cli: add "config list --template" support

There's a caveat: "jj config list -Tname" will concatenate all names in a
single line. That's correct but useless. We might want some option or config
knob to complete missing "\n". This also applies to "log --no-graph".

CHANGELOG.md

@@ -46,6 +46,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * `jj show` now accepts `-T`/`--template` option to render its output using
   template
 
+* `jj config list` now accepts `-T`/`--template` option.
+
 * `jj git fetch` now accepts `-b` as a shorthand for `--branch`, making it more
   consistent with other commands that accept a branch
 

cli/src/commands/config.rs

@@ -24,6 +24,9 @@ use crate::cli_util::{
 };
 use crate::command_error::{user_error, CommandError};
 use crate::config::{AnnotatedValue, ConfigSource};
+use crate::generic_templater::GenericTemplateLanguage;
+use crate::template_builder::TemplateLanguage as _;
+use crate::templater::TemplatePropertyFn;
 use crate::ui::Ui;
 
 #[derive(clap::Args, Clone, Debug)]
@@ -92,6 +95,17 @@ pub(crate) struct ConfigListArgs {
     #[arg(long)]
     repo: bool,
     // TODO(#1047): Support --show-origin using LayeredConfigs.
+    /// Render each variable using the given template
+    ///
+    /// The following keywords are defined:
+    ///
+    /// * `name: String`: Config name.
+    /// * `value: String`: Serialized value in TOML syntax.
+    /// * `overridden: Boolean`: True if the value is shadowed by other.
+    ///
+    /// For the syntax, see https://github.com/martinvonz/jj/blob/main/docs/templates.md
+    #[arg(long, short = 'T', verbatim_doc_comment)]
+    template: Option<String>,
 }
 
 impl ConfigListArgs {
@@ -170,50 +184,74 @@ pub(crate) fn cmd_config(
     }
 }
 
+fn config_template_language() -> GenericTemplateLanguage<'static, AnnotatedValue> {
+    fn prop_fn<R, F: Fn(&AnnotatedValue) -> R>(f: F) -> TemplatePropertyFn<F> {
+        TemplatePropertyFn(f)
+    }
+    let mut language = GenericTemplateLanguage::new();
+    // "name" instead of "path" to avoid confusion with the source file path
+    language.add_keyword("name", |language| {
+        let property = prop_fn(|annotated| Ok(annotated.path.join(".")));
+        Ok(language.wrap_string(property))
+    });
+    language.add_keyword("value", |language| {
+        // TODO: would be nice if we can provide raw dynamically-typed value
+        let property = prop_fn(|annotated| Ok(serialize_config_value(&annotated.value)));
+        Ok(language.wrap_string(property))
+    });
+    language.add_keyword("overridden", |language| {
+        let property = prop_fn(|annotated| Ok(annotated.is_overridden));
+        Ok(language.wrap_boolean(property))
+    });
+    language
+}
+
 #[instrument(skip_all)]
 pub(crate) fn cmd_config_list(
     ui: &mut Ui,
     command: &CommandHelper,
     args: &ConfigListArgs,
 ) -> Result<(), CommandError> {
+    let template = {
+        let language = config_template_language();
+        let text = match &args.template {
+            Some(value) => value.to_owned(),
+            None => command
+                .settings()
+                .config()
+                .get_string("templates.config_list")?,
+        };
+        command.parse_template(ui, &language, &text)?
+    };
+
     ui.request_pager();
+    let mut formatter = ui.stdout_formatter();
     let name_path = args
         .name
         .as_ref()
         .map_or(vec![], |name| name.split('.').collect_vec());
-    let values = command.resolved_config_values(&name_path)?;
     let mut wrote_values = false;
-    for AnnotatedValue {
-        path,
-        value,
-        source,
-        is_overridden,
-    } in &values
-    {
+    for annotated in command.resolved_config_values(&name_path)? {
         // Remove overridden values.
-        if *is_overridden && !args.include_overridden {
+        if annotated.is_overridden && !args.include_overridden {
             continue;
         }
 
         if let Some(target_source) = args.get_source_kind() {
-            if target_source != *source {
+            if target_source != annotated.source {
                 continue;
             }
         }
 
         // Skip built-ins if not included.
-        if !args.include_defaults && *source == ConfigSource::Default {
+        if !args.include_defaults && annotated.source == ConfigSource::Default {
             continue;
         }
-        writeln!(
-            ui.stdout(),
-            "{}{}={}",
-            if *is_overridden { "# " } else { "" },
-            path.join("."),
-            serialize_config_value(value)
-        )?;
+
+        template.format(&annotated, formatter.as_mut())?;
         wrote_values = true;
     }
+    drop(formatter);
     if !wrote_values {
         // Note to stderr explaining why output is empty.
         if let Some(name) = &args.name {

cli/src/config/templates.toml

@@ -24,6 +24,15 @@ separate(" ",
 )
 '''
 
+config_list = '''
+concat(
+  if(overridden, "# "),
+  name,
+  "=",
+  value,
+) ++ "\n"
+'''
+
 log = 'builtin_log_compact'
 op_log = 'builtin_op_log_compact'
 show = 'builtin_log_detailed'

cli/tests/cli-reference@.md.snap

@@ -489,6 +489,7 @@ List variables set in config file, along with their values
 
   Possible values: `true`, `false`
 
+* `-T`, `--template <TEMPLATE>` — Render each variable using the given template
 
 
 

cli/tests/test_config_command.rs

@@ -35,6 +35,14 @@ fn test_config_list_single() {
     insta::assert_snapshot!(stdout, @r###"
     test-table.somekey="some value"
     "###);
+
+    let stdout = test_env.jj_cmd_success(
+        test_env.env_root(),
+        &["config", "list", r#"-Tname ++ "\n""#, "test-table.somekey"],
+    );
+    insta::assert_snapshot!(stdout, @r###"
+    test-table.somekey
+    "###);
 }
 
 #[test]
@@ -114,6 +122,7 @@ fn test_config_list_all() {
     y.bar = 123
     "#,
     );
+
     let stdout = test_env.jj_cmd_success(test_env.env_root(), &["config", "list"]);
     insta::assert_snapshot!(
         find_stdout_lines(r"(test-val|test-table\b[^=]*)", &stdout),