )
+            .append(coloredFunc(subject))
+            .append(diagnostic.formattedMessage)
+            .append("\n")
+          sb
+            .append(line.substring(0, startColumn - 1))
+            .append(coloredFunc(line.substring(startColumn - 1, endColumn)))
+            .append(line.substring(endColumn))
+            .append("\n")
+          sb
+            .append(" " * (startColumn - 1))
+            .append(coloredFunc("^" + "~" * sectionLen))
+          sb.toString
+        } else {
+          bold(fileLocationFromSection(diagnostic.location, source)) +
+          ": " +
+          coloredFunc(subject) +
+          diagnostic.formattedMessage
+        }
+      case None =>
+        // We dont have location information, so we just print the message
+        bold(fileLocationFromSection(diagnostic.location, source)) +
+        ": " +
+        coloredFunc(subject)
+        diagnostic.formattedMessage
+    }
   }
 
   private def fileLocationFromSection(

engine/runtime/src/test/scala/org/enso/interpreter/test/semantic/ImportsTest.scala

@@ -27,7 +27,7 @@ class ImportsTest extends PackageTest {
   "Import statements" should "report errors when they cannot be resolved" in {
     the[InterpreterException] thrownBy evalTestProject(
       "Test_Bad_Imports"
-    ) should have message "Compilation aborted due to errors."
+    ) should have message "Aborting due to"
     val outLines = consumeOut
     outLines(2) should include(
       "Package containing the module Surely_This.Does_Not_Exist.My_Module " +
@@ -124,7 +124,7 @@ class ImportsTest extends PackageTest {
       "TestSubmodulesNameConflict"
     ) should have message "Method `c_mod_method` of type C.type could not be found."
     val outLines = consumeOut
-    outLines(2) should include
+    outLines(1) should include
     "Declaration of type C shadows module local.TestSubmodulesNameConflict.A.B.C making it inaccessible via a qualified name."
   }
 
@@ -160,10 +160,10 @@ class ImportsTest extends PackageTest {
       "Test_Polyglot_Exports"
     ) should have message "Compilation aborted due to errors."
     val outLines = consumeOut
-    outLines should have length 3
+    outLines should have length 4
     outLines(
-      2
-    ) shouldEqual "Main.enso[5:16-5:19]: The name `Long` could not be found."
+      1
+    ) shouldEqual "Main.enso:5:16-19: error: The name `Long` could not be found."
   }
 
   "Constructors" should "be importable" in {
@@ -180,10 +180,10 @@ class ImportsTest extends PackageTest {
     ) should have message "Compilation aborted due to errors."
 
     val outLines = consumeOut
-    outLines should have length 3
+    outLines should have length 4
     outLines(
       2
-    ) shouldEqual "Main.enso[2:14-2:17]: Fully qualified name references a library Standard.Base but an import statement for it is missing."
+    ) shouldEqual "Main.enso:2:14-17: error: Fully qualified name references a library Standard.Base but an import statement for it is missing."
   }
 
   "Fully qualified names" should "be resolved when library has already been loaded" in {
@@ -200,10 +200,10 @@ class ImportsTest extends PackageTest {
       "Test_Fully_Qualified_Name_Conflict"
     ) should have message "Method `Foo` of type Atom.type could not be found."
     val outLines = consumeOut
-    outLines should have length 3
+    outLines should have length 4
     outLines(
-      2
-    ) shouldEqual "Main.enso[2:1-2:57]: The exported type `Atom` in `local.Test_Fully_Qualified_Name_Conflict.Atom` module will cause name conflict when attempting to use a fully qualified name of the `local.Test_Fully_Qualified_Name_Conflict.Atom.Foo` module."
+      1
+    ) shouldEqual "Main.enso:2:1-57: error: The exported type `Atom` in `local.Test_Fully_Qualified_Name_Conflict.Atom` module will cause name conflict when attempting to use a fully qualified name of the `local.Test_Fully_Qualified_Name_Conflict.Atom.Foo` module."
   }
 
   "Deeply nested modules" should "infer correct synthetic modules" in {