fix: Fix failure to copy description (#29)

Instead of copying the PR title and body from the HTML elements, which may not exist yet, use the GitHub API to query the necessary metadata.
If the API query fails, attempt to make the PR body HTML elements load by opening the PR description for edit and immediately canceling the edit.  

Closes #11

Co-authored-by: Zach Whaley <[email protected]>

Author: joeyparrish

content.js

@@ -6,28 +6,34 @@ function debug(message) {
   console.debug(`squashed-merge-message: ${message}`);
 }
 
-function copyPrDescription() {
+async function copyPrDescription() {
   debug('copy PR description');
-  const prTitleEl = document.getElementById('issue_title');
-  if (!prTitleEl) {
-    warn('failed to find PR title element');
-    return;
-  };
 
-  const prNumberMatch = window.location.pathname.match('/pull/(?<pr_number>[0-9]+)$');
-  if (!prNumberMatch) {
-    warn('failed to find match for PR number in URL');
+  const match = window.location.pathname.match('^/(?<repo>[^/]+/[^/]+)/pull/(?<pr_number>[0-9]+)$');
+  if (!match) {
+    warn('failed to find match for repo and PR number in URL');
     return;
   };
+  const repo = match.groups['repo'];
+  const prNumber = match.groups['pr_number'];
 
-  let prBodyEl = document.querySelector('.comment-form-textarea[name="issue[body]"]');
-  if (!prBodyEl) {
-    prBodyEl = document.querySelector('.comment-form-textarea[name="pull_request[body]"]');
-    if (!prBodyEl) {
-      warn('failed to find PR body element');
-      return;
-    };
-  };
+  let prMetadata = null;
+
+  // For public repos, prefer the API.
+  if (window.location.host === 'github.com') {
+    prMetadata = await getPrMetadataFromApi(repo, prNumber);
+  }
+
+  // If that fails, try manipulating the document.
+  if (!prMetadata) {
+    prMetadata = await getPrMetadataFromDocument();
+  }
+
+  // If that fails... we fail!
+  if (!prMetadata) {
+    warn('failed to pull PR metadata from document or API');
+    return;
+  }
 
   // When using auto-merge, GitHub has two text fields with the same ID.
   const titleFields = document.querySelectorAll('[id=merge_title_field]');
@@ -43,10 +49,10 @@ function copyPrDescription() {
     return;
   };
 
-  const commitTitle = `${prTitleEl.value} (#${prNumberMatch.groups['pr_number']})`;
+  const commitTitle = `${prMetadata.title} (#${prNumber})`;
 
   // Remove leading HTML comments
-  let commitBody = prBodyEl.textContent.replace(/^<!--.*?-->\n*/gs, '');
+  let commitBody = prMetadata.body.replace(/^<!--.*?-->\n*/gs, '').trim();
 
   // Preserve and de-duplicate co-authors
   const coauthors = new Set(messageFields[0].value.match(/Co-authored-by: .*/g));
@@ -58,6 +64,51 @@ function copyPrDescription() {
   messageFields.forEach(f => f.value = commitBody);
 }
 
+async function getPrMetadataFromDocument() {
+  await makePrDescriptionAppear();
+
+  const prTitleEl = document.getElementById('issue_title');
+  if (!prTitleEl) {
+    warn('failed to find PR title element');
+    return null;
+  }
+
+  let prBodyEl = document.querySelector('.comment-form-textarea[name="issue[body]"]');
+  if (!prBodyEl) {
+    prBodyEl = document.querySelector('.comment-form-textarea[name="pull_request[body]"]');
+    if (!prBodyEl) {
+      warn('failed to find PR body element');
+      return null;
+    }
+  }
+
+  return {
+    title: prTitleEl.value,
+    body: prBodyEl.textContent,
+  };
+}
+
+async function getPrMetadataFromApi(repo, prNumber) {
+  const response = await fetch(`https://api.github.com/repos/${repo}/pulls/${prNumber}`);
+  const prMetadata = await response.json();
+  return {
+    // These could be null in some cases, so replace nulls with empty strings.
+    title: prMetadata.title || '',
+    body: prMetadata.body || '',
+  };
+}
+
+async function makePrDescriptionAppear() {
+  const detailsButton = document.querySelector('.timeline-comment-actions details:last-child summary[role="button"]');
+  detailsButton.click();
+  const editButton = await waitForElement('details-menu > button.dropdown-item.btn-link.js-comment-edit-button');
+  editButton.click();
+  const cancelButton = await waitForElement('button.js-comment-cancel-button.btn-danger.btn');
+  cancelButton.click();
+  const commitText = document.getElementById('merge_message_field');
+  commitText.focus();
+}
+
 function waitForElement(selector) {
   debug(`wait for element ${selector}`);
   return new Promise(resolve => {