vimspector/docs/configuration.md

title
Configuration

This document defines the supported format for project and adapter configuration for Vimspector.

Concepts

As Vimspector supports debugging arbitrary projects, you need to tell it a few deatils about what you want to debug, and how to go about doing that.

In order to debug things, Vimspector requires a Debug Adapter which bridges between Vimspector and the actual debugger tool. Vimspector can be used with any debug adapter that implements the Debug Adapter Protocol.

For each debugging session, you provide a debug configuration which includes things like:

• The debug adapter to use (and possibly how to launch and configure it).
• How to connect to the remote host, if remote debugging.
• How to launch or attach to your process.

Along with optional additional configuration for things like:

• Exception breakpoints

Debug adapter configuration

The adapter to use for a particular debug session can be specified inline within the debug configuration, but more usually the debug adapter is defined separately and just referenced from the debug configuration.

The adapter configuration includes things like:

• How to launch or connect to the debug adapter
• How to configure it for PID attachment
• How to set up remote debugging, such as how to launch the process remotely (for example, under gdbserver, ptvsd, etc.)

Debug profile configuration

Projects can have many different debug profiles. For example you might have all of the following, for a given source tree:

• Remotely launch c++ the process, and break on main
• Locally Python test and break exception
• Remotely attach to a c++ process
• Locally launch a bash script
• Attach to a JVM listening on a port

Each of these represents a different use case and a different debug configuration. As mentioned above, a debug configuration is essentially:

• The adapter to use
• The type of session (launch or attach), and whether or not to do it remotely
• The configuration to pass to the adapter in order to launch or attach to the process.

The bulk of the configuration is the last of these, which comprises adapter-specific options, as the Debug Adapter Protocol does not specify any standard for launch or attach configuration.

Replacements and variables

Vimspector debug configuration is intended to be as general as possible, and to be committed to source control so that debugging your applications becomes a simple, quick and pain-free habit (e.g. answering questions like "what happens if..." with "just hit F5 and step through!").

Therefore it's important to abstract certain details, like runtime and build-time paths, and to parameterise the debug configuration. Vimspector provides a simple mechanism to do this with ${replacement} style replacements.

The values available within the ${...} are defined below, but in summary the following are supported:

• Environment variables, such as ${PATH}
• Predefined variables, such as ${workspaceRoot}, ${file} etc.
• Configuration-defined variables, either provided by the adapter configuration or debug configuration, or from running a simple shell command.
• Anything else you like - the user will be asked to provide a value.

If the latter 2 are confusing, for now, suffice to say that they are how Vimspector allows parameterisation of debug sessions. The [Vimspector website][website-getting-started] has a good example of where this sort of thing is useful: accepting the name of a test to run.

But for now, consider the following example snippet:

{
  "configurations": {
    "example-debug-configuration": {
      "adapter": "example-adapter-name",
      "variables": {
        "SecretToken": {
          "shell" : [ "cat", "${HOME}/.secret_token" ]
        }
      },
      "configuration": {
        "request": "launch",
        "program": [
          "${fileBasenameNoExtension}",
          "-c", "configuration_file.cfg",
          "-u", "${USER}",
          "--test-identifier", "${TestIdentifier}",
          "--secret-token", "${SecretToken}"
        ]
      },
      "breakpoints": {
        "exception": {
          "caught": "",
          "uncaught": "Y"
        }
      }
    }
  }
}

In this (fictitious) example the program launch configuration item contains the following variable substitutions:

• ${fileBasenameNoExtension} - this is a Predefined Variable, set by Vimspector to the base name of the file that's opened in Vim, with its extension removed (/path/to/xyz.cc -> xyz).
• ${USER} - this refers to the Environment Variable USER.
• ${TestIdentifier} - this variable is not defined, so the user is asked to provide a value interactively when starting debugging. Vimspector remembers what they said and provides it as the default should they debug again.
• ${SecretToken} - this variable is provided by the configuration's variables block. Its value is taken from the stripped result of running the shell command. Note these variables can be supplied by both the debug and adapter configurations and can be either static strings or shell commands.

Configuration Format

All Vimspector configuration is defined in a JSON object. The complete specification of this object is available in the JSON Schema, but the basic format for the configuration object is:

{
  "adapters": { <object mapping name to <adapter configuration> },
  "configurations": { <object mapping name to <debug configuration> }
}

The adapters key is actually optional, as <adapter configuration> can be embedded within <debug configuration>, though this is not recommended usage.

Files and locations

The above configuration object is constructed from a number of configuration files, by merging objects i specified order.

In a minimal sense, the only file required is a .vimspector.json file in the root of your project which defines the full configuration object, but it is usually useful to split the adapters configuration into a separate file (or indeed one file per debug adapter).

The following sections describe the files that are read and use the following abbreviations:

• <vimspector home> means the path to the Vimspector installation (such as $HOME/.vim/pack/vimspector/start/vimspector)
• <OS> is either macos or linux depending on the host operating system.

Adapter configurations

Vimspector reads a series of files to build the adapters object. The adapters objects are merged in such a way that a definition for an adapter named example-adapter in a later file completely replaces a previous definition.

• <vimspector home>/gadgets/<OS>/.gadgets.json - the file written by install_gadget.py and not usually edited by users.
• <vimspector home>/gadgets/<OS>/.gadgets.d/*.json (sorted alphabetically). These files are user-supplied and override the above.
• The first such .gadgets.json file found in all parent directories of the file open in Vim.
• The .vimspector.json (see below)

In all cases, the required format is:

{
  "$schema": "https://puremourning.github.io/vimspector/schema/gadgets.schema.json#",
  "adapters": {
    "<adapter name>": {
      <adapter configuration>
    }
  }
}

Each adapters block can define any number of adapters. As mentioned, if the same adapter name exists in multiple files, the last one read takes precedence and completely replaces the previous configuration. In particular that means you can't just override one option, you have to override the whole block.

Adapter configurations are re-read at the start of each debug session.

The specification for the gadget object is defined in the [gadget schema][].

Debug configurations

The debug configurations are read from .vimspector.json. The file is found (like .gadgets.json above) by recursively searching up the directory hierarchy from the directory of the file open in Vim. The first file found is read and no further searching is done.

Only a single .vimspector.json is read.

Debug configurations are re-read at the start of each debug session.

The specification for the gadget object is defined in the schema, but a typical example looks like this:

{
  "$schema": "https://puremourning.github.io/vimspector/schema/vimspector.schema.json#",
  "configurations": {
    "<configuation name>": {
      "adapter": "<adapter name>",
      "configuration": {
        "request": "<launch or attach>",
        <debug configutation>
      }
    }
  }
}

Predefined Variables

The following variables are provided:

• ${dollar} - has the value $, can be used to enter a literal dollar
• $$ - a literal dollar
• ${workspaceRoot} - the path of the folder where .vimspector.json was found
• ${workspaceFolder} - the path of the folder where .vimspector.json was found
• ${gadgetDir} - path to the OS-specifc gadget dir (<vimspector home>/gadgets/<OS>)
• ${file} - the current opened file
• ${relativeFile} - the current opened file relative to workspaceRoot
• ${fileBasename} - the current opened file's basename
• ${fileBasenameNoExtension} - the current opened file's basename with no file extension
• ${fileDirname} - the current opened file's dirname
• ${fileExtname} - the current opened file's extension
• ${cwd} - the current working directory of the active window on launch

Appendix: Editor configuration

If you would like some assistance with writing the JSON files, and your editor of choice has a way to use a language server, you can use the VSCode JSON language server.

It is recommended to include the $schema declaration as in the above examples, but if that isn't present, the following JSON language server configuration is recommened to load the schema from the Internet:

{
  "json": {
    "schemas": [
      { 
        "fileMatch": [ ".vimspector.json" ],
        "url": "https://puremourning.github.io/vimspector/schema/vimspector.schema.json"
      },
      {
        "fileMatch": [ ".gadgets.json", ".gadgets.d/*.json" ],
        "url": "https://puremourning.github.io/vimspector/schema/gadgets.schema.json"
      }
    ]
  }
}

If your language server client of choice happens to be YouCompleteMe, then the following .ycm_extra_conf.py is good enough to get you going, after following the instructions in the lsp-examples repo to get the server set up:

VIMSPECTOR_HOME = '/path/to/vimspector' # TODO: Change this

def Settings( **kwargs ):
  if kwargs[ 'language' ] == 'json':
    return {
      'ls': {
        'json': {
          'schemas': [
            {
              'fileMatch': [ '.vimspector.json' ],
              'url': f'file://{VIMSPECTOR_HOME}/docs/schema/vimspector.schema.json'
            },
            {
              'fileMatch': [ '.gadgets.json', '.gadgets.d/*.json' ],
              'url': f'file://{VIMSPECTOR_HOME}/docs/schema/gadgets.schema.json'
            }
          ]
        }
      }
    }

  return None # Or your existing Settings definition....

This configuration can be adapted to any other LSP-based editor configuration and is provided just as an example.