update macro to lookup point releases for artifacts (#4831)

* update macro to lookup point releases for artifacts

* remove trailing whitespace

* use vargs to be explicit

* name the github client more explicitly

* drop pre-v1 support

* better naming for GithubRleases

* remove the full knative-prefix

* allow the macro helper to accept knative-v1.3.0 and v1.30.0

* handle the repos with bad tags

* better log message

* support go tag format as a fallback

* refactor so we use the GitHub release tag

Some repos we link to don't have the knative- prefix in their release tag

hack/macros.py

@@ -1,6 +1,69 @@
 import os
+import semver
+import sys
+import traceback
+
+from github import Github
+
+# By default mkdocs swallows print() messages from macros
+def print_to_stdout(*vargs):
+    print(*vargs, file = sys.stdout)
+
+def drop_prefix(tag):
+    tag = tag.removeprefix("knative-")
+    tag = tag.removeprefix("v")
+    return tag
+
+def is_major_minor(tag, version):
+    tag = drop_prefix(tag)
+    return tag.startswith(f'{version.major}.{version.minor}')
+
+def safe_semver_parse(tag):
+    tag = drop_prefix(tag)
+    try:
+        return semver.VersionInfo.parse(tag)
+    except:
+        # If the tag isn't semver
+        return semver.VersionInfo.parse('0.0.0')
+
+class GithubReleases:
+    def __init__(self):
+        self.tags_for_repo = {}
+        self.client = Github(os.getenv("GITHUB_TOKEN"))
+
+    def __get_latest(self, version, org, repo):
+        key = f'{org}/{repo}'
+
+        if key not in self.tags_for_repo:
+            tags = []
+            for release in self.client.get_repo(key, lazy=True).get_releases():
+                tags.append(release.tag_name)
+
+            tags.sort(key=safe_semver_parse, reverse=True)
+            self.tags_for_repo[key] = tags
+
+        tags = self.tags_for_repo[key]
+        tags = list(filter(lambda tag: is_major_minor(tag, version), tags))
+
+        if len(tags) > 0:
+            return tags[0]
+        else:
+            return None
+
+    def get_latest_tag(self, version, org, repo):
+        tag = self.__get_latest(version, org, repo)
+
+        if tag is not None:
+            return tag
+
+        # Try the go.mod tag format 'v0.x.y' if v1.x.y doesn't work
+        # knative-v1.0.0 = v0.27.0
+        version = version.replace(major=version.major-1, minor=version.minor+27)
+        return self.__get_latest(version, org, repo)
+
 
 def define_env(env):
+    releases = GithubReleases()
 
     @env.macro
     def feature(alpha="", beta="", stable=""):
@@ -25,24 +88,30 @@ def define_env(env):
         empty this links to googlestorage, otherwise it links via
         the matching release in github.
         """
+
         version = os.environ.get("KNATIVE_VERSION")
+
         if version == None:
-            return 'https://storage.googleapis.com/knative-nightly/{repo}/latest/{file}'.format(
-                    repo=repo,
-                    file=file)
-        else:
-            if version.startswith("v1."):
-                return 'https://github.com/{org}/{repo}/releases/download/knative-{version}/{file}'.format(
-                    repo=repo,
-                    file=file,
-                    version=version,
-                    org=org)
+            return f'https://storage.googleapis.com/knative-nightly/{repo}/latest/{file}'
+
+        version = drop_prefix(version)
+
+        try:
+            v = semver.VersionInfo.parse(version)
+            latest_version_tag = releases.get_latest_tag(v, org, repo)
+
+            if latest_version_tag is None:
+                print_to_stdout(f'repo "{org}/{repo}" has no tags for version "{version}" using latest release for file "{file}"')
+                return f'https://github.com/{org}/{repo}/releases/latest/download/{file}'
             else:
-                return 'https://github.com/{org}/{repo}/releases/download/{version}/{file}'.format(
-                    repo=repo,
-                    file=file,
-                    version=version,
-                    org=org)
+                return f'https://github.com/{org}/{repo}/releases/download/{latest_version_tag}/{file}'
+        except:
+            # We use sys.exit(1) otherwise the mkdocs build doesn't
+            # fail on exceptions in macros
+            print_to_stdout(f'exception raised for {org}/{repo}/{file}\n', traceback.format_exc())
+            sys.exit(1)
+
+
 
     @env.macro
     def clientdocs():