[vim/vim] Add dockercompose filetype (PR #19200)

jclsn

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Jan 17, 2026, 11:09:57 AMJan 17

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This is needed for the docker-language-server, which is just submitted a fix for in yegappan/lsp

Having a dockercompose filetype would make the language server configuration much easier

let docker_ls =
			\ #{name: 'docker-language-server',
			\   path: 'docker-language-server',
			\   args: ['start', '--stdio'],
			\   filetype: ['dockerfile', 'dockercompose'],
			\   debug: 'v:true'
			\ }

Not sure if this is the right way though. Syntax should stay yaml. Only the extra filetype is needed to not start the server in all yaml files.

You can view, comment on, or merge this pull request online at:

https://github.com/vim/vim/pull/19200

Commit Summary

1c4e6eb Add dockercompose filetype

File Changes

(2 files)

M runtime/filetype.vim (3)
A runtime/ftplugin/dockercompose.vim (42)

Patch Links:

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Christian Brabandt

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Jan 18, 2026, 3:34:40 PMJan 18

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chrisbra left a comment (vim/vim#19200)

so why do we need an extra filetype if the filetype and syntax is effectively yaml?

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jclsn

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Jan 18, 2026, 3:53:19 PMJan 18

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jclsn left a comment (vim/vim#19200)

Because the LSP client starts servers when it detects certain filetypes. If I put 'yaml' as filetype, it would start the language server for all yaml files.

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jclsn

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Jan 18, 2026, 3:57:32 PMJan 18

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@jclsn pushed 1 commit.

916ed30 Add dockercompose filetype

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Christian Brabandt

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Jan 18, 2026, 4:12:18 PMJan 18

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chrisbra left a comment (vim/vim#19200)

Well, I am not sure about this. Just because you want to use a specific language server for a common filetype sounds like a bad excuse to duplicate filetype and syntax plugins.

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jclsn

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Jan 18, 2026, 4:16:52 PMJan 18

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jclsn left a comment (vim/vim#19200)

I admit that it's not easy in this case. The file being a yaml, should also still trigger language servers for yaml as well. I think Neovim solved this by having subtypes for filetypes like yaml.dockercompose. This would need a bigger patch of course.

Another way would be to have the lsp client trigger not only on filetypes, but also filenames.

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Enno

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Jan 19, 2026, 2:59:49 AMJan 19

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Konfekt left a comment (vim/vim#19200)

It's rather Yaml which can be linted by the yaml-language-server with

    workspaceConfig: {
      yaml: {
        "schemas": {
          "https://raw.githubusercontent.com/compose-spec/compose-spec/master/schema/compose-spec.json": [
            "**/*docker-compose*.yaml",
            "**/*docker-compose*.yml",
            "**/compose.yaml",
            "**/compose.yml"
          ],
      }
   }
}

There is in :help 'filetype'

>  doc/options.txt (lines 3872-3877)
	When a dot appears in the value then this separates two filetype
	names, it should therefore not be used for a filetype.  Example:
		/* vim: set filetype=c.doxygen : */ ~
	This will use the "c" filetype first, then the "doxygen" filetype.
	This works both for filetype plugins and for syntax files.  More than
	one dot may appear.

and

au BufNewFile,BufRead docker-compose.yaml,docker-compose.yml set filetype=dockercompose.yaml

with

filetype: ['dockercompose.yaml', 'dockerfile'],

worked, but I found in the end the Yaml LS to understand the YAML file better

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Remy Suen

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Jan 19, 2026, 6:51:11 AMJan 19

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rcjsuen left a comment (vim/vim#19200)

found in the end the Yaml LS to understand the YAML file better

I'm saddened to hear that as the intent is to provide a great experience for editing Compose files. If you have the time, we would appreciate it if you could let us know of any bugs or missing features with the Compose support in the Docker Language Server. Thank you!

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jclsn

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Jan 19, 2026, 7:47:48 AMJan 19

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jclsn left a comment (vim/vim#19200)

@Konfekt Unfortunately your proposal does not work. The language server starts, but thinks the file is a dockerfile for some reason.

This works as intended:

au BufNewFile,BufRead docker-compose.yaml,docker-compose.yml set filetype=dockercompose
au BufNewFile,BufRead docker-compose.yaml,docker-compose.yml set syntax=yaml

let docker_ls =
			\ #{name: 'docker-language-server',
			\   path: 'docker-language-server',
			\   args: ['start', '--stdio'],
			\   filetype: ['dockerfile', 'dockercompose'],
			\ }

@rcjsuen I don't think that this is an issue with the server.

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Remy Suen

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Jan 19, 2026, 8:16:36 AMJan 19

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rcjsuen left a comment (vim/vim#19200)

I don't think that this is an issue with the server, although triggering the dockercompose mode on dockercompose.yaml or yaml.dockercompose, would be a workaround. I am not sure if a server should work around different clients. The right place to implement this would probably be in the client or by making it possible in vim to assign multiple filetypes to a file.

nvim-lsp seems to be able to use a function to send a different filetype to the server.

Unfortunately, the specification doesn't state how to handle these cases to my knowledge. You want to support a generic format like JSON or YAML but you don't want to prematurely activate. We can also see that clients are handling subtypes differently with your example here with Vim doing dockercompose.yaml and Neovim having it be yaml.docker-compose. The specification doesn't talk about subtypes so there is no standardized naming convention from what I can tell.

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jclsn

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Jan 19, 2026, 8:19:34 AMJan 19

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jclsn left a comment (vim/vim#19200)

@rcjsuen Well, it doesn't have to be a concern of the spec. I think the cleanest way would be to add a filetype override in the client. This way it could handle similar cases for other servers as well.

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jclsn

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Jan 19, 2026, 8:22:24 AMJan 19

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Closed #19200.

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Enno

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Jan 19, 2026, 8:48:16 AMJan 19

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Konfekt left a comment (vim/vim#19200)

@rcjsuen I am sorry, I apparently mixed up docker LSs here and it detects it fine. What I now find with lsp when changing to invalid syntax, like a missing final colon is

Error detected while processing function <SNR>412_Output_cb[5]..lsp#handlers#ProcessMessages[32]..lsp#handlers#ProcessNotif[63]..<SNR>413_ProcessDiagNotif[2]..lsp#diag#DiagNotification[71]..lsp#diag#ProcessNewDiags[20]..lsp#diag#DiagsRefresh:
line   93:
E474: Invalid argument

which is maybe rather an issue of the used plug-in, the same @jclsn is referring to and working on integrating with docker-language-server

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Enno

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Jan 19, 2026, 8:52:25 AMJan 19

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Konfekt left a comment (vim/vim#19200)

I'm confused. @jclsn is using 'docker-language-server' which seems to refer to the Go executable available at https://github.com/docker/docker-language-server whereas indeed I was using https://github.com/rcjsuen/dockerfile-language-server installing docker-langserv`.

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Enno

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Jan 19, 2026, 8:56:34 AMJan 19

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Konfekt left a comment (vim/vim#19200)

So with

name: 'docker-langserver',

filetype: ['dockerfile', 'dockercompose'],

path: 'docker-langserver',
args: ['--stdio'],

the docker-compose.yml is not recognized as such but rather docker file despite @jclsn 's suggestion

au BufNewFile,BufRead docker-compose.yaml,docker-compose.yml set filetype=dockercompose
au BufNewFile,BufRead docker-compose.yaml,docker-compose.yml set syntax=yaml

whereas above errors occur with docker-language-server.

In the end, I found the yaml language server with the corresponding spec to work well enough

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jclsn

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Jan 19, 2026, 8:56:53 AMJan 19

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jclsn left a comment (vim/vim#19200)

@chrisbra Would you be cool with adding

au BufNewFile,BufRead docker-compose.yaml,docker-compose.yml set filetype=dockercompose.yaml

to https://github.com/vim/vim/blob/master/runtime/filetype.vim?

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jclsn

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Jan 19, 2026, 9:00:42 AMJan 19

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jclsn left a comment (vim/vim#19200)

@Konfekt I found an easy fix yegappan/lsp#746

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Remy Suen

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Jan 19, 2026, 11:46:37 AMJan 19

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rcjsuen left a comment (vim/vim#19200)

To help clarify:

rcjsuen/dockerfile-language-server is a language server for Dockerfiles and is written in TypeScript, its "binary" is docker-langserver (in hindsight this was named incorrectly and been named dockerfile-langserver)
docker/docker-language-server is a language server for Dockerfiles, Compose files, and Bake files and is written in Go, its binary is docker-language-server