Add alias for compound labels

Configure relabel command aliases from the `triagebot.toml`.

Does not handle the case of multiple labels and command aliases intermixed, example:
@rustbot label cmd-alias label1 cmd-label1

In case a valid alias is parsed, the rest will be discarded, example:
@rustbot cmd-alias label1

is the same as:
@rustbot cmd-alias

skip-checks: true

Author: apiraino

parser/src/command/relabel.rs

@@ -19,7 +19,7 @@ pub enum LabelDelta {
 }
 
 #[derive(Debug, PartialEq, Eq, Clone)]
-pub struct Label(String);
+pub struct Label(pub String);
 
 #[derive(PartialEq, Eq, Debug)]
 pub enum ParseError {
@@ -103,6 +103,7 @@ fn delta_empty() {
 }
 
 impl RelabelCommand {
+    /// Parse and validate command tokens
     pub fn parse<'a>(input: &mut Tokenizer<'a>) -> Result<Option<Self>, Error<'a>> {
         let mut toks = input.clone();
 
@@ -261,3 +262,39 @@ fn parse_quote() {
         ]))
     );
 }
+
+#[test]
+fn parse_command_1() {
+    assert_eq!(
+        parse("labels to-stable"),
+        Ok(Some(vec![
+            LabelDelta::Add(Label("regression-from-stable-to-stable".into())),
+            LabelDelta::Remove(Label("regression-from-stable-to-beta".into())),
+            LabelDelta::Remove(Label("regression-from-stable-to-nightly".into()))
+        ]))
+    );
+}
+
+#[test]
+fn parse_command_2() {
+    assert_eq!(
+        parse("labels to-beta"),
+        Ok(Some(vec![
+            LabelDelta::Add(Label("regression-from-stable-to-beta".into())),
+            LabelDelta::Remove(Label("regression-from-stable-to-stable".into())),
+            LabelDelta::Remove(Label("regression-from-stable-to-nightly".into()))
+        ]))
+    );
+}
+
+#[test]
+fn parse_command_variants() {
+    assert_eq!(
+        parse("labels: to-beta"),
+        Ok(Some(vec![
+            LabelDelta::Add(Label("regression-from-stable-to-beta".into())),
+            LabelDelta::Remove(Label("regression-from-stable-to-stable".into())),
+            LabelDelta::Remove(Label("regression-from-stable-to-nightly".into()))
+        ]))
+    );
+}

src/config.rs

@@ -1,5 +1,6 @@
 use crate::changelogs::ChangelogFormat;
 use crate::github::{GithubClient, Repository};
+use parser::command::relabel::{Label, LabelDelta, RelabelCommand};
 use std::collections::{HashMap, HashSet};
 use std::fmt;
 use std::sync::{Arc, LazyLock, RwLock};
@@ -238,10 +239,36 @@ pub(crate) struct MentionsPathConfig {
 
 #[derive(PartialEq, Eq, Debug, serde::Deserialize)]
 #[serde(rename_all = "kebab-case")]
-#[serde(deny_unknown_fields)]
 pub(crate) struct RelabelConfig {
     #[serde(default)]
     pub(crate) allow_unauthenticated: Vec<String>,
+    // alias identifier -> labels
+    #[serde(flatten)]
+    pub(crate) configs: Option<HashMap<String, RelabelRuleConfig>>,
+}
+
+#[derive(Default, PartialEq, Eq, Debug, serde::Deserialize)]
+#[serde(rename_all = "kebab-case")]
+#[serde(deny_unknown_fields)]
+pub(crate) struct RelabelRuleConfig {
+    /// Labels to be added
+    pub(crate) add_labels: Vec<String>,
+    /// Labels to be removed
+    pub(crate) rem_labels: Vec<String>,
+}
+
+impl RelabelRuleConfig {
+    /// Translate a RelabelRuleConfig into a RelabelCommand for GitHub consumption
+    pub fn to_command(&self) -> RelabelCommand {
+        let mut deltas = Vec::new();
+        for l in self.add_labels.iter() {
+            deltas.push(LabelDelta::Add(Label(l.into())));
+        }
+        for l in self.rem_labels.iter() {
+            deltas.push(LabelDelta::Remove(Label(l.into())));
+        }
+        RelabelCommand(deltas)
+    }
 }
 
 #[derive(PartialEq, Eq, Debug, serde::Deserialize)]
@@ -756,6 +783,7 @@ mod tests {
             Config {
                 relabel: Some(RelabelConfig {
                     allow_unauthenticated: vec!["C-*".into()],
+                    configs: Some(HashMap::new())
                 }),
                 assign: Some(AssignConfig {
                     warn_non_default_branch: WarnNonDefaultBranchConfig::Simple(false),
@@ -926,4 +954,36 @@ mod tests {
             })
         );
     }
+
+    #[test]
+    fn relabel_new_config() {
+        let config = r#"
+            [relabel]
+            allow-unauthenticated = ["ABCD-*"]
+
+            [relabel.to-stable]
+            add-labels = ["regression-from-stable-to-stable"]
+            rem-labels = ["regression-from-stable-to-beta", "regression-from-stable-to-nightly"]
+        "#;
+        let config = toml::from_str::<Config>(&config).unwrap();
+
+        let mut relabel_configs = HashMap::new();
+        relabel_configs.insert(
+            "to-stable".into(),
+            RelabelRuleConfig {
+                add_labels: vec!["regression-from-stable-to-stable".to_string()],
+                rem_labels: vec![
+                    "regression-from-stable-to-beta".to_string(),
+                    "regression-from-stable-to-nightly".to_string(),
+                ],
+            },
+        );
+
+        let expected_cfg = RelabelConfig {
+            allow_unauthenticated: vec!["ABCD-*".to_string()],
+            configs: Some(relabel_configs),
+        };
+
+        assert_eq!(config.relabel, Some(expected_cfg));
+    }
 }

src/handlers/relabel.rs

@@ -24,9 +24,30 @@ pub(super) async fn handle_command(
     event: &Event,
     input: RelabelCommand,
 ) -> anyhow::Result<()> {
-    let mut results = vec![];
+    let mut to_rem = vec![];
     let mut to_add = vec![];
-    for delta in &input.0 {
+
+    // Parse alias configurations, look for a match in the input
+    // If it does, extract the appropriate config (RelabelRuleConfig) and build a new RelabelCommand.
+    // TODO: handle the case of multiple labels and cmd aliases mixed together
+    // TODO: (example: "@rustbot label cmd-alias label cmd-label-1 label1")
+    // TODO: one option is to interpret only the first token and discard the rest
+    let new_input = match &config.configs {
+        Some(configs) => {
+            // extract the "alias" from the RelabelCommand
+            let maybe_cmd_alias = input.0.get(0).unwrap();
+            let maybe_cmd_alias = maybe_cmd_alias.label();
+
+            // check if this alias matches any RelabelRuleConfig key in our config
+            // extract the labels and build a new command
+            let (_alias, cfg) = configs.get_key_value(maybe_cmd_alias.as_str()).unwrap();
+            cfg.to_command()
+        }
+        None => input,
+    };
+
+    // Parse input label command, checks permissions, built GitHub commands
+    for delta in &new_input.0 {
         let name = delta.label().as_str();
         let err = match check_filter(name, config, is_member(&event.user(), &ctx.team).await) {
             Ok(CheckFilterResult::Allow) => None,
@@ -53,14 +74,12 @@ pub(super) async fn handle_command(
                 });
             }
             LabelDelta::Remove(label) => {
-                results.push((
-                    label,
-                    event.issue().unwrap().remove_label(&ctx.github, &label),
-                ));
+                to_rem.push(label);
             }
         }
     }
 
+    // Add new labels (if needed)
     if let Err(e) = event
         .issue()
         .unwrap()
@@ -84,8 +103,14 @@ pub(super) async fn handle_command(
         return Err(e);
     }
 
-    for (label, res) in results {
-        if let Err(e) = res.await {
+    // Remove labels (if needed)
+    for label in to_rem {
+        if let Err(e) = event
+            .issue()
+            .unwrap()
+            .remove_label(&ctx.github, &label)
+            .await
+        {
             tracing::error!(
                 "failed to remove {:?} from issue {}: {:?}",
                 label,
@@ -124,6 +149,8 @@ enum CheckFilterResult {
     DenyUnknown,
 }
 
+/// Check if the team member is allowed to apply labels
+/// configured in `allow_unauthenticated`
 fn check_filter(
     label: &str,
     config: &RelabelConfig,
@@ -220,6 +247,7 @@ mod tests {
             ($($member:ident { $($label:expr => $res:ident,)* })*) => {
                 let config = RelabelConfig {
                     allow_unauthenticated: vec!["T-*".into(), "I-*".into(), "!I-*nominated".into()],
+                    configs: None
                 };
                 $($(assert_eq!(
                     check_filter($label, &config, TeamMembership::$member),