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template: add env() function #9084

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406c41c
template: add `env()` function
chawyehsu Mar 11, 2026
45bbcbd
templater: provide environment variables accessing in template languages
chawyehsu Mar 13, 2026
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template: add env() function 
Signed-off-by: Chawye Hsu <su+git@chawyehsu.com>
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@chawyehsu
chawyehsu committed Mar 14, 2026
commit 406c41ca4cf592b91e1f1d423fb5fbba826e451c
3 changes: 3 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -29,6 +29,9 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
* [Diff colors](docs/config.md#diff-colors-and-styles) can now be configured
differently for each format.

* Add `env(name)` template function that looks up the value of a given
environment variable.

### Fixed bugs

## [0.39.0] - 2026-03-04
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9 changes: 9 additions & 0 deletions cli/src/template_builder.rs
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Expand Up @@ -2139,6 +2139,15 @@ fn builtin_functions<'a, L: TemplateLanguage<'a> + ?Sized>() -> TemplateBuildFun
// .decorated("", "") to trim leading/trailing whitespace
Ok(Literal(value.map(|v| v.decorated("", ""))).into_dyn_wrapped())
});
map.insert("env", |_language, diagnostics, _build_ctx, function| {
let [var_name_node] = function.expect_exact_arguments()?;
let var_name =
template_parser::catch_aliases(diagnostics, var_name_node, |_diagnostics, node| {
template_parser::expect_string_literal(node)
})?;
let out_property = std::env::var(var_name).unwrap_or_default();
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@yuja yuja Mar 12, 2026

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nit: Can we pass HashMap<String, String> as evaluation context instead? I think it's better to not access std::env::var() in templater. For example, the current working directory is specified by path_converter: &'repo RepoPathUiConverter

Perhaps, we can reuse ConfigEnv::environment.

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@chawyehsu chawyehsu Mar 12, 2026 •
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This is fairly reasonable. I think reusing ConfigEnv's environment would be a good idea for deterministic evaluation, but as of now I definitely need a deeper understanding of jj's codebase to understand how to pass it into the templater's context and use it, considering this is my first contribution. ;p

Ok(Literal(out_property).into_dyn_wrapped())
});
map
}

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22 changes: 22 additions & 0 deletions cli/tests/test_templater.rs
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Expand Up @@ -542,6 +542,28 @@ fn test_templater_config_function() {
insta::assert_snapshot!(render("config('unknown')"), @"");
}

#[test]
fn test_templater_env_function() {
let test_env = TestEnvironment::default();
test_env.run_jj_in(".", ["git", "init", "repo"]).success();
let work_dir = test_env.work_dir("repo");
let render = |template| get_template_output(&work_dir, "@-", template);
insta::assert_snapshot!(render("env('JJ_TEMPLATE_ENV')"), @"");

let output = work_dir.run_jj_with(|cmd| {
cmd.args([
"log",
"--no-graph",
"-r",
"@-",
"-T",
"env('JJ_TEMPLATE_ENV')",
])
.env("JJ_TEMPLATE_ENV", "template-env-value")
});
insta::assert_snapshot!(output, @"template-env-value[EOF]");
}

#[must_use]
fn get_template_output(work_dir: &TestWorkDir, rev: &str, template: &str) -> CommandOutput {
work_dir.run_jj(["log", "--no-graph", "-r", rev, "-T", template])
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2 changes: 2 additions & 0 deletions docs/templates.md
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Expand Up @@ -122,6 +122,8 @@ The following functions are defined.
* `git_web_url([remote: String]) -> String`: Best-effort conversion of a git
remote URL to an HTTPS web URL. Defaults to the "origin" remote. Returns an
empty string on failure. SSH host alias resolution is currently unsupported.
* `env(name: StringLiteral) -> String`:
Look up the value of a given environment variable by `name`.

## Types

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