Issues with BSP `workspace/reload`

[ckipp01]

So after playing around a fair bit with mill-bsp it seems that the reload functionality isn't quite working as I originally thought it does. It's a bit decieving since according to here:

https://github.com/com-lihaoyi/mill/blob/c3b64a54be184d9d41b219d84761479dd61f10af/bsp/src/mill/bsp/MillBuildServer.scala#L303-L313

It doesn't do anything but send back an {}. Metals then interprets this as a successful reload and moves on, when really this may not be a successful reload. You can can see this for example if you misspell something like tesFrameworks and hit save. Metals will prompt you to re-import with under the hood triggers a workspace/reload to which Mill immediately returns {} making metals think everything is ok. If I remember the conversation correctly the idea was the shut down and restart, but that also doesn't fully seem to be happening when looking at the bsp logs after a reload.

For example if I edit the build.sc with something invalid and trigger a reload I'll see this:

[Trace - 11:02:13 PM] Sending request 'workspace/reload - (14)'
Params: null


[Trace - 11:02:13 PM] Received response 'workspace/reload - (14)' in 2ms
Result: {}
Error: null


[Trace - 11:02:14 PM] Sending request 'buildTarget/scalaMainClasses - (15)'

Reload happens, Metals is happy and then Mill starts answers the requests for the main classes and tests classes. It doesn't seem to shut down and it's actually in a somewhat invalid state where the build is invalid, but Metals is still working off the last working state. I've also seen this cause you to get into a loop where you close the project, and then the next time you attempt to re-open it fails to get any build targets, and then re-initializes over and over.

2021.11.29 23:06:41 INFO  Attempting to connect to the build server...
2021.11.29 23:06:41 INFO  tracing is enabled: /Users/ckipp/Documents/scala-workspace/mill-minimal/.metals/bsp.trace.json
2021.11.29 23:06:40 WARN  No build session currently active to reload.
2021.11.29 23:06:41 INFO  time: Connected to build server in 0.91s
2021.11.29 23:06:41 INFO  Connected to Build server: mill-bsp v0.10.0-M4
2021.11.29 23:06:47 INFO  tracing is enabled: /Users/ckipp/Documents/scala-workspace/mill-minimal/.metals/bsp.trace.json
2021.11.29 23:06:47 INFO  Connected to Build server: mill-bsp v0.10.0-M4
2021.11.29 23:06:49 INFO  no build target: using presentation compiler with only scala-library: 2.13.7
2021.11.29 23:06:49 INFO  time: code lens generation in 3.77s
2021.11.29 23:06:51 INFO  no build target: using presentation compiler with only scala-library: 2.13.7
2021.11.29 23:06:52 INFO  tracing is enabled: /Users/ckipp/Documents/scala-workspace/mill-minimal/.metals/bsp.trace.json
2021.11.29 23:06:52 INFO  Connected to Build server: mill-bsp v0.10.0-M4
2021.11.29 23:06:56 INFO  shutting down Metals
2021.11.29 23:06:56 INFO  Shut down connection with build server.
2021.11.29 23:06:56 INFO  Disconnecting from mill-bsp session...

Here are some more bsp trace files showing this:

BSP TRACE

[Trace - 11:06:41 PM] Sending request 'build/initialize - (1)'
Params: {
  "rootUri": "file:///Users/ckipp/Documents/scala-workspace/mill-minimal/",
  "displayName": "Metals",
  "version": "0.10.9+80-6ff28e97-SNAPSHOT",
  "bspVersion": "2.0.0-M15",
  "capabilities": {
    "languageIds": [
      "scala"
    ]
  },
  "data": {
    "semanticdbVersion": "4.4.30",
    "supportedScalaVersions": [
      "2.13.7",
      "2.12.15",
      "2.12.14",
      "2.12.13",
      "2.12.12",
      "2.12.11",
      "2.13.4",
      "2.13.5",
      "2.13.6",
      "2.11.12",
      "2.12.8",
      "2.12.9",
      "2.12.10",
      "2.13.0",
      "2.13.1",
      "2.13.2",
      "2.13.3"
    ]
  }
}


[Trace - 11:06:42 PM] Received response 'build/initialize - (1)' in 836ms
Result: {
  "displayName": "mill-bsp",
  "version": "0.10.0-M4",
  "bspVersion": "2.0.0",
  "capabilities": {
    "compileProvider": {
      "languageIds": [
        "java",
        "scala"
      ]
    },
    "testProvider": {
      "languageIds": [
        "java",
        "scala"
      ]
    },
    "runProvider": {
      "languageIds": [
        "java",
        "scala"
      ]
    },
    "debugProvider": {
      "languageIds": []
    },
    "inverseSourcesProvider": true,
    "dependencySourcesProvider": true,
    "dependencyModulesProvider": true,
    "resourcesProvider": true,
    "buildTargetChangedProvider": false,
    "canReload": true
  }
}
Error: null


[Trace - 11:06:42 PM] Sending notification 'build/initialized'
Params: null


[Trace - 11:06:42 PM] Sending request 'workspace/buildTargets - (2)'
Params: null


[Trace - 11:06:47 PM] Sending request 'build/initialize - (1)'
Params: {
  "rootUri": "file:///Users/ckipp/Documents/scala-workspace/mill-minimal/",
  "displayName": "Metals",
  "version": "0.10.9+80-6ff28e97-SNAPSHOT",
  "bspVersion": "2.0.0-M15",
  "capabilities": {
    "languageIds": [
      "scala"
    ]
  },
  "data": {
    "semanticdbVersion": "4.4.30",
    "supportedScalaVersions": [
      "2.13.7",
      "2.12.15",
      "2.12.14",
      "2.12.13",
      "2.12.12",
      "2.12.11",
      "2.13.4",
      "2.13.5",
      "2.13.6",
      "2.11.12",
      "2.12.8",
      "2.12.9",
      "2.12.10",
      "2.13.0",
      "2.13.1",
      "2.13.2",
      "2.13.3"
    ]
  }
}


[Trace - 11:06:47 PM] Received response 'build/initialize - (1)' in 697ms
Result: {
  "displayName": "mill-bsp",
  "version": "0.10.0-M4",
  "bspVersion": "2.0.0",
  "capabilities": {
    "compileProvider": {
      "languageIds": [
        "java",
        "scala"
      ]
    },
    "testProvider": {
      "languageIds": [
        "java",
        "scala"
      ]
    },
    "runProvider": {
      "languageIds": [
        "java",
        "scala"
      ]
    },
    "debugProvider": {
      "languageIds": []
    },
    "inverseSourcesProvider": true,
    "dependencySourcesProvider": true,
    "dependencyModulesProvider": true,
    "resourcesProvider": true,
    "buildTargetChangedProvider": false,
    "canReload": true
  }
}
Error: null


[Trace - 11:06:47 PM] Sending notification 'build/initialized'
Params: null


[Trace - 11:06:50 PM] Sending request 'workspace/buildTargets - (2)'
Params: null


[Trace - 11:06:52 PM] Sending request 'build/initialize - (1)'
Params: {
  "rootUri": "file:///Users/ckipp/Documents/scala-workspace/mill-minimal/",
  "displayName": "Metals",
  "version": "0.10.9+80-6ff28e97-SNAPSHOT",
  "bspVersion": "2.0.0-M15",
  "capabilities": {
    "languageIds": [
      "scala"
    ]
  },
  "data": {
    "semanticdbVersion": "4.4.30",
    "supportedScalaVersions": [
      "2.13.7",
      "2.12.15",
      "2.12.14",
      "2.12.13",
      "2.12.12",
      "2.12.11",
      "2.13.4",
      "2.13.5",
      "2.13.6",
      "2.11.12",
      "2.12.8",
      "2.12.9",
      "2.12.10",
      "2.13.0",
      "2.13.1",
      "2.13.2",
      "2.13.3"
    ]
  }
}


[Trace - 11:06:53 PM] Received response 'build/initialize - (1)' in 753ms
Result: {
  "displayName": "mill-bsp",
  "version": "0.10.0-M4",
  "bspVersion": "2.0.0",
  "capabilities": {
    "compileProvider": {
      "languageIds": [
        "java",
        "scala"
      ]
    },
    "testProvider": {
      "languageIds": [
        "java",
        "scala"
      ]
    },
    "runProvider": {
      "languageIds": [
        "java",
        "scala"
      ]
    },
    "debugProvider": {
      "languageIds": []
    },
    "inverseSourcesProvider": true,
    "dependencySourcesProvider": true,
    "dependencyModulesProvider": true,
    "resourcesProvider": true,
    "buildTargetChangedProvider": false,
    "canReload": true
  }
}
Error: null


[Trace - 11:06:53 PM] Sending notification 'build/initialized'
Params: null

[lefou]

Thanks for the nice report. This looks like a duplicate of #1560.

[ckipp01]

Thanks for the nice report. This looks like a duplicate of #1560.

Ahh sorry, I totally missed that one. Since there is quite a bit of info in here I'll leave it up, but if you prefer I an also just port this all over there.