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Vim Kuberetes YAML Support

Do you write YAML manifests for Kubernetes in vim? Have you also spent countless time determining where in the spec a field belongs? Or perhaps you want a quick reminder about the difference between args and command? Good news! You can easily link vim to the yaml-language-server to get completion, validation and more. In this post we’ll explore how to setup a language server client to take advantage of this.

Click here to watch the video version of this content.

Language Server

Language servers provide programming language features to editors and IDEs by allowing communication over the Language Server Protocol (LSP). This approach is exciting because it enables 1 implementation to feed a multitude of editors and IDEs. I previously did a post on gopls the golang language server and how it can also be used in vim. For Kubernetes YAML completion the flow is similar.

For vim to operate as described, you need a language server client. The two ways I am aware of are LanguageClient-neovim and coc.vim. In this post, I’ll be showing the coc.vim plugin as it is the most popular plugin at the time of this writing. You can install coc.vim using vim-plug.

" Use release branch (Recommend)
Plug 'neoclide/coc.nvim', {'branch': 'release'}

" Or build from source code by use yarn: https://yarnpkg.com
Plug 'neoclide/coc.nvim', {'do': 'yarn install --frozen-lockfile'}

To run coc (and eventually the yaml-language-server), you need node.js installed.

curl -sL install-node.now.sh/lts | bash

With coc.vim setup, install the coc-yaml server extension from within vim.

:CocInstall coc-yaml

Lastly, you’ll likely want to start with the coc-vim config mappings found in the example configuration. These enable things like ctrl + space to trigger autocompletion.

Configure yaml-language-server Detection

In order for coc to use the yaml-language-server, you must tell it to load the Kubernetes schema when editing YAML files. You can do this by modifying the coc-config.

:CocConfig

In the config file, add kubernetes for all yaml files. Below you can see my configuration, which includes a golang configuration.

{
  "languageserver": {
      "golang": {
        "command": "gopls",
        "rootPatterns": ["go.mod"],
        "filetypes": ["go"]
      }
  },

  "yaml.schemas": {
      "kubernetes": "/*.yaml"
  }

}

kubernetes is a reserved field that tells the language server to load the Kubernetes schema URL from this constant variable. yaml.schemas can be expanded to add support for other schemas, check out the schema association docs for more details.

Now you can create a YAML file and start using the autocompletion. Based on your context, hitting ctrl + space (or your equivalent vim binding) should bring up available fields and documentation.

ctrl + space works here because I have set inoremap <silent><expr> <c-space> coc#refresh(), if you haven’t, visit the coc.nvim README for an example configuration.

Set Kubernetes API Version

At the time of this writing, yaml-language-server ships with the Kubernetes 1.14.0 schemas. I’m unaware of a way to dynamically choose the schema, although I have opened a GitHub issue inquiring about it. Luckily, since the language server is written in typescript, it is fairly easy to modify if you know where the server.ts file lives.

To determine where it is installed on your machine, simply open up a YAML file with vim and check your processes for yaml-language-server.

ps aux | grep -i yaml-language-server

joshrosso         2380  45.9  0.2  5586084  69324   ??  S     9:32PM   0:00.43 /usr/local/Cellar/node/13.5.0/bin/node /Users/joshrosso/.config/coc/extensions/node_modules/coc-yaml/node_modules/yaml-language-server/out/server/src/server.js --node-ipc --node-ipc --clientProcessId=2379
joshrosso         2382   0.0  0.0  4399352    788 s001  S+    9:32PM   0:00.00 grep -i yaml-language-server

The above process, 2380, is only active because an instance of vim is editing a YAML file.

As you can see, mine is located at /Users/joshrosso/.config/coc/extensions/node_modules/coc-yaml/node_modules/yaml-language-server/out/server/src/server.js. You can edit the file and update the KUBERNETES_SCHEMA_URL variable to, for example, 1.17.0.

// old 1.14.0 schema
//exports.KUBERNETES_SCHEMA_URL = "https://raw.githubusercontent.com/garethr/kubernetes-json-schema/master/v1.14.0-standalone-strict/all.json";
// new 1.17.0 schema in instrumenta repo
exports.KUBERNETES_SCHEMA_URL = "https://raw.githubusercontent.com/instrumenta/kubernetes-json-schema/master/v1.17.0-standalone-strict/all.json";

Depending on your version of coc-yaml, the variable's location may vary. Do note that I have changed the repo from garethr to instrumenta. It appears garethr has started maintaining the schemas in that repo.

As a test, you can validate a field shows up that wasn’t previously available. For me, I can check for startupProbe, which wasn’t available in the 1.14 schema.

Summary

I hope you’re as stoked about this feature set as me! Happy YAMLing :). Be sure to checkout the following repos for a deeper dive into the tools used in this post.

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