Support absolute path source locators (#5111)

The default behavior of Scala-cli is to use a Bloop server running in
the root directory for compilation. This results in absolute paths in
for source locators at compile time, but our logic had assumed we always
had relative paths and was manually stripping the leading forward slash
in source locator paths. Instead, we strip the leading forward slash for
relative paths by including it in the path prefix we remove, and then in
error reporting we add support for paths that are already absolute.

Author: jackkoenig

core/src/main/scala-2/chisel3/internal/SourceInfoFileResolver.scala

@@ -5,6 +5,8 @@ package chisel3.internal.sourceinfo
 import scala.language.experimental.macros
 import scala.reflect.macros.blackbox.Context
 
+import java.io.File.separatorChar
+
 ///////////////////////////////////////////////////////
 //                     WARNING!!                     //
 // This file is soft-linked into the compiler plugin //
@@ -13,13 +15,18 @@ import scala.reflect.macros.blackbox.Context
 
 /** Scala compile-time function for determine the String used to represent a source file path in SourceInfos */
 private[internal] object SourceInfoFileResolver {
+  // Ensure non-empty paths end in a slash
+  def sanitizePath(path: String): String = {
+    if (path.isEmpty) path
+    else if (path.last != separatorChar) path + separatorChar
+    else path
+  }
+
   def resolve(source: scala.reflect.internal.util.SourceFile): String = {
     val userDir = sys.props.get("user.dir") // Figure out what to do if not provided
     val projectRoot = sys.props.get("chisel.project.root")
-    val root = projectRoot.orElse(userDir)
+    val root = projectRoot.orElse(userDir).map(sanitizePath)
 
-    val path = root.map(r => source.file.canonicalPath.stripPrefix(r)).getOrElse(source.file.name)
-    val pathNoStartingSlash = if (path(0) == '/') path.tail else path
-    pathNoStartingSlash
+    root.map(r => source.file.canonicalPath.stripPrefix(r)).getOrElse(source.file.name)
   }
 }

core/src/main/scala/chisel3/internal/Error.scala

@@ -32,7 +32,12 @@ object ExceptionHelpers {
   private[chisel3] def getErrorLineInFile(sourceRoots: Seq[File], sl: SourceLine): List[String] = {
     def tryFileInSourceRoot(sourceRoot: File): Option[List[String]] = {
       try {
-        val file = new File(sourceRoot, sl.filename)
+        val file = {
+          val f = new File(sl.filename)
+          // Absolute paths are not relative to sourceRoot.
+          if (f.isAbsolute) f
+          else new File(sourceRoot, sl.filename)
+        }
         val lines = Source.fromFile(file).getLines()
         var i = 0
         while (i < (sl.line - 1) && lines.hasNext) {

lit/tests/ErrorCarat.sc

@@ -0,0 +1,17 @@
+// RUN: JDK_JAVA_OPTIONS='-Dchisel.project.root=' not scala-cli --server=false --java-home=%JAVAHOME --extra-jars=%RUNCLASSPATH --scala-version=%SCALAVERSION --scala-option="-Xplugin:%SCALAPLUGINJARS" %s | FileCheck %s
+// SPDX-License-Identifier: Apache-2.0
+
+import chisel3._
+
+class ModuleWithError extends Module {
+  val in = IO(Input(UInt(8.W)))
+  val out = IO(Output(UInt(16.W)))
+
+  // Check behavior of absolute path source locators due to chisel.project.root set to empty above.
+  // CHECK:      High index 15 is out of range [0, 7]
+  // CHECK-NEXT: out := in(15, 0)
+  // CHECK-NEXT:          ^
+  out := in(15, 0)
+}
+
+circt.stage.ChiselStage.emitCHIRRTL(new ModuleWithError)