Support CUE lang as an alternate templating method.

[jakeswenson]

This idea would require some flushing out. The current text templates are work for simple templates but mixing template languages inside other configuration languages can become unwieldy and painful to maintain.

Instead I'm wondering if it would be nice to support cue lang templates as well.

Cue Lang is a super powerful configuration language that has a solid well defined type system and can "eval"/generate into many configuration outputs (JSON, YAML, TOML, etc...)

it would be really nice to be able to create .cue template files that can be used as an alternate (cleaner?) way to build complex templates...

Thoughts on this? I could work to put some examples together to help firm it up, but this could obviously turn into a significant chunk of work to figure out how to expose all the current template functions to cue...

[jakeswenson]

I was able to scrap something together without proper first class integration from chezmoi using the output template function.

Here is the setup for this proof of concept:

.chezmoitemplates/cue

{{- output "cue" "export"
	(joinPath .chezmoi.sourceDir ".chezmoi.types.cue")
	(joinPath .chezmoi.sourceDir (print .chezmoi.sourceFile ".cue"))
	"-t" (. | toJson | print "data=")
-}}

dot_claude/settings.json.tmpl

{{- template "cue" . -}}

dot_claude/settings.json.tmpl.cue

package dotfiles

"$schema":               "https://json.schemastore.org/claude-code-settings.json"
"includeCoAuthoredBy":   false
"alwaysThinkingEnabled": true

"feedbackSurveyState": {
	"lastShownTime": 1754284490018
}

_work_config: {
	"env": {
		"ANTHROPIC_BEDROCK_BASE_URL":    "https://..."
		"ANTHROPIC_AUTH_TOKEN":          #cz.ai.claude_key
		"CLAUDE_CODE_USE_BEDROCK":       "1"
	}

	"model": "opus"
}

if #cz.is_work {_work_config}

.chezmoit.types.cue

This file defines my chezmoi configuration data and JSON parses what is supplied by the output template function.

package dotfiles

import "encoding/json"

#ConfigSchemaAndDefaults: {
	ai: claude_key: string | *""
	is_work: bool | *false
	...
}

_#data_str: string @tag(data)

#cz: #ConfigSchemaAndDefaults & json.Unmarshal(_#data_str)

Testing It

❯ cz cat ~/.claude/settings.json
{
    "$schema": "https://json.schemastore.org/claude-code-settings.json",
    "includeCoAuthoredBy": false,
    "alwaysThinkingEnabled": true,
    "feedbackSurveyState": {
        "lastShownTime": 1754284490018
    }
}

and when is_work is true, then:

{
    "$schema": "https://json.schemastore.org/claude-code-settings.json",
    "includeCoAuthoredBy": false,
    "alwaysThinkingEnabled": true,
    "feedbackSurveyState": {
        "lastShownTime": 1754284490018
    },
    "env": {
        "ANTHROPIC_BEDROCK_BASE_URL": "https://...",
        "ANTHROPIC_AUTH_TOKEN": "myKey",
        "CLAUDE_CODE_USE_BEDROCK": "1"
    },
    "model": "opus"
}

To me this was a huge success. I find the cue file significantly easier to read over go template expressions in a json file ({{ if }}...{{end}})

Thanks for your time

[twpayne]

This looks like a good solution.

I'm a fan of CUE, but it is for generating structured data only. You can't use CUE to generate arbitrary files like git configs or shell scripts.

[jakeswenson]

Agree, it would be nice to have it as a native alternative option to .tmpl text templates, specifically for use templating structured configs (toml, json, yaml, etc.)

Nowadays so many tools have structured config files. It would be nice if cue as a library was included in the chezmoi binary (similar to how age was partially included) so that it was one less dependency to install...

regarding git configs (ini) i wonder if {{- template "cue" . | fromJson | toIni -}} works... Anyways I'm not asking to remove text templates, only to instead supply a better option to treating everything as strings.

[halostatue]

Note that .gitconfig looks like an ini-file but it really isn't.

[twpayne]

@jakeswenson What exactly would adding CUE templating support to chezmoi look like?

CUE is written in Go and available as a library, so including the CUE code in chezmoi is possible. What's missing is the user experience. Note that, with CUE, the final generated structured config (in JSON or YAML or whatever) is usually the result of combining multiple .cue files.

What I'm looking for is some statement along the lines of "if I have a file called A in my chezmoi source directory containing B, then chezmoi will generate a file called X containing Y in my target directory". Could you provide values for A, B, X, and Y?