Begin job tagging implementation

crates/nu-command/src/experimental/job_list.rs

@@ -37,7 +37,7 @@ impl Command for JobList {
         let values = jobs
             .iter()
             .map(|(id, job)| {
-                let record = record! {
+                let mut record = record! {
                     "id" => Value::int(id.get() as i64, head),
                     "type" => match job {
                         Job::Thread(_) => Value::string("thread", head),
@@ -52,12 +52,16 @@ impl Command for JobList {
                             head,
                         ),
 
-                        Job::Frozen(FrozenJob { unfreeze }) => {
+                        Job::Frozen(FrozenJob { unfreeze, .. }) => {
                             Value::list(vec![ Value::int(unfreeze.pid() as i64, head) ], head)
                         }
-                    }
+                    },
                 };
 
+                if let Some(tag) = job.tag() {
+                    record.push("tag", Value::string(tag, head));
+                }
+
                 Value::record(record, head)
             })
             .collect::<Vec<Value>>();

crates/nu-command/src/experimental/job_spawn.rs

@@ -28,6 +28,12 @@ impl Command for JobSpawn {
         Signature::build("job spawn")
             .category(Category::Experimental)
             .input_output_types(vec![(Type::Nothing, Type::Int)])
+            .named(
+                "tag",
+                SyntaxShape::String,
+                "An optional description tag for this job",
+                Some('t'),
+            )
             .required(
                 "closure",
                 SyntaxShape::Closure(Some(vec![SyntaxShape::Any])),
@@ -50,6 +56,8 @@ impl Command for JobSpawn {
 
         let closure: Closure = call.req(engine_state, stack, 0)?;
 
+        let tag: Option<String> = call.get_flag(engine_state, stack, "tag")?;
+
         let mut job_state = engine_state.clone();
         job_state.is_interactive = false;
 
@@ -68,7 +76,7 @@ impl Command for JobSpawn {
         let mut jobs = jobs.lock().expect("jobs lock is poisoned!");
 
         let id = {
-            let thread_job = ThreadJob::new(job_signals);
+            let thread_job = ThreadJob::new(job_signals, tag);
             job_state.current_thread_job = Some(thread_job.clone());
             jobs.add_job(Job::Thread(thread_job))
         };

crates/nu-command/src/experimental/job_tag.rs

@@ -0,0 +1,64 @@
+use nu_engine::command_prelude::*;
+use nu_protocol::JobId;
+
+#[derive(Clone)]
+pub struct JobTag;
+
+impl Command for JobTag {
+    fn name(&self) -> &str {
+        "job tag"
+    }
+
+    fn description(&self) -> &str {
+        "Add a tag to a background job."
+    }
+
+    fn signature(&self) -> nu_protocol::Signature {
+        Signature::build("job tag")
+            .category(Category::Experimental)
+            .required("id", SyntaxShape::Int, "The id of the job to tag.")
+            .input_output_types(vec![(Type::Nothing, Type::Nothing)])
+            .allow_variants_without_examples(true)
+    }
+
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["describe", "desc"]
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        _input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        let head = call.head;
+
+        let id_arg: Spanned<i64> = call.req(engine_state, stack, 0)?;
+
+        if id_arg.item < 0 {
+            return Err(ShellError::NeedsPositiveValue { span: id_arg.span });
+        }
+
+        let id: JobId = JobId::new(id_arg.item as usize);
+
+        let mut jobs = engine_state.jobs.lock().expect("jobs lock is poisoned!");
+
+        if jobs.lookup(id).is_none() {
+            return Err(ShellError::JobNotFound {
+                id: id.get(),
+                span: head,
+            });
+        }
+
+        Ok(Value::nothing(head).into_pipeline_data())
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            example: "let id = job spawn { sleep 10sec }; job tag $id",
+            description: "tag a newly spawned job",
+            result: None,
+        }]
+    }
+}

crates/nu-command/src/experimental/job_unfreeze.rs

@@ -112,7 +112,10 @@ fn unfreeze_job(
             span,
         }),
 
-        Job::Frozen(FrozenJob { unfreeze: handle }) => {
+        Job::Frozen(FrozenJob {
+            unfreeze: handle,
+            tag,
+        }) => {
             let pid = handle.pid();
 
             if let Some(thread_job) = &state.current_thread_job {
@@ -141,7 +144,13 @@ fn unfreeze_job(
                 Ok(ForegroundWaitStatus::Frozen(handle)) => {
                     let mut jobs = state.jobs.lock().expect("jobs lock is poisoned!");
 
-                    jobs.add_job_with_id(old_id, Job::Frozen(FrozenJob { unfreeze: handle }))
+                    jobs.add_job_with_id(
+                        old_id,
+                        Job::Frozen(FrozenJob {
+                            unfreeze: handle,
+                            tag,
+                        }),
+                    )
                     .expect("job was supposed to be removed");
 
                     if state.is_interactive {

crates/nu-command/src/experimental/mod.rs

@@ -3,6 +3,7 @@ mod job;
 mod job_kill;
 mod job_list;
 mod job_spawn;
+mod job_tag;
 
 #[cfg(all(unix, feature = "os"))]
 mod job_unfreeze;

crates/nu-command/src/system/run_external.rs

@@ -332,7 +332,12 @@ impl Command for External {
                 if let ForegroundWaitStatus::Frozen(unfreeze) = status {
                     let mut jobs = jobs.lock().expect("jobs lock is poisoned!");
 
-                    let job_id = jobs.add_job(Job::Frozen(FrozenJob { unfreeze }));
+                    // TODO: use name of process as a tag
+                    let job_id = jobs.add_job(Job::Frozen(FrozenJob {
+                        unfreeze,
+                        tag: None,
+                    }));
+
                     if is_interactive {
                         println!("\nJob {} is frozen", job_id.get());
                     }

crates/nu-protocol/src/engine/jobs.rs

@@ -38,6 +38,10 @@ impl Jobs {
         self.jobs.get(&id)
     }
 
+    pub fn lookup_mut(&mut self, id: JobId) -> Option<&mut Job> {
+        self.jobs.get_mut(&id)
+    }
+
     pub fn remove_job(&mut self, id: JobId) -> Option<Job> {
         if self.last_frozen_job_id.is_some_and(|last| id == last) {
             self.last_frozen_job_id = None;
@@ -134,13 +138,15 @@ pub enum Job {
 pub struct ThreadJob {
     signals: Signals,
     pids: Arc<Mutex<HashSet<u32>>>,
+    tag: Option<String>,
 }
 
 impl ThreadJob {
-    pub fn new(signals: Signals) -> Self {
+    pub fn new(signals: Signals, tag: Option<String>) -> Self {
         ThreadJob {
             signals,
             pids: Arc::new(Mutex::new(HashSet::default())),
+            tag,
         }
     }
 
@@ -197,10 +203,18 @@ impl Job {
             Job::Frozen(frozen_job) => frozen_job.kill(),
         }
     }
+
+    pub fn tag(&self) -> Option<&String> {
+        match self {
+            Job::Thread(thread_job) => thread_job.tag.as_ref(),
+            Job::Frozen(frozen_job) => frozen_job.tag.as_ref(),
+        }
+    }
 }
 
 pub struct FrozenJob {
     pub unfreeze: UnfreezeHandle,
+    pub tag: Option<String>,
 }
 
 impl FrozenJob {