Extensions registering tasks (#9572)

This PR also introduces built-in tasks for Rust and Elixir. Note that
this is not a precedent for future PRs to include tasks for more
languages; we simply want to find the rough edges with tasks & language
integrations before proceeding to task contexts provided by extensions.

As is, we'll load tasks for all loaded languages, so in order to get
Elixir tasks, you have to open an Elixir buffer first. I think it sort
of makes sense (though it's not ideal), as in the future where
extensions do provide their own tasks.json, we'd like to limit the # of
tasks surfaced to the user to make them as relevant to the project at
hand as possible.

Release Notes:

- Added built-in tasks for Rust and Elixir files.

crates/tasks_ui/src/lib.rs

@@ -1,11 +1,11 @@
-use std::{collections::HashMap, path::PathBuf};
+use std::path::PathBuf;
 
 use editor::Editor;
 use gpui::{AppContext, ViewContext, WindowContext};
 use language::Point;
 use modal::{Spawn, TasksModal};
 use project::{Location, WorktreeId};
-use task::{Task, TaskContext};
+use task::{Task, TaskContext, TaskVariables};
 use util::ResultExt;
 use workspace::Workspace;
 
@@ -156,40 +156,37 @@ fn task_context(
 
                 let selected_text = buffer.read(cx).chars_for_range(selection_range).collect();
 
-                let mut env = HashMap::from_iter([
+                let mut task_variables = TaskVariables::from_iter([
                     ("ZED_ROW".into(), row.to_string()),
                     ("ZED_COLUMN".into(), column.to_string()),
                     ("ZED_SELECTED_TEXT".into(), selected_text),
                 ]);
                 if let Some(path) = current_file {
-                    env.insert("ZED_FILE".into(), path);
+                    task_variables.0.insert("ZED_FILE".into(), path);
                 }
                 if let Some(worktree_path) = worktree_path {
-                    env.insert("ZED_WORKTREE_ROOT".into(), worktree_path);
+                    task_variables
+                        .0
+                        .insert("ZED_WORKTREE_ROOT".into(), worktree_path);
                 }
                 if let Some(language_context) = context {
-                    if let Some(symbol) = language_context.symbol {
-                        env.insert("ZED_SYMBOL".into(), symbol);
-                    }
-                    if let Some(symbol) = language_context.package {
-                        env.insert("ZED_PACKAGE".into(), symbol);
-                    }
+                    task_variables.0.extend(language_context.0);
                 }
 
                 Some(TaskContext {
                     cwd: cwd.clone(),
-                    env,
+                    task_variables,
                 })
             })
         })()
         .unwrap_or_else(|| TaskContext {
             cwd,
-            env: Default::default(),
+            task_variables: Default::default(),
         })
     } else {
         TaskContext {
             cwd,
-            env: Default::default(),
+            task_variables: Default::default(),
         }
     }
 }
@@ -248,14 +245,14 @@ fn task_cwd(workspace: &Workspace, cx: &mut WindowContext) -> anyhow::Result<Opt
 
 #[cfg(test)]
 mod tests {
-    use std::{collections::HashMap, sync::Arc};
+    use std::sync::Arc;
 
     use editor::Editor;
     use gpui::{Entity, TestAppContext};
-    use language::{DefaultContextProvider, Language, LanguageConfig};
+    use language::{Language, LanguageConfig, SymbolContextProvider};
     use project::{FakeFs, Project, TaskSourceKind};
     use serde_json::json;
-    use task::{oneshot_source::OneshotSource, TaskContext};
+    use task::{oneshot_source::OneshotSource, TaskContext, TaskVariables};
     use ui::VisualContext;
     use workspace::{AppState, Workspace};
 
@@ -302,7 +299,7 @@ mod tests {
             name: (_) @name) @item"#,
             )
             .unwrap()
-            .with_context_provider(Some(Arc::new(DefaultContextProvider))),
+            .with_context_provider(Some(Arc::new(SymbolContextProvider))),
         );
 
         let typescript_language = Arc::new(
@@ -320,7 +317,7 @@ mod tests {
                       ")" @context)) @item"#,
             )
             .unwrap()
-            .with_context_provider(Some(Arc::new(DefaultContextProvider))),
+            .with_context_provider(Some(Arc::new(SymbolContextProvider))),
         );
         let project = Project::test(fs, ["/dir".as_ref()], cx).await;
         project.update(cx, |project, cx| {
@@ -362,7 +359,7 @@ mod tests {
                 task_context(this, task_cwd(this, cx).unwrap(), cx),
                 TaskContext {
                     cwd: Some("/dir".into()),
-                    env: HashMap::from_iter([
+                    task_variables: TaskVariables::from_iter([
                         ("ZED_FILE".into(), "/dir/rust/b.rs".into()),
                         ("ZED_WORKTREE_ROOT".into(), "/dir".into()),
                         ("ZED_ROW".into(), "1".into()),
@@ -379,7 +376,7 @@ mod tests {
                 task_context(this, task_cwd(this, cx).unwrap(), cx),
                 TaskContext {
                     cwd: Some("/dir".into()),
-                    env: HashMap::from_iter([
+                    task_variables: TaskVariables::from_iter([
                         ("ZED_FILE".into(), "/dir/rust/b.rs".into()),
                         ("ZED_WORKTREE_ROOT".into(), "/dir".into()),
                         ("ZED_SYMBOL".into(), "this_is_a_rust_file".into()),
@@ -396,7 +393,7 @@ mod tests {
                 task_context(this, task_cwd(this, cx).unwrap(), cx),
                 TaskContext {
                     cwd: Some("/dir".into()),
-                    env: HashMap::from_iter([
+                    task_variables: TaskVariables::from_iter([
                         ("ZED_FILE".into(), "/dir/a.ts".into()),
                         ("ZED_WORKTREE_ROOT".into(), "/dir".into()),
                         ("ZED_SYMBOL".into(), "this_is_a_test".into()),