MCP access part 5: Claude desktop config parser

[greedy52]

Related:

• Teleport MCP access MVP #54705

Doing a small separate PR for parser so it can be shared for tsh mcp db

[zmb3]

I'm having a hard time understanding what the 2-phase unmarshal is doing here.

[greedy52]

once for known fields and once for unknown fields. it's quite awkward to do this in golang. i didn't find a good way to do this.

I will try out json patch

[Tener]

I think the current code is idiomatic enough, but a comment would be most welcome.

[greedy52]

I looked into json patch but it doesn't work very well. as suggested by @Tener , i switched to https://github.com/tidwall/sjson

let me know what you think about the latest changes.

one problem i have with sjson is the formatting so i decided to apply some extra formatting when saving. not sure if i went a little too far. Since this is a config edited by human most of the time, i imagine you want it to be prettified by default.

[juliaogris]

You have probably seen this SO post https://stackoverflow.com/a/33437853

I think my mental model would be to use AdditionalFields, not AllFields, but you might have good reasons for doing this that I don't understand.

[Tener]

As noted I think we should try very hard to not reformat the config. I suggested one possible solution.

[Tener]

I think the current code is idiomatic enough, but a comment would be most welcome.

[gabrielcorado]

suggestion/nit: Place those behind a struct (maybe we can init it with the config path) so we can rely on an interface on the caller side. It would be easier to add and test other configurations.

What I would expect to use from the caller:

type ConfigFormat interface {
    LoadConfig(configPath string) (Config, error)
    
    // Just for generating the config in the specific format.
    EmptyConfig() Config
    // or...
    GenerateConfig(serverName string, server MCPServer) ([]byte, error)
}

type Config interface {
    PutMCPServer() error
    RemoveMCPServer() error
    Save() error
    Generate() ([]byte, error)
}

I know that implies having shared structs for MCPServer. For the initial version, we could provide the necessary functions to generate a minimal configuration (without loading or updating any file).

[greedy52]

caller side can do this if it needs to. also the config and parsing is simple enough so i would probably just write a file in t.Temp() to when testing caller