Also show warnings when PRs are updated

src/handlers/check_commits.rs

@@ -3,18 +3,35 @@ use anyhow::bail;
 use super::Context;
 use crate::{
     config::Config,
-    github::{Event, IssuesAction},
+    db::issue_data::IssueData,
+    github::{Event, IssuesAction, IssuesEvent, ReportedContentClassifiers},
 };
 
 mod modified_submodule;
 mod non_default_branch;
 
+/// Key for the state in the database
+const CHECK_COMMITS_WARNINGS_KEY: &str = "check-commits-warnings";
+
+/// State stored in the database
+#[derive(Debug, Default, serde::Deserialize, serde::Serialize)]
+struct CheckCommitsWarningsState {
+    /// List of the last warnings in the most recent comment.
+    last_warnings: Vec<String>,
+    /// ID of the most recent warning comment.
+    last_warned_comment: Option<String>,
+}
+
 pub(super) async fn handle(ctx: &Context, event: &Event, config: &Config) -> anyhow::Result<()> {
     let Event::Issue(event) = event else {
         return Ok(());
     };
 
-    if !matches!(event.action, IssuesAction::Opened) || !event.issue.is_pr() {
+    if !matches!(
+        event.action,
+        IssuesAction::Opened | IssuesAction::Synchronize
+    ) || !event.issue.is_pr()
+    {
         return Ok(());
     }
 
@@ -27,6 +44,7 @@ pub(super) async fn handle(ctx: &Context, event: &Event, config: &Config) -> any
 
     let mut warnings = Vec::new();
 
+    // Compute the warnings
     if let Some(assign_config) = &config.assign {
         // For legacy reasons the non-default-branch and modifies-submodule warnings
         // are behind the `[assign]` config.
@@ -40,14 +58,65 @@ pub(super) async fn handle(ctx: &Context, event: &Event, config: &Config) -> any
         warnings.extend(modified_submodule::modifies_submodule(diff));
     }
 
-    if !warnings.is_empty() {
+    handle_warnings(ctx, event, warnings).await
+}
+
+// Add, hide or hide&add a comment with the warnings.
+async fn handle_warnings(
+    ctx: &Context,
+    event: &IssuesEvent,
+    warnings: Vec<String>,
+) -> anyhow::Result<()> {
+    // Get the state of the warnings for this PR in the database.
+    let mut db = ctx.db.get().await;
+    let mut state: IssueData<'_, CheckCommitsWarningsState> =
+        IssueData::load(&mut db, &event.issue, CHECK_COMMITS_WARNINGS_KEY).await?;
+
+    // We only post a new comment when we haven't posted one with the same warnings before.
+    if !warnings.is_empty() && state.data.last_warnings != warnings {
+        // New set of warnings, let's post them.
+
+        // Hide a previous warnings comment if there was one before printing the new ones.
+        if let Some(last_warned_comment_id) = state.data.last_warned_comment {
+            event
+                .issue
+                .hide_comment(
+                    &ctx.github,
+                    &last_warned_comment_id,
+                    ReportedContentClassifiers::Resolved,
+                )
+                .await?;
+        }
+
+        // Format the warnings for user consumption on Github
         let warnings: Vec<_> = warnings
             .iter()
             .map(|warning| format!("* {warning}"))
             .collect();
         let warning = format!(":warning: **Warning** :warning:\n\n{}", warnings.join("\n"));
-        event.issue.post_comment(&ctx.github, &warning).await?;
-    };
+        let comment = event.issue.post_comment(&ctx.github, &warning).await?;
+
+        // Save new state in the database
+        state.data.last_warnings = warnings;
+        state.data.last_warned_comment = Some(comment.node_id);
+        state.save().await?;
+    } else if warnings.is_empty() {
+        // No warnings to be shown, let's resolve a previous warnings comment, if there was one.
+        if let Some(last_warned_comment_id) = state.data.last_warned_comment {
+            event
+                .issue
+                .hide_comment(
+                    &ctx.github,
+                    &last_warned_comment_id,
+                    ReportedContentClassifiers::Resolved,
+                )
+                .await?;
+
+            state.data.last_warnings = Vec::new();
+            state.data.last_warned_comment = None;
+            state.save().await?;
+        }
+    }
 
     Ok(())
 }