cli: load revset aliases from config file

Aliases are loaded at WorkspaceCommandHelper::new() as it's easier to warn
invalid declarations there. Not all commands use revsets, but many do, so
I think it's okay to always pay the loading cost. Parsing the declaration
part (i.e. a symbol) should be fast anyway.

The nested error message isn't super readable, but seems good enough.

Config syntax to bikeshed:
- naming: [revset-alias] vs [revset-aliases] ?
- function alias will need quotes: 'f(x)' = 'x'

CHANGELOG.md

@@ -45,6 +45,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 * The new revset function `empty()` finds commits modifying no files.
 
+* Added support for revset aliases. New symbols can be configured by
+  `revset-aliases.<name> = <expression>`.
+
 * It is now possible to specify configuration options on the command line
   with the new `--config-toml` global option.
 

docs/revsets.md

@@ -115,6 +115,18 @@ revsets (expressions) as arguments.
   in `x` doesn't exist (e.g. is an unknown branch name.)
 
 
+## Aliases
+
+New symbols can be defined in the config file, by using any combination
+of the predefined symbols/functions and other aliases.
+
+For example:
+```toml
+[revset-aliases]
+'mine' = 'author(martinvonz)'
+```
+
+
 ## Examples
 
 Show the parent(s) of the working-copy commit (like `git log -1 HEAD`):

src/cli_util.rs

@@ -307,7 +307,7 @@ jj init --git-repo=.",
 
     pub fn for_loaded_repo(
         &self,
-        ui: &Ui,
+        ui: &mut Ui,
         workspace: Workspace,
         repo: Arc<ReadonlyRepo>,
     ) -> Result<WorkspaceCommandHelper, CommandError> {
@@ -330,13 +330,14 @@ pub struct WorkspaceCommandHelper {
     settings: UserSettings,
     workspace: Workspace,
     repo: Arc<ReadonlyRepo>,
+    revset_aliases_map: RevsetAliasesMap,
     may_update_working_copy: bool,
     working_copy_shared_with_git: bool,
 }
 
 impl WorkspaceCommandHelper {
     pub fn new(
-        ui: &Ui,
+        ui: &mut Ui,
         workspace: Workspace,
         string_args: Vec<String>,
         global_args: &GlobalArgs,
@@ -360,6 +361,7 @@ impl WorkspaceCommandHelper {
             settings: ui.settings().clone(),
             workspace,
             repo,
+            revset_aliases_map: load_revset_aliases(ui)?,
             may_update_working_copy,
             working_copy_shared_with_git,
         })
@@ -609,8 +611,11 @@ impl WorkspaceCommandHelper {
         &self,
         revision_str: &str,
     ) -> Result<Rc<RevsetExpression>, RevsetParseError> {
-        let aliases_map = RevsetAliasesMap::new(); // TODO: load from settings
-        let expression = revset::parse(revision_str, &aliases_map, Some(&self.revset_context()))?;
+        let expression = revset::parse(
+            revision_str,
+            &self.revset_aliases_map,
+            Some(&self.revset_context()),
+        )?;
         Ok(revset::optimize(expression))
     }
 
@@ -1024,6 +1029,23 @@ fn resolve_single_op_from_store(
     }
 }
 
+fn load_revset_aliases(ui: &mut Ui) -> Result<RevsetAliasesMap, CommandError> {
+    const TABLE_KEY: &str = "revset-aliases";
+    let mut aliases_map = RevsetAliasesMap::new();
+    if let Ok(table) = ui.settings().config().get_table(TABLE_KEY) {
+        for (decl, value) in table.into_iter().sorted_by(|a, b| a.0.cmp(&b.0)) {
+            let r = value
+                .into_string()
+                .map_err(|e| e.to_string())
+                .and_then(|v| aliases_map.insert(&decl, v).map_err(|e| e.to_string()));
+            if let Err(s) = r {
+                ui.write_warn(format!("Failed to load \"{TABLE_KEY}.{decl}\": {s}\n"))?;
+            }
+        }
+    }
+    Ok(aliases_map)
+}
+
 pub fn resolve_base_revs(
     workspace_command: &WorkspaceCommandHelper,
     revisions: &[String],

tests/test_revset_output.rs

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use common::TestEnvironment;
+use common::{get_stderr_string, get_stdout_string, TestEnvironment};
 
 pub mod common;
 
@@ -119,3 +119,97 @@ fn test_bad_function_call() {
       = Revset function "whatever" doesn't exist
     "###);
 }
+
+#[test]
+fn test_alias() {
+    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");
+
+    test_env.add_config(
+        br###"
+    [revset-aliases]
+    'my-root' = 'root'
+    'syntax-error' = 'whatever &'
+    'recurse' = 'recurse1'
+    'recurse1' = 'recurse'
+    "###,
+    );
+
+    let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-r", "my-root"]);
+    insta::assert_snapshot!(stdout, @r###"
+    o 000000000000  1970-01-01 00:00:00.000 +00:00 000000000000
+      (no description set)
+    "###);
+
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["log", "-r", "root & syntax-error"]);
+    insta::assert_snapshot!(stderr, @r###"
+    Error: Failed to parse revset:  --> 1:8
+      |
+    1 | root & syntax-error
+      |        ^----------^
+      |
+      = Alias "syntax-error" cannot be expanded
+     --> 1:11
+      |
+    1 | whatever &
+      |           ^---
+      |
+      = expected dag_range_pre_op, range_pre_op, or primary
+    "###);
+
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["log", "-r", "root & recurse"]);
+    insta::assert_snapshot!(stderr, @r###"
+    Error: Failed to parse revset:  --> 1:8
+      |
+    1 | root & recurse
+      |        ^-----^
+      |
+      = Alias "recurse" cannot be expanded
+     --> 1:1
+      |
+    1 | recurse1
+      | ^------^
+      |
+      = Alias "recurse1" cannot be expanded
+     --> 1:1
+      |
+    1 | recurse
+      | ^-----^
+      |
+      = Alias "recurse" expanded recursively
+    "###);
+}
+
+#[test]
+fn test_bad_alias_decl() {
+    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");
+
+    test_env.add_config(
+        br###"
+    [revset-aliases]
+    'my-root' = 'root'
+    '"bad"' = 'root'
+    "###,
+    );
+
+    // Invalid declaration should be warned and ignored.
+    let assert = test_env
+        .jj_cmd(&repo_path, &["log", "-r", "my-root"])
+        .assert()
+        .success();
+    insta::assert_snapshot!(get_stdout_string(&assert), @r###"
+    o 000000000000  1970-01-01 00:00:00.000 +00:00 000000000000
+      (no description set)
+    "###);
+    insta::assert_snapshot!(get_stderr_string(&assert), @r###"
+    Failed to load "revset-aliases."bad"":  --> 1:1
+      |
+    1 | "bad"
+      | ^---
+      |
+      = expected identifier
+    "###);
+}