Render PR description as template (#2563)

<!--
Open the PR up as a draft until you feel it is ready for a proper
review.

Do not make PR:s from your own `main` branch, as that makes it difficult
for reviewers to add their own fixes.

Add any improvements to the branch as new commits to make it easier for
reviewers to follow the progress. All commits will be squashed to a
single commit once the PR is merged into `main`.

Make sure you mention any issues that this PR closes in the description,
as well as any other related issues.

To get an auto-generated PR description you can put "copilot:summary" or
"copilot:walkthrough" anywhere.
-->

### What

### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested [demo.rerun.io](https://demo.rerun.io/pr/2563) (if
applicable)

- [PR Build Summary](https://build.rerun.io/pr/2563)
- [Docs
preview](https://rerun.io/preview/pr%3Ajan%2Fsimplify-previews/docs)
- [Examples
preview](https://rerun.io/preview/pr%3Ajan%2Fsimplify-previews/examples)

.github/pull_request_template.md

@@ -15,9 +15,8 @@ To get an auto-generated PR description you can put "copilot:summary" or "copilo
 ### Checklist
 * [ ] I have read and agree to [Contributor Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and the [Code of Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
 * [ ] I've included a screenshot or gif (if applicable)
-* [ ] I have tested https://demo.rerun.io/pr/{{ pr-number }} (if applicable)
+* [ ] I have tested [demo.rerun.io](https://demo.rerun.io/pr/{{ pr.number }}) (if applicable)
 
-<!-- This line will get updated when the PR build summary job finishes. -->
-PR Build Summary: {{ pr-build-summary }}
-
-<!-- This comment will be replaced by a link to the documentation preview -->
+- [PR Build Summary](https://build.rerun.io/pr/{{ pr.number }})
+- [Docs preview](https://rerun.io/preview/{{ "pr:%s"|format(pr.branch)|encode_uri_component }}/docs)
+- [Examples preview](https://rerun.io/preview/{{ "pr:%s"|format(pr.branch)|encode_uri_component }}/examples)

.github/workflows/reusable_update_pr_body.yml

@@ -35,7 +35,7 @@ jobs:
           python-version: 3.x
 
       - name: Install deps
-        run: pip install PyGithub # NOLINT
+        run: pip install Jinja2 PyGithub # NOLINT
 
       - name: Update PR description
         run: |

scripts/ci/generate_pr_summary.py

@@ -87,11 +87,6 @@ def generate_pr_summary(github_token: str, github_repository: str, pr_number: in
         print(f"Uploading results to {upload_blob.name}")
         upload_blob.upload_from_file(buffer, content_type="text/html")
 
-        # If there's a {{ pr-build-summary }} string in the PR description, replace it with a link to the summary page.
-        pr_description = pull.body
-        new_description = pr_description.replace("{{ pr-build-summary }}", f"https://build.rerun.io/pr/{pr_number}")
-        pull.edit(body=new_description)
-
 
 def main() -> None:
     parser = argparse.ArgumentParser(description="Generate a PR summary page")

scripts/ci/update_pr_body.py

@@ -1,30 +1,30 @@
 #!/usr/bin/env python3
 
 """
-Script to generate a link to documentation preview in PRs.
+Script to update the PR description template.
 
 This is expected to be run by the `reusable_update_pr_body.yml` GitHub workflow.
 
 Requires the following packages:
-  pip install PyGithub # NOLINT
+  pip install Jinja2 PyGithub # NOLINT
 """
 from __future__ import annotations
 
 import argparse
+import logging
+import urllib.parse
 
 from github import Github  # NOLINT
+from jinja2 import DebugUndefined, select_autoescape
+from jinja2.sandbox import SandboxedEnvironment
 
-EMPTY_LINK = "<!-- This comment will be replaced by a link to the documentation preview -->"
-LINK_START = "<!-- pr-link-docs:start -->"
-LINK_END = "<!-- pr-link-docs:end -->"
 
-LINK_TEMPLATE = """<!-- pr-link-docs:start -->
-Docs preview: {{ docs-link }}
-Examples preview: {{ examples-link }}
-<!-- pr-link-docs:end -->"""
+def encode_uri_component(value: str) -> str:
+    return urllib.parse.quote(value, safe="")
 
 
 def main() -> None:
+    logging.getLogger().setLevel(-1)
     parser = argparse.ArgumentParser(description="Generate a PR summary page")
     parser.add_argument("--github-token", required=True, help="GitHub token")
     parser.add_argument("--github-repository", required=True, help="GitHub repository")
@@ -38,26 +38,19 @@ def main() -> None:
     latest_commit = pr.get_commits().reversed[0]
 
     print(f"Latest commit: {latest_commit.sha}")
-    short_sha = latest_commit.sha[:7]
-
-    body = pr.body
-
-    # update preview links
-    link = LINK_TEMPLATE.replace("{{ docs-link }}", f"https://rerun.io/preview/{short_sha}/docs")
-    link = link.replace("{{ examples-link }}", f"https://rerun.io/preview/{short_sha}/examples")
-    if EMPTY_LINK in body:
-        print("Empty link found, updating it")
-        body = body.replace(EMPTY_LINK, link)
-    else:
-        start = body.find(LINK_START)
-        end = body.find(LINK_END)
-        if start != -1 and end != -1:
-            print("Existing link found, updating it")
-            body = body[:start] + link + body[end + len(LINK_END) :]
-
-    # update the pr number
-    if "{{ pr-number }}" in body:
-        body = body.replace("{{ pr-number }}", str(args.pr_number))
+
+    env = SandboxedEnvironment(
+        autoescape=select_autoescape(),
+        undefined=DebugUndefined,
+    )
+    env.filters["encode_uri_component"] = encode_uri_component
+
+    body = env.from_string(pr.body).render(
+        pr={
+            "number": args.pr_number,
+            "branch": pr.head.ref,
+        },
+    )
 
     if body != pr.body:
         pr.edit(body=body)