Improve error reporting

[lukexi]

As seen in #31, stack-ide fails to report configuration errors at startup, and instead responds with

{"tag":"ResponseWelcome","contents":[0,1,0]}
{"tag":"ResponseUpdateSession","contents":null}

(without compiling anything)

A call to "RequestGetSourceErrors" works to trigger an actual helpful error, e.g.:
{"tag":"RequestGetSourceErrors","contents":[]} {"tag":"ResponseGetSourceErrors","contents":[{"errorSpan":{"tag":"TextSpan","contents":"<<server died>>"},"errorKind":"KindServerDied","errorMsg":"/Users/lukexi/.stack/snapshots/x86_64-osx/lts-2.17/7.8.4/pkgdb/package.cache: GHC.PackageDb.readPackageDb: inappropriate type (not a ghc-pkg db file, wrong file magic number)"}]}

It would be great to find a way to trigger the error immediately on startup.

(I'll create a separate issue on ide-backend for the particular error in the example, which can be solved by making sure the project is using the same snapshot that ide-backend was built against — do we need a separate version of ide-backend-server for each package db?)

[mgsloan]

I recently created an ide-backend issue that ought to cover this - does it? fpco/ide-backend#292

do we need a separate version of ide-backend-server for each package db?

I think we'd just need a separate version of ide-backend-server for each ghc version

[mgsloan]

I've added more detailed progress reporting for recompilation, including better reporting of failure cases and server restarts: fpco/ide-backend@702082d

I've also added logging, and plumbed it through stack-ide as ResponseLog messages: fpco/ide-backend@0c61a1f 7c81675

Finally, I removed KindServerDied, which doesn't seem like the right way to solve this: fpco/ide-backend@b7e5460

Do these changes address the problem adequately?

[lukexi]

Hi Michael,
Yep, that's looking awesome. I can send the logs to the Sublime console and that'll be super helpful for debugging failures. It also reports startup failure right away as I hoped : ). Thanks a bunch!