Support command:pickRemoteProcess

[zed0]

Functionality

The little documented pickRemoteProcess command can be used with the pipeTransport option to query processes running on a potentially remote host rather than the local machine.

This effectively works by running the command to list processes in the same environment that the debugger will be run in.

See https://code.visualstudio.com/docs/cpp/pipe-transport for details.

Implementation

In order to pick a remote process it's necessary to know the rest of the pipeTransport configuration. This is currently achieved by passing the un-expanded configuration to the expand_config_variables function and each of the functions in var_placeholders_once. I'm not sure if there's a better way of doing this that would allow placeholders within the pipeTransport configuration to be used.

Reproduction

An example config might look like:

    {
      "name": "C++ Attach in hello_gdb container",
      "type": "cppdbg",
      "request": "attach",
      "program": "/hello.out",
      "processId": "${command:pickRemoteProcess}",
      "pipeTransport": {
          "pipeCwd": "${workspaceRoot}",
          "pipeProgram": "docker",
          "pipeArgs": [
              "exec", 
              "-i", 
              "hello_gdb", 
              "sh",
              "-c"
          ],
          "debuggerPath": "/usr/bin/gdb"
      },
      "sourceFileMap": {
              "/src":"${workspaceRoot}"
      },
      "linux": {
        "MIMode": "gdb"
      },
      "setupCommands": [
        {
          "description": "Enable pretty-printing for gdb",
          "text": "-enable-pretty-printing",
          "ignoreFailures": true
        }
      ]
    }

This is adapted from launch.json in https://github.com/andyneff/hello-world-gdb which also has a docker container that can be used to test the functionality.

[mfussenegger]

Thanks for the PR but I'm afraid I can't merge this. debug adapter specific functionality is out of scope for nvim-dap and the pipeTransport property is adapter specific.

You'll instead have to use a function value as property and do this in your configuration or plugin

See also:

• When is configuration evaluated? #597 (comment)
• Support __call metatable on configuration #768
• Add hooks for preLaunchTask and postDebugTask #720

[zed0]

I had assumed that pickRemoteProcess fell into the same category as pickProcess which is already implemented.
Thanks for taking a look anyway, I'll have a look at the comments you've provided and update https://github.com/mfussenegger/nvim-dap/wiki/C-C---Rust-(gdb-via--vscode-cpptools) with the results.

[mfussenegger]

I had assumed that pickRemoteProcess fell into the same category as pickProcess which is already implemented.

It's indeed similar but for me the key difference is that pickProcess has no dependency on concrete configuration properties
In vscode it's also part of the cpptools extension: https://github.com/microsoft/vscode-cpptools/blob/20e220354d3e3a918fef25137c1b4f0e4545c45b/Extension/package.json#L3152 & https://github.com/microsoft/vscode-cpptools/blob/48653c0854c2b923da7d149505f62a0f1967c2b3/Extension/src/Debugger/extension.ts#L39

I guess nvim-dap could provide a hook to register variable handlers too.
I'll consider that for #720

[zed0]

I guess nvim-dap could provide a hook to register variable handlers too.
I'll consider that for #720

That does sound pretty useful, for all sorts of adapters.