templater: expand similarity hint with aliases

-Tbuiltin now shows the list of the builtin templates, which seems useful.

cli/src/commit_templater.rs

@@ -804,4 +804,5 @@ pub fn parse<'repo>(
     };
     let node = template_parser::parse(template_text, aliases_map)?;
     template_builder::build(&language, &node)
+        .map_err(|err| err.extend_alias_candidates(aliases_map))
 }

cli/src/operation_templater.rs

@@ -255,4 +255,5 @@ pub fn parse(
     };
     let node = template_parser::parse(template_text, aliases_map)?;
     template_builder::build(&language, &node)
+        .map_err(|err| err.extend_alias_candidates(aliases_map))
 }

cli/src/template_parser.rs

@@ -208,6 +208,28 @@ impl TemplateParseError {
         self
     }
 
+    /// If this is a `NoSuchFunction` error, expands the candidates list with
+    /// the given `other_functions`.
+    pub fn extend_function_candidates<I>(mut self, other_functions: I) -> Self
+    where
+        I: IntoIterator,
+        I::Item: AsRef<str>,
+    {
+        if let TemplateParseErrorKind::NoSuchFunction { name, candidates } = &mut self.kind {
+            let other_candidates = collect_similar(name, other_functions);
+            *candidates = itertools::merge(mem::take(candidates), other_candidates)
+                .dedup()
+                .collect();
+        }
+        self
+    }
+
+    /// Expands keyword/function candidates with the given aliases.
+    pub fn extend_alias_candidates(self, aliases_map: &TemplateAliasesMap) -> Self {
+        self.extend_keyword_candidates(aliases_map.symbol_aliases.keys())
+            .extend_function_candidates(aliases_map.function_aliases.keys())
+    }
+
     pub fn kind(&self) -> &TemplateParseErrorKind {
         &self.kind
     }

cli/tests/test_templater.rs

@@ -36,6 +36,9 @@ fn test_templater_parse_error() {
     test_env.add_config(
         r###"
     [template-aliases]
+    'conflicting' = ''
+    'shorted()' = ''
+    'cap(x)' = 'x'
     'format_id(id)' = 'id.sort()'
     "###,
     );
@@ -46,7 +49,7 @@ fn test_templater_parse_error() {
       | ^-------^
       |
       = Keyword "conflicts" doesn't exist
-    Hint: Did you mean "conflict"?
+    Hint: Did you mean "conflict", "conflicting"?
     "###);
     insta::assert_snapshot!(render_err(r#"commit_id.shorter()"#), @r###"
     Error: Failed to parse template:  --> 1:11
@@ -64,6 +67,7 @@ fn test_templater_parse_error() {
       | ^-^
       |
       = Function "cat" doesn't exist
+    Hint: Did you mean "cap"?
     "###);
     insta::assert_snapshot!(render_err(r#""".lines().map(|s| se)"#), @r###"
     Error: Failed to parse template:  --> 1:20
@@ -89,6 +93,18 @@ fn test_templater_parse_error() {
       = Method "sort" doesn't exist for type "CommitOrChangeId"
     Hint: Did you mean "short", "shortest"?
     "###);
+
+    // -Tbuiltin shows the predefined builtin_* aliases. This isn't 100%
+    // guaranteed, but is nice.
+    insta::assert_snapshot!(render_err(r#"builtin"#), @r###"
+    Error: Failed to parse template:  --> 1:1
+      |
+    1 | builtin
+      | ^-----^
+      |
+      = Keyword "builtin" doesn't exist
+    Hint: Did you mean "builtin_change_id_with_hidden_and_divergent_info", "builtin_log_comfortable", "builtin_log_compact", "builtin_log_detailed", "builtin_log_oneline", "builtin_op_log_comfortable", "builtin_op_log_compact"?
+    "###);
 }
 
 #[test]