Improve rendered link handler with proper edit and sha-based link

src/handlers/rendered_link.rs

@@ -1,15 +1,25 @@
 use crate::{
     github::{Event, IssuesAction, IssuesEvent},
     handlers::Context,
+    interactions::EditIssueBody,
 };
 
+#[derive(Debug, PartialEq, Eq, serde::Serialize, serde::Deserialize, Default)]
+struct RenderedLinkData {
+    rendered_link: String,
+}
+
 pub async fn handle(ctx: &Context, event: &Event) -> anyhow::Result<()> {
     let e = if let Event::Issue(e) = event {
         e
     } else {
         return Ok(());
     };
 
+    if !e.issue.is_pr() {
+        return Ok(());
+    }
+
     let repo = e.issue.repository();
     let prefix = match (&*repo.organization, &*repo.repository) {
         ("rust-lang", "rfcs") => "text/",
@@ -25,32 +35,47 @@ pub async fn handle(ctx: &Context, event: &Event) -> anyhow::Result<()> {
 }
 
 async fn add_rendered_link(ctx: &Context, e: &IssuesEvent, prefix: &str) -> anyhow::Result<()> {
-    if e.action == IssuesAction::Opened {
+    if e.action == IssuesAction::Opened
+        || e.action == IssuesAction::Closed
+        || e.action == IssuesAction::Reopened
+    {
+        let edit = EditIssueBody::new(&e.issue, "RENDERED_LINK");
+        let current_data: Option<RenderedLinkData> = edit.current_data();
+
         let files = e.issue.files(&ctx.github).await?;
 
         if let Some(file) = files.iter().find(|f| f.filename.starts_with(prefix)) {
-            if !e.issue.body.contains("[Rendered]") {
-                // This URL should be stable while the PR is open, even if the
-                // user pushes new commits.
-                //
-                // It will go away if the user deletes their branch, or if
-                // they reset it (such as if they created a PR from master).
-                // That should usually only happen after the PR is closed.
-                // During the closing process, the closer should update the
-                // Rendered link to the new location (which we should
-                // automate!).
-                let head = e.issue.head.as_ref().unwrap();
-                let url = format!(
-                    "https://github.com/{}/blob/{}/{}",
-                    head.repo.full_name, head.git_ref, file.filename
-                );
-                e.issue
-                    .edit_body(
-                        &ctx.github,
-                        &format!("{}\n\n[Rendered]({})", e.issue.body, url),
-                    )
-                    .await?;
-            }
+            let mut current_data = current_data.unwrap_or_default();
+            let head = e.issue.head.as_ref().unwrap();
+
+            // This URL should be stable while the PR is open, even if the
+            // user pushes new commits.
+            //
+            // It will go away if the user deletes their branch, or if
+            // they reset it (such as if they created a PR from master).
+            // That should usually only happen after the PR is closed
+            // a which point we switch to a SHA-based url.
+            current_data.rendered_link = format!(
+                "https://github.com/{}/blob/{}/{}",
+                head.repo.full_name,
+                if e.action == IssuesAction::Closed {
+                    &head.sha
+                } else {
+                    &head.git_ref
+                },
+                file.filename
+            );
+
+            edit.apply(
+                &ctx.github,
+                format!("[Rendered]({})", &current_data.rendered_link),
+                current_data,
+            )
+            .await?;
+        } else if let Some(mut current_data) = current_data {
+            // No render link to show, but one previously, so remove it
+            current_data.rendered_link = String::new();
+            edit.apply(&ctx.github, String::new(), current_data).await?;
         }
     }