Naming Prefix Preserved Across Failing Tests

[seldridge]

If an exception occurs during the elaboration of a Chisel module, the naming prefix is not cleared. This can then leak the prefix to later invocations of the same builder.

I noticed this when dealing with a long string of failing Scalatest tests within the same test suite. As this is kind of weird, I put this on a branch here: https://github.com/chipsalliance/chisel/pull/new/dev/chisel-naming-prefix-bug

Snippet from that branch below:

  behavior.of("Failed earlier tests")

  it should "A" in {
    class Foo extends RawModule {
      override def localModulePrefix = Some("A")
      throw new Exception("A")
    }
    intercept[Exception] {
      ChiselStage.elaborate(new Foo)
    }
  }

  it should "B" in {
    class Foo extends RawModule {
      override def localModulePrefix = Some("B")
    }

    ChiselStage
      .emitCHIRRTL(new Foo)
      .fileCheck()("CHECK: module B_Foo")
  }

This will generate a module A_B_Foo when it should be a module B_Foo.

To run the example on the branch:

./mill 'chisel[2.13.16].test.testOnly' chiselTests.ModulePrefixSpec -- -z "Failed earlier tests"