commit_templater: add an AnyMap for extensions to cache their own info

cli/examples/custom-commit-templater/main.rs

@@ -17,19 +17,22 @@ use jj_cli::commit_templater::{CommitTemplateBuildFnTable, CommitTemplateLanguag
 use jj_cli::template_builder::TemplateLanguage;
 use jj_cli::template_parser::{self, TemplateParseError};
 use jj_cli::templater::{TemplateFunction, TemplatePropertyError};
+use jj_lib::backend::CommitId;
 use jj_lib::commit::Commit;
 use jj_lib::object_id::ObjectId;
+use jj_lib::repo::Repo;
+use jj_lib::revset::RevsetExpression;
 
 struct HexCounter;
 
-fn num_digits_in_id(commit: Commit) -> Result<i64, TemplatePropertyError> {
+fn num_digits_in_id(id: &CommitId) -> i64 {
     let mut count = 0;
-    for ch in commit.id().hex().chars() {
+    for ch in id.hex().chars() {
         if ch.is_ascii_digit() {
             count += 1;
         }
     }
-    Ok(count)
+    count
 }
 
 fn num_char_in_id(commit: Commit, ch_match: char) -> Result<i64, TemplatePropertyError> {
@@ -42,14 +45,54 @@ fn num_char_in_id(commit: Commit, ch_match: char) -> Result<i64, TemplatePropert
     Ok(count)
 }
 
+#[derive(Default)]
+struct MostDigitsInId {
+    count: i64,
+}
+
+impl MostDigitsInId {
+    fn new(repo: &dyn Repo) -> Self {
+        let count = RevsetExpression::all()
+            .evaluate_programmatic(repo)
+            .unwrap()
+            .iter()
+            .map(|id| num_digits_in_id(&id))
+            .max()
+            .unwrap_or(0);
+        Self { count }
+    }
+
+    fn count(&self) -> i64 {
+        self.count
+    }
+}
+
 impl CommitTemplateLanguageExtension for HexCounter {
     fn build_fn_table<'repo>(&self) -> CommitTemplateBuildFnTable<'repo> {
         let mut table = CommitTemplateBuildFnTable::empty();
+        table.commit_methods.insert(
+            "has_most_digits",
+            |language, _build_context, property, call| {
+                template_parser::expect_no_arguments(call)?;
+                let most_digits = language
+                    .cache_extension(|| MostDigitsInId::new(language.repo()))
+                    .count();
+                Ok(
+                    language.wrap_boolean(TemplateFunction::new(property, move |commit| {
+                        Ok(num_digits_in_id(commit.id()) == most_digits)
+                    })),
+                )
+            },
+        );
         table.commit_methods.insert(
             "num_digits_in_id",
             |language, _build_context, property, call| {
                 template_parser::expect_no_arguments(call)?;
-                Ok(language.wrap_integer(TemplateFunction::new(property, num_digits_in_id)))
+                Ok(
+                    language.wrap_integer(TemplateFunction::new(property, |commit| {
+                        Ok(num_digits_in_id(commit.id()))
+                    })),
+                )
             },
         );
         table.commit_methods.insert(

cli/src/commit_templater.rs

@@ -12,12 +12,14 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+use std::any::Any;
 use std::cmp::max;
 use std::collections::HashMap;
 use std::io;
 use std::rc::Rc;
 
 use itertools::Itertools as _;
+use jj_lib::any_map::AnyMap;
 use jj_lib::backend::{ChangeId, CommitId};
 use jj_lib::commit::Commit;
 use jj_lib::hex_util::to_reverse_hex;
@@ -50,6 +52,7 @@ pub struct CommitTemplateLanguage<'repo> {
     id_prefix_context: &'repo IdPrefixContext,
     build_fn_table: CommitTemplateBuildFnTable<'repo>,
     keyword_cache: CommitKeywordCache,
+    cache_extensions: AnyMap,
 }
 
 impl<'repo> CommitTemplateLanguage<'repo> {
@@ -71,6 +74,7 @@ impl<'repo> CommitTemplateLanguage<'repo> {
             id_prefix_context,
             build_fn_table,
             keyword_cache: CommitKeywordCache::default(),
+            cache_extensions: AnyMap::new(),
         }
     }
 }
@@ -156,6 +160,10 @@ impl<'repo> CommitTemplateLanguage<'repo> {
         &self.keyword_cache
     }
 
+    pub fn cache_extension<T: Any>(&self, generator: impl FnOnce() -> T) -> &T {
+        self.cache_extensions.insert(generator)
+    }
+
     pub fn wrap_commit(
         &self,
         property: impl TemplateProperty<Commit, Output = Commit> + 'repo,