There are a few different times when we detect duplicate compiler
extensions.
(a) We detect them in Plugin.registerCompiler if a single
isopack itself registers duplicate extensions.
(b) When compiling a unibuild in compiler.compile, we check to see if a unibuild's
plugin-providing dependencies overlap.
(c) When preparing a unibuild for bundle-time source processing, we
check the same condition.
(Why do we need to re-check in (c)? If a unibuild was published and
passed (b) at publish time but is being bundled with different versions
of dependencies, it might fail (c).)
There were a few fixes here:
- In compiler.js (b), if we detected a duplicate extension, the code to get
the name of the conflict package was wrong and could throw.
- In compiler-plugin (c), we just weren't using buildmessage.
With just those fixes, we would actually see *both* kind of errors show
up if the error was in the app rather than a package, because
bundler.bundle didn't actually bail out on error after compiler.compile!
So we added that fix too, with a relatively conservative WatchSet.
05366ab5c2