From e8d017a958ed09877430ee1a834ec31e5b23e10d Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Sun, 8 Dec 2024 15:25:10 -0500
Subject: [PATCH] Add github-action PR open/closer

---
 src/config.rs                     |  8 +++++++
 src/github.rs                     | 25 +++++++++++++++++++
 src/handlers.rs                   | 11 +++++++++
 src/handlers/bot_pull_requests.rs | 40 +++++++++++++++++++++++++++++++
 4 files changed, 84 insertions(+)
 create mode 100644 src/handlers/bot_pull_requests.rs

diff --git a/src/config.rs b/src/config.rs
index 8b6fa5f6..6a7480ba 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -46,6 +46,7 @@ pub(crate) struct Config {
     pub(crate) pr_tracking: Option<ReviewPrefsConfig>,
     pub(crate) transfer: Option<TransferConfig>,
     pub(crate) merge_conflicts: Option<MergeConflictConfig>,
+    pub(crate) bot_pull_requests: Option<BotPullRequests>,
 }
 
 #[derive(PartialEq, Eq, Debug, serde::Deserialize)]
@@ -402,6 +403,11 @@ pub(crate) struct MergeConflictConfig {
     pub unless: HashSet<String>,
 }
 
+#[derive(PartialEq, Eq, Debug, serde::Deserialize)]
+#[serde(rename_all = "kebab-case")]
+#[serde(deny_unknown_fields)]
+pub(crate) struct BotPullRequests {}
+
 fn get_cached_config(repo: &str) -> Option<Result<Arc<Config>, ConfigurationError>> {
     let cache = CONFIG_CACHE.read().unwrap();
     cache.get(repo).and_then(|(config, fetch_time)| {
@@ -580,6 +586,7 @@ mod tests {
                 pr_tracking: None,
                 transfer: None,
                 merge_conflicts: None,
+                bot_pull_requests: None,
             }
         );
     }
@@ -641,6 +648,7 @@ mod tests {
                 pr_tracking: None,
                 transfer: None,
                 merge_conflicts: None,
+                bot_pull_requests: None,
             }
         );
     }
diff --git a/src/github.rs b/src/github.rs
index e05e0f31..cbf7ed78 100644
--- a/src/github.rs
+++ b/src/github.rs
@@ -189,6 +189,31 @@ impl GithubClient {
         .await
         .context("failed to create issue")
     }
+
+    pub(crate) async fn set_pr_state(
+        &self,
+        repo: &IssueRepository,
+        number: u64,
+        state: PrState,
+    ) -> anyhow::Result<()> {
+        #[derive(serde::Serialize)]
+        struct Update {
+            state: PrState,
+        }
+        let url = format!("{}/pulls/{number}", repo.url(&self));
+        self.send_req(self.patch(&url).json(&Update { state }))
+            .await
+            .context("failed to update pr state")?;
+        Ok(())
+    }
+}
+
+#[derive(Debug, serde::Serialize)]
+pub(crate) enum PrState {
+    #[serde(rename = "open")]
+    Open,
+    #[serde(rename = "closed")]
+    Closed,
 }
 
 #[derive(Debug, serde::Deserialize)]
diff --git a/src/handlers.rs b/src/handlers.rs
index 759c5441..9218a210 100644
--- a/src/handlers.rs
+++ b/src/handlers.rs
@@ -25,6 +25,7 @@ impl fmt::Display for HandlerError {
 
 mod assign;
 mod autolabel;
+mod bot_pull_requests;
 mod close;
 pub mod docs_update;
 mod github_releases;
@@ -117,6 +118,16 @@ pub async fn handle(ctx: &Context, event: &Event) -> Vec<HandlerError> {
         );
     }
 
+    if config.as_ref().is_ok_and(|c| c.bot_pull_requests.is_some()) {
+        if let Err(e) = bot_pull_requests::handle(ctx, event).await {
+            log::error!(
+                "failed to process event {:?} with bot_pull_requests handler: {:?}",
+                event,
+                e
+            )
+        }
+    }
+
     if let Some(config) = config
         .as_ref()
         .ok()
diff --git a/src/handlers/bot_pull_requests.rs b/src/handlers/bot_pull_requests.rs
new file mode 100644
index 00000000..02e4ec2e
--- /dev/null
+++ b/src/handlers/bot_pull_requests.rs
@@ -0,0 +1,40 @@
+use crate::github::{IssuesAction, PrState};
+use crate::{github::Event, handlers::Context};
+
+pub(crate) async fn handle(ctx: &Context, event: &Event) -> anyhow::Result<()> {
+    let Event::Issue(event) = event else {
+        return Ok(());
+    };
+    // Note that this filters out reopened too, which is what we'd expect when we set the state
+    // back to opened after closing.
+    if event.action != IssuesAction::Opened {
+        return Ok(());
+    }
+    if !event.issue.is_pr() {
+        return Ok(());
+    }
+
+    // avoid acting on our own open events, otherwise we'll infinitely loop
+    if event.sender.login == ctx.username {
+        return Ok(());
+    }
+
+    // If it's not the github-actions bot, we don't expect this handler to be needed. Skip the
+    // event.
+    if event.sender.login != "app/github-actions" {
+        return Ok(());
+    }
+
+    ctx.github
+        .set_pr_state(
+            event.issue.repository(),
+            event.issue.number,
+            PrState::Closed,
+        )
+        .await?;
+    ctx.github
+        .set_pr_state(event.issue.repository(), event.issue.number, PrState::Open)
+        .await?;
+
+    Ok(())
+}