Accept/decline T-compiler backports from Zulip

src/github.rs

@@ -1319,9 +1319,6 @@ impl IssuesEvent {
     }
 }
 
-#[derive(Debug, serde::Deserialize)]
-struct PullRequestEventFields {}
-
 #[derive(Debug, serde::Deserialize)]
 pub struct WorkflowRunJob {
     pub name: String,

src/handlers/backport.rs

@@ -4,6 +4,7 @@ use std::sync::LazyLock;
 use crate::config::BackportConfig;
 use crate::github::{IssuesAction, IssuesEvent, Label};
 use crate::handlers::Context;
+use crate::utils::contains_any;
 use anyhow::Context as AnyhowContext;
 use futures::future::join_all;
 use regex::Regex;
@@ -204,10 +205,6 @@ pub(super) async fn handle_input(
     Ok(())
 }
 
-fn contains_any(haystack: &[&str], needles: &[&str]) -> bool {
-    needles.iter().any(|needle| haystack.contains(needle))
-}
-
 #[cfg(test)]
 mod tests {
     use crate::handlers::backport::CLOSES_ISSUE_REGEXP;

src/utils.rs

@@ -61,3 +61,7 @@ pub(crate) async fn is_repo_autorized(
 
     Ok(true)
 }
+
+pub fn contains_any(haystack: &[&str], needles: &[&str]) -> bool {
+    needles.iter().any(|needle| haystack.contains(needle))
+}

src/zulip.rs

@@ -13,7 +13,7 @@ use crate::handlers::docs_update::docs_update;
 use crate::handlers::pr_tracking::get_assigned_prs;
 use crate::handlers::project_goals::{self, ping_project_goals_owners};
 use crate::interactions::ErrorComment;
-use crate::utils::pluralize;
+use crate::utils::{contains_any, pluralize};
 use crate::zulip::api::{MessageApiResponse, Recipient};
 use crate::zulip::client::ZulipClient;
 use crate::zulip::commands::{
@@ -24,12 +24,34 @@ use axum::Json;
 use axum::extract::State;
 use axum::extract::rejection::JsonRejection;
 use axum::response::IntoResponse;
+use commands::BackportArgs;
+use octocrab::Octocrab;
 use rust_team_data::v1::{TeamKind, TeamMember};
 use std::cmp::Reverse;
 use std::fmt::Write as _;
 use std::sync::Arc;
 use subtle::ConstantTimeEq;
-use tracing as log;
+use tracing::log;
+
+fn get_text_backport_approved(channel: &str, verb: &str, zulip_link: &str) -> String {
+    format!("
+{channel} backport {verb} as per compiler team [on Zulip]({zulip_link}). A backport PR will be authored by the release team at the end of the current development cycle. Backport labels handled by them.
+
+@rustbot label +{channel}-accepted")
+}
+
+fn get_text_backport_declined(channel: &str, verb: &str, zulip_link: &str) -> String {
+    format!(
+        "
+{channel} backport {verb} as per compiler team [on Zulip]({zulip_link}).
+
+@rustbot label -{channel}-nominated"
+    )
+}
+
+const BACKPORT_CHANNELS: [&str; 2] = ["beta", "stable"];
+const BACKPORT_VERBS_APPROVE: [&str; 4] = ["accept", "accepted", "approve", "approved"];
+const BACKPORT_VERBS_DECLINE: [&str; 2] = ["decline", "declined"];
 
 #[derive(Debug, serde::Deserialize)]
 pub struct Request {
@@ -302,10 +324,71 @@ async fn handle_command<'a>(
                 .map_err(|e| format_err!("Failed to await at this time: {e:?}")),
             StreamCommand::PingGoals(args) => ping_goals_cmd(ctx, gh_id, message_data, &args).await,
             StreamCommand::DocsUpdate => trigger_docs_update(message_data, &ctx.zulip),
+            StreamCommand::Backport(args) => {
+                accept_decline_backport(message_data, &ctx.octocrab, &ctx.zulip, &args).await
+            }
         }
     }
 }
 
+// TODO: shorter variant of this command (f.e. `backport accept` or even `accept`) that infers everything from the Message payload
+async fn accept_decline_backport(
+    message_data: &Message,
+    octo_client: &Octocrab,
+    zulip_client: &ZulipClient,
+    args_data: &BackportArgs,
+) -> anyhow::Result<Option<String>> {
+    let message = message_data.clone();
+    let args = args_data.clone();
+    let stream_id = message.stream_id.unwrap();
+    let subject = message.subject.unwrap();
+    let verb = args.verb.to_lowercase();
+    let octo_client = octo_client.clone();
+
+    // Repository owner and name are hardcoded
+    // This command is only used in this repository
+    let repo_owner = "rust-lang";
+    let repo_name = "rust";
+
+    // validate command parameters
+    if !contains_any(&[args.channel.to_lowercase().as_str()], &BACKPORT_CHANNELS) {
+        return Err(anyhow::anyhow!(
+            "Parser error: unknown channel (allowed: {BACKPORT_CHANNELS:?})."
+        ));
+    }
+
+    // TODO: factor out the Zulip "URL encoder" to make it practical to use
+    let zulip_send_req = crate::zulip::MessageApiRequest {
+        recipient: Recipient::Stream {
+            id: stream_id,
+            topic: &subject,
+        },
+        content: "",
+    };
+    let zulip_link = zulip_send_req.url(zulip_client);
+
+    let message_body = if contains_any(&[verb.as_str()], &BACKPORT_VERBS_APPROVE) {
+        get_text_backport_approved(&args.channel, &verb, &zulip_link)
+    } else if contains_any(&[verb.as_str()], &BACKPORT_VERBS_DECLINE) {
+        get_text_backport_declined(&args.channel, &verb, &zulip_link)
+    } else {
+        return Err(anyhow::anyhow!(
+            "Parser error: unknown verb (allowed: {BACKPORT_VERBS_APPROVE:?} or {BACKPORT_VERBS_DECLINE:?})"
+        ));
+    };
+
+    let res = octo_client
+        .issues(repo_owner, repo_name)
+        .create_comment(args.pr_num, &message_body)
+        .await
+        .with_context(|| anyhow::anyhow!("unable to post comment on #{}", args.pr_num));
+    if res.is_err() {
+        tracing::error!("failed to post comment: {0:?}", res.err());
+    }
+
+    Ok(Some("".to_string()))
+}
+
 async fn ping_goals_cmd(
     ctx: Arc<Context>,
     gh_id: u64,

src/zulip/commands.rs

@@ -1,5 +1,6 @@
 use crate::db::notifications::Identifier;
 use crate::db::review_prefs::RotationMode;
+use crate::github::PullRequestNumber;
 use clap::{ColorChoice, Parser};
 use std::num::NonZeroU32;
 use std::str::FromStr;
@@ -161,8 +162,10 @@ pub enum StreamCommand {
     Read,
     /// Ping project goal owners.
     PingGoals(PingGoalsArgs),
-    /// Update docs
+    /// Update docs.
     DocsUpdate,
+    /// Accept or decline a backport.
+    Backport(BackportArgs),
 }
 
 #[derive(clap::Parser, Debug, PartialEq, Clone)]
@@ -173,6 +176,16 @@ pub struct PingGoalsArgs {
     pub next_update: String,
 }
 
+#[derive(clap::Parser, Debug, PartialEq, Clone)]
+pub struct BackportArgs {
+    /// Release channel this backport is pointing to. Allowed: "beta" or "stable".
+    pub channel: String,
+    /// Accept or decline this backport? Allowed: "accept", "accepted", "approve", "approved", "decline", "declined".
+    pub verb: String,
+    /// PR to be backported
+    pub pr_num: PullRequestNumber,
+}
+
 /// Helper function to parse CLI arguments without any colored help or error output.
 pub fn parse_cli<'a, T: Parser, I: Iterator<Item = &'a str>>(input: I) -> anyhow::Result<T> {
     fn allow_title_case(sub: clap::Command) -> clap::Command {
@@ -292,6 +305,26 @@ mod tests {
         assert_eq!(parse_stream(&["await"]), StreamCommand::EndTopic);
     }
 
+    #[test]
+    fn backports_command() {
+        assert_eq!(
+            parse_stream(&["backport", "beta", "accept", "123456"]),
+            StreamCommand::Backport(BackportArgs {
+                channel: "beta".to_string(),
+                verb: "accept".to_string(),
+                pr_num: 123456
+            })
+        );
+        assert_eq!(
+            parse_stream(&["backport", "stable", "decline", "123456"]),
+            StreamCommand::Backport(BackportArgs {
+                channel: "stable".to_string(),
+                verb: "decline".to_string(),
+                pr_num: 123456
+            })
+        );
+    }
+
     fn parse_chat(input: &[&str]) -> ChatCommand {
         parse_cli::<ChatCommand, _>(input.into_iter().copied()).unwrap()
     }