Better debugging output

[lionel-rowe]

Currently, thrown errors usually give very little information about what's gone wrong. Most errors look like this:

error: Uncaught (in promise) Error: Unable to output during bundling.
      const ret = new Error(getStringFromWasm0(arg0, arg1));
      # ...stack trace of WASM output/JS glue code

That could be any of the following situations:

• Entry point doesn't exist
• An imported module doesn't exist
• Syntax error in any imported file
• An imported module relies on an import map that hasn't been passed to bundle
• Probably any number of other situations

Is there any way this debugging info could be provided? Or at least a stack trace that gives the file name/line number where the problem occurs within the bundled modules, rather than in the WASM output/JS glue code.

[yacinehmito]

I agree, this is a real problem. I am currently stuck on a dependency that deno_emit doesn't want to bundle and I have no idea where to start. 😞

Unfortunately my knowledge of Wasm and Rust is too limited to be helpful. @dsherret Would you be able to provide some pointers on how to make this better?