templater: fix parsing of parenthesized expression

A "list" is a sequence of more than one "term" nodes, so it shouldn't contain
a single parenthesized node.

Also, a parenthesized "term" rule wasn't handled.

src/template.pest

@@ -32,7 +32,7 @@ maybe_method = { ("." ~ function)* }
 
 // Note that "x(y)" is a function call but "x (y)" concatenates "x" and "y"
 term = {
-  ("(" ~ term ~ ")") ~ maybe_method
+  ("(" ~ template ~ ")") ~ maybe_method
   | function ~ maybe_method
   | identifier ~ maybe_method
   | literal ~ maybe_method
@@ -40,8 +40,7 @@ term = {
 }
 
 list = {
-  ("(" ~ list ~ ")")
-  | term ~ (whitespace+ ~ term)+
+  term ~ (whitespace+ ~ term)+
 }
 
 template = {

src/template_parser.rs

@@ -349,6 +349,7 @@ fn parse_commit_term<'a>(
                     name => panic!("function {name} not implemented"),
                 }
             }
+            Rule::template => parse_commit_template_rule(repo, workspace_id, expr),
             other => panic!("unexpected term: {other:?}"),
         }
     }

tests/test_templater.rs

@@ -76,3 +76,30 @@ fn test_templater_branches() {
     o 000000000000 
     "###);
 }
+
+#[test]
+fn test_templater_parsed_tree() {
+    let test_env = TestEnvironment::default();
+    test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
+    let repo_path = test_env.env_root().join("repo");
+
+    // Parenthesized single term
+    let stdout = test_env.jj_cmd_success(
+        &repo_path,
+        &["log", "--no-graph", "-r@-", "-T", r#"(commit_id.short())"#],
+    );
+    insta::assert_snapshot!(stdout, @"000000000000");
+
+    // Parenthesized multiple terms and concatenation
+    let stdout = test_env.jj_cmd_success(
+        &repo_path,
+        &[
+            "log",
+            "--no-graph",
+            "-r@-",
+            "-T",
+            r#"(commit_id.short() " ") empty"#,
+        ],
+    );
+    insta::assert_snapshot!(stdout, @"000000000000 true");
+}