templater: port annotation line content to template

I originally thought we would have to add BString template type first, but we
can use opaque Template type instead.

CHANGELOG.md

@@ -63,7 +63,8 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
   using `templates.backout_description`.
 
 * New `AnnotationLine` templater type. Used in `templates.file_annotate`.
-  Provides `self.commit()`, `self.line_number()`, and `self.first_line_in_hunk()`.
+  Provides `self.commit()`, `.content()`, `.line_number()`, and
+  `.first_line_in_hunk()`.
 
 ### Fixed bugs
 

cli/src/commands/file/annotate.rs

@@ -50,13 +50,13 @@ pub(crate) struct FileAnnotateArgs {
         add = ArgValueCandidates::new(complete::all_revisions)
     )]
     revision: Option<RevisionArg>,
-    /// Render a prefix for each line using the given template
+    /// Render each line using the given template
     ///
     /// All 0-argument methods of the [`AnnotationLine` type] are available as
     /// keywords in the [template expression].
     ///
-    /// If not specified, this defaults to the
-    /// `templates.file_annotate` setting.
+    /// If not specified, this defaults to the `templates.file_annotate`
+    /// setting.
     ///
     /// [template expression]:
     ///     https://jj-vcs.github.io/jj/latest/templates/
@@ -123,17 +123,17 @@ fn render_file_annotation(
     ui.request_pager();
     let mut formatter = ui.stdout_formatter();
     let mut last_id = None;
-    for (line_number, (commit_id, line)) in annotation.lines().enumerate() {
+    for (line_number, (commit_id, content)) in annotation.lines().enumerate() {
         let commit_id = commit_id.expect("should reached to the empty ancestor");
         let commit = repo.store().get_commit(commit_id)?;
         let first_line_in_hunk = last_id != Some(commit_id);
         let annotation_line = AnnotationLine {
             commit,
+            content: content.to_owned(),
             line_number: line_number + 1,
             first_line_in_hunk,
         };
         template_render.format(&annotation_line, formatter.as_mut())?;
-        formatter.write_all(line)?;
         last_id = Some(commit_id);
     }
 

cli/src/commit_templater.rs

@@ -19,6 +19,7 @@ use std::collections::HashMap;
 use std::io;
 use std::rc::Rc;
 
+use bstr::BString;
 use futures::stream::BoxStream;
 use futures::StreamExt as _;
 use futures::TryStreamExt as _;
@@ -2218,10 +2219,10 @@ pub fn builtin_cryptographic_signature_methods<'repo>(
     map
 }
 
-// TODO: add `line: BString` field when available in template language
 #[derive(Debug, Clone)]
 pub struct AnnotationLine {
     pub commit: Commit,
+    pub content: BString,
     pub line_number: usize,
     pub first_line_in_hunk: bool,
 }
@@ -2238,6 +2239,15 @@ pub fn builtin_annotation_line_methods<'repo>(
             Ok(L::wrap_commit(out_property))
         },
     );
+    map.insert(
+        "content",
+        |_language, _diagnostics, _build_ctx, self_property, function| {
+            function.expect_no_arguments()?;
+            let out_property = self_property.map(|line| line.content);
+            // TODO: Add Bytes or BString template type?
+            Ok(L::wrap_template(out_property.into_template()))
+        },
+    );
     map.insert(
         "line_number",
         |_language, _diagnostics, _build_ctx, self_property, function| {

cli/src/config/templates.toml

@@ -27,8 +27,8 @@ separate(" ",
   commit.change_id().shortest(8),
   pad_end(8, truncate_end(8, commit.author().email().local())),
   commit_timestamp(commit).local().format('%Y-%m-%d %H:%M:%S'),
-  pad_start(4, line_number) ++ ": ",
-)
+  pad_start(4, line_number),
+) ++ ": " ++ content
 '''
 
 config_list = '''

cli/src/templater.rs

@@ -20,6 +20,8 @@ use std::io::Write;
 use std::iter;
 use std::rc::Rc;
 
+use bstr::BStr;
+use bstr::BString;
 use jj_lib::backend::Signature;
 use jj_lib::backend::Timestamp;
 use jj_lib::config::ConfigValue;
@@ -69,6 +71,18 @@ impl<T: Template> Template for Option<T> {
     }
 }
 
+impl Template for BString {
+    fn format(&self, formatter: &mut TemplateFormatter) -> io::Result<()> {
+        formatter.as_mut().write_all(self)
+    }
+}
+
+impl Template for &BStr {
+    fn format(&self, formatter: &mut TemplateFormatter) -> io::Result<()> {
+        formatter.as_mut().write_all(self)
+    }
+}
+
 impl Template for ConfigValue {
     fn format(&self, formatter: &mut TemplateFormatter) -> io::Result<()> {
         write!(formatter, "{self}")

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

@@ -898,7 +898,7 @@ Annotates a revision line by line. Each line includes the source change that int
 ###### **Options:**
 
 * `-r`, `--revision <REVSET>` — an optional revision to start at
-* `-T`, `--template <TEMPLATE>` — Render a prefix for each line using the given template
+* `-T`, `--template <TEMPLATE>` — Render each line using the given template
 
    All 0-argument methods of the [`AnnotationLine` type] are available as keywords in the [template expression].
 

cli/tests/test_file_annotate_command.rs

@@ -179,7 +179,7 @@ fn test_annotate_with_template() {
         commit_timestamp(commit).local().format('%Y-%m-%d %H:%M:%S')
             ++ " "
             ++ commit.author(),
-    ) ++ "\n") ++ pad_start(4, line_number) ++ ": "
+    ) ++ "\n") ++ pad_start(4, line_number) ++ ": " ++ content
     "#};
 
     let stdout = test_env.jj_cmd_success(

docs/templates.md

@@ -95,6 +95,7 @@ The following functions are defined.
 The following methods are defined.
 
 * `.commit() -> Commit`: Commit responsible for changing the relevant line.
+* `.content() -> Template`: Line content including newline character.
 * `.line_number() -> Integer`: 1-based line number.
 * `.first_line_in_hunk() -> Boolean`: False when the directly preceding line
   references the same commit.