CI: add Barnacle r: too-many-prs guard

Co-authored-by: Vincent Koc <vincentkoc@ieee.org>

.github/workflows/labeler.yml

@@ -201,6 +201,151 @@ jobs:
                 labels: [trustedLabel],
               });
             }
+      - name: Apply too-many-prs label
+        uses: actions/github-script@f28e40c7f34bde8b3046d885e986cb6290c5673b # v7
+        with:
+          github-token: ${{ steps.app-token.outputs.token || steps.app-token-fallback.outputs.token }}
+          script: |
+            const pullRequest = context.payload.pull_request;
+            if (!pullRequest) {
+              return;
+            }
+
+            const activePrLimitLabel = "r: too-many-prs";
+            const activePrLimit = 10;
+            const labelColor = "B60205";
+            const labelDescription = `Author has more than ${activePrLimit} active PRs in this repo`;
+            const authorLogin = pullRequest.user?.login;
+            if (!authorLogin) {
+              return;
+            }
+
+            const labelNames = new Set(
+              (pullRequest.labels ?? [])
+                .map((label) => (typeof label === "string" ? label : label?.name))
+                .filter((name) => typeof name === "string"),
+            );
+
+            const ensureLabelExists = async () => {
+              try {
+                await github.rest.issues.getLabel({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  name: activePrLimitLabel,
+                });
+              } catch (error) {
+                if (error?.status !== 404) {
+                  throw error;
+                }
+                await github.rest.issues.createLabel({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  name: activePrLimitLabel,
+                  color: labelColor,
+                  description: labelDescription,
+                });
+              }
+            };
+
+            const isPrivilegedAuthor = async () => {
+              if (pullRequest.author_association === "OWNER") {
+                return true;
+              }
+
+              let isMaintainer = false;
+              try {
+                const membership = await github.rest.teams.getMembershipForUserInOrg({
+                  org: context.repo.owner,
+                  team_slug: "maintainer",
+                  username: authorLogin,
+                });
+                isMaintainer = membership?.data?.state === "active";
+              } catch (error) {
+                if (error?.status !== 404) {
+                  throw error;
+                }
+              }
+
+              if (isMaintainer) {
+                return true;
+              }
+
+              try {
+                const permission = await github.rest.repos.getCollaboratorPermissionLevel({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  username: authorLogin,
+                });
+                const roleName = (permission?.data?.role_name ?? "").toLowerCase();
+                return roleName === "admin" || roleName === "maintain";
+              } catch (error) {
+                if (error?.status !== 404) {
+                  throw error;
+                }
+              }
+
+              return false;
+            };
+
+            if (await isPrivilegedAuthor()) {
+              if (labelNames.has(activePrLimitLabel)) {
+                try {
+                  await github.rest.issues.removeLabel({
+                    owner: context.repo.owner,
+                    repo: context.repo.repo,
+                    issue_number: pullRequest.number,
+                    name: activePrLimitLabel,
+                  });
+                } catch (error) {
+                  if (error?.status !== 404) {
+                    throw error;
+                  }
+                }
+              }
+              return;
+            }
+
+            let openPrCount = 0;
+            try {
+              const result = await github.rest.search.issuesAndPullRequests({
+                q: `repo:${context.repo.owner}/${context.repo.repo} is:pr is:open author:${authorLogin}`,
+                per_page: 1,
+              });
+              openPrCount = result?.data?.total_count ?? 0;
+            } catch (error) {
+              if (error?.status !== 422) {
+                throw error;
+              }
+              core.warning(`Skipping open PR count for ${authorLogin}; treating as 0.`);
+            }
+
+            if (openPrCount > activePrLimit) {
+              await ensureLabelExists();
+              if (!labelNames.has(activePrLimitLabel)) {
+                await github.rest.issues.addLabels({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  issue_number: pullRequest.number,
+                  labels: [activePrLimitLabel],
+                });
+              }
+              return;
+            }
+
+            if (labelNames.has(activePrLimitLabel)) {
+              try {
+                await github.rest.issues.removeLabel({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  issue_number: pullRequest.number,
+                  name: activePrLimitLabel,
+                });
+              } catch (error) {
+                if (error?.status !== 404) {
+                  throw error;
+                }
+              }
+            }
 
   backfill-pr-labels:
     if: github.event_name == 'workflow_dispatch'