Better error message on missing BlackBox resource

This wraps interactions with a BlackBox resource file such that a
FileNotFoundException are wrapped in a BlackBoxNotFoundException and
rethrown. This provides a better, verbose error message to the user and avoids a
FileNotFoundException showing up as an internal FIRRTL error.

This adds tests that the expected exception is thrown for both
BlackBoxResourceAnno and BlackBoxResourceAnno.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

2 files changed, 41 insertions, 6 deletions

diff --git a/src/main/scala/firrtl/transforms/BlackBoxSourceHelper.scala b/src/main/scala/firrtl/transforms/BlackBoxSourceHelper.scala
index bf419840..31c2a04b 100644
--- a/src/main/scala/firrtl/transforms/BlackBoxSourceHelper.scala
+++ b/src/main/scala/firrtl/transforms/BlackBoxSourceHelper.scala
@@ -35,6 +35,13 @@ case class BlackBoxPathAnno(target: ModuleName, path: String) extends BlackBoxHe
   override def serialize: String = s"path\n$path"
 }
 
+/** Exception indicating that a blackbox wasn't found
+  * @param fileName the name of the BlackBox file (only used for error message generation)
+  * @param e an underlying exception that generated this
+  */
+class BlackBoxNotFoundException(fileName: String, e: Throwable = null) extends FIRRTLException(
+  s"BlackBox '$fileName' not found. Did you misspell it? Is it in src/{main,test}/resources?", e)
+
 /** Handle source for Verilog ExtModules (BlackBoxes)
   *
   * This transform handles the moving of Verilog source for black boxes into the
@@ -70,6 +77,7 @@ class BlackBoxSourceHelper extends firrtl.Transform {
     * @note the state is not changed by this transform
     * @param state Input Firrtl AST
     * @return A transformed Firrtl AST
+    * @throws BlackBoxNotFoundException if a Verilog source cannot be found
     */
   override def execute(state: CircuitState): CircuitState = {
     val (annos, targetDir) = collectAnnos(state.annotations)
@@ -82,7 +90,7 @@ class BlackBoxSourceHelper extends firrtl.Transform {
         val fromFile = new File(path)
         val toFile = new File(targetDir, fileName)
 
-        val inputStream = new FileInputStream(fromFile).getChannel
+        val inputStream = BlackBoxSourceHelper.safeFile(fromFile.toString)(new FileInputStream(fromFile).getChannel)
         val outputStream = new FileOutputStream(toFile).getChannel
         outputStream.transferFrom(inputStream, 0, Long.MaxValue)
 
@@ -105,6 +113,16 @@ class BlackBoxSourceHelper extends firrtl.Transform {
 }
 
 object BlackBoxSourceHelper {
+  /** Safely access a file converting [[FileNotFoundException]]s and [[NullPointerException]]s into
+    * [[BlackBoxNotFoundException]]s
+    * @param fileName the name of the file to be accessed (only used for error message generation)
+    * @param code some code to run
+    */
+  private def safeFile[A](fileName: String)(code: => A) = try { code } catch {
+    case e@ (_: FileNotFoundException | _: NullPointerException) => throw new BlackBoxNotFoundException(fileName, e)
+    case t: Throwable                                            => throw t
+  }
+
   /**
     * finds the named resource and writes into the directory
     * @param name the name of the resource
@@ -122,14 +140,12 @@ object BlackBoxSourceHelper {
     * finds the named resource and writes into the directory
     * @param name the name of the resource
     * @param file the file to write it into
+    * @throws BlackBoxNotFoundException if the requested resource does not exist
     */
   def copyResourceToFile(name: String, file: File) {
     val in = getClass.getResourceAsStream(name)
-    if (in == null) {
-      throw new FileNotFoundException(s"Resource '$name'")
-    }
     val out = new FileOutputStream(file)
-    Iterator.continually(in.read).takeWhile(-1 != _).foreach(out.write)
+    safeFile(name)(Iterator.continually(in.read).takeWhile(-1 != _).foreach(out.write))
     out.close()
   }
 
diff --git a/src/test/scala/firrtlTests/transforms/BlacklBoxSourceHelperSpec.scala b/src/test/scala/firrtlTests/transforms/BlacklBoxSourceHelperSpec.scala
index 7daebf21..c6918624 100644
--- a/src/test/scala/firrtlTests/transforms/BlacklBoxSourceHelperSpec.scala
+++ b/src/test/scala/firrtlTests/transforms/BlacklBoxSourceHelperSpec.scala
@@ -105,5 +105,24 @@ class BlacklBoxSourceHelperTransformSpec extends LowTransformSpec {
     val verilogCompiler = new VerilogEmitter
     verilogCompiler.transforms.map { x => x.getClass } should contain (classOf[BlackBoxSourceHelper])
   }
-}
 
+  behavior of "BlackBox resources that do not exist"
+
+  it should "provide a useful error message for BlackBoxResourceAnno" in {
+    val annos = Seq( BlackBoxTargetDirAnno("test_run_dir"),
+                     BlackBoxResourceAnno(moduleName, "/blackboxes/IDontExist.v") )
+
+    (the [BlackBoxNotFoundException] thrownBy { execute(input, "", annos) })
+      .getMessage should include ("Did you misspell it?")
+  }
+
+  it should "provide a useful error message for BlackBoxPathAnno" in {
+    val absPath = new java.io.File("src/test/resources/blackboxes/IDontExist.v").getCanonicalPath
+    val annos = Seq( BlackBoxTargetDirAnno("test_run_dir"),
+                     BlackBoxPathAnno(moduleName, absPath) )
+
+    (the [BlackBoxNotFoundException] thrownBy { execute(input, "", annos) })
+      .getMessage should include ("Did you misspell it?")
+  }
+
+}