Also show warnings when PRs are updated

src/handlers/assign.rs

@@ -22,7 +22,8 @@
 
 use crate::{
     config::{AssignConfig, WarnNonDefaultBranchException},
-    github::{self, Event, FileDiff, Issue, IssuesAction, Selection},
+    db::issue_data::IssueData,
+    github::{self, Event, FileDiff, Issue, IssuesAction, ReportedContentClassifiers, Selection},
     handlers::{pr_tracking::has_user_capacity, Context, GithubClient, IssuesEvent},
     interactions::EditIssueBody,
 };
@@ -116,6 +117,18 @@ const REVIEWER_ALREADY_ASSIGNED: &str =
 
 Please choose another assignee.";
 
+/// Key for teh state in the database
+const PULL_REQUEST_WARNINGS_KEY: &str = "pr-warnings";
+
+/// State stored in the database for a PR.
+#[derive(Debug, Default, serde::Deserialize, serde::Serialize)]
+struct PullRequestWarningsState {
+    /// 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>,
+}
+
 #[derive(Debug, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
 struct AssignData {
     user: Option<String>,
@@ -135,7 +148,10 @@ pub(super) async fn parse_input(
         None => return Ok(None),
     };
     if config.owners.is_empty()
-        || !matches!(event.action, IssuesAction::Opened)
+        || !matches!(
+            event.action,
+            IssuesAction::Opened | IssuesAction::Synchronize
+        )
         || !event.issue.is_pr()
     {
         return Ok(None);
@@ -159,7 +175,7 @@ pub(super) async fn handle_input(
     };
 
     // Don't auto-assign or welcome if the user manually set the assignee when opening.
-    if event.issue.assignees.is_empty() {
+    if matches!(event.action, IssuesAction::Opened) && event.issue.assignees.is_empty() {
         let (assignee, from_comment) = determine_assignee(ctx, event, config, &diff).await?;
         if assignee.as_deref() == Some("ghost") {
             // "ghost" is GitHub's placeholder account for deleted accounts.
@@ -214,20 +230,66 @@ pub(super) async fn handle_input(
         }
     }
 
-    // Compute some warning messages to post to new PRs.
+    // Get the state of the warnings for this issue in the database
+    let mut db = ctx.db.get().await;
+    let mut state: IssueData<'_, PullRequestWarningsState> =
+        IssueData::load(&mut db, &event.issue, PULL_REQUEST_WARNINGS_KEY).await?;
+
+    // Compute some warning messages to post to new (and old) PRs.
     let mut warnings = Vec::new();
     if let Some(exceptions) = config.warn_non_default_branch.enabled_and_exceptions() {
         warnings.extend(non_default_branch(exceptions, event));
     }
     warnings.extend(modifies_submodule(diff));
-    if !warnings.is_empty() {
+
+    // Add, hide or hide&add a comment with the warnings.
+    //
+    // 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.
+        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 hide a previous 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(())
 }