ci(sdks): Warn against non-trivial changes to multiple SDKs

Add a CI job which fails and posts a comment when non-trivial changes to multiple SDK docs pages are detected. We define non-trivial as affecting more than five lines.

We do not intend to make this CI job required; rather, I hope PR authors and reviewers will heed the comments posted by this workflow.

Author: szokeasaurusrex

.github/workflows/enforce-single-sdk-changes.yml

@@ -0,0 +1,88 @@
+name: Enforce Single SDK Changes
+
+on:
+  pull_request:
+    paths:
+      - 'docs/platforms/**'
+      - 'platform-includes/**'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  check-sdk-diff-scope:
+    name: Check SDK diff scope
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      pull-requests: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+        with:
+          fetch-depth: 0
+
+      - name: Compute diff and evaluate
+        id: evaluate
+        run: |
+          set +e
+          SDK_LIST=$(git diff --numstat origin/${{ github.base_ref }}...HEAD | bun scripts/check-sdk-diff-scope.ts)
+          if [ $? -ne 0 ]; then
+            echo "violation=true" >> "$GITHUB_OUTPUT"
+            echo "sdk_list=$SDK_LIST" >> "$GITHUB_OUTPUT"
+          else
+            echo "violation=false" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Post, update, or delete PR comment
+        uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd # v8.0.0
+        with:
+          script: |
+            const MARKER = '<!-- enforce-single-sdk-changes -->';
+            const violation = '${{ steps.evaluate.outputs.violation }}' === 'true';
+
+            const {data: comments} = await github.rest.issues.listComments({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.issue.number,
+            });
+            const existing = comments.find(c => c.body.includes(MARKER));
+
+            if (violation) {
+              const sdkList = ${{ toJSON(steps.evaluate.outputs.sdk_list) }};
+              const body = `${MARKER}
+            ### 🚫 Non-trivial changes to multiple SDKs
+
+            This PR contains non-trivial changes to multiple SDKs: ${sdkList}.
+            Changes to multiple SDKs should be submitted as separate PRs: **one PR per SDK**.
+
+            Please **split this PR** accordingly. Thank you in advance! 🙏`;
+
+              if (existing && existing.body !== body) {
+                await github.rest.issues.updateComment({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  comment_id: existing.id,
+                  body,
+                });
+              } else if (!existing) {
+                await github.rest.issues.createComment({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  issue_number: context.issue.number,
+                  body,
+                });
+              }
+            } else if (existing) {
+              await github.rest.issues.deleteComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                comment_id: existing.id,
+              });
+            }
+
+      - name: Fail check
+        if: steps.evaluate.outputs.violation == 'true'
+        run: exit 1

scripts/check-sdk-diff-scope.ts

@@ -0,0 +1,64 @@
+#!/usr/bin/env bun
+/**
+ * Enforces the policy that a single PR should only contain non-trivial changes
+ * to one SDK at a time. PRs spanning multiple SDKs are harder to review and
+ * increase the risk of inconsistencies between platforms.
+ *
+ * Reads `git diff --numstat` from stdin (one `<added>\t<deleted>\t<path>` line
+ * per changed file) and attributes each file to an SDK. If the total lines
+ * changed for at least MIN_VIOLATING_SDKS SDKs each exceed LINE_THRESHOLD,
+ * the script prints the violating SDK list and exits 1.
+ *
+ * Used in CI as:
+ *   git diff --numstat origin/$BASE...HEAD | bun scripts/check-sdk-diff-scope.ts
+ */
+
+/** SDKs with fewer total changed lines than this are ignored (e.g. a one-line typo fix that touches two SDKs should not block the PR). */
+const LINE_THRESHOLD = 5;
+/** Minimum number of SDKs that must exceed LINE_THRESHOLD for the check to fail. */
+const MIN_VIOLATING_SDKS = 2;
+
+/**
+ * Extracts the SDK name from a changed file path, or returns null if the
+ * file is not attributed to any SDK.
+ *
+ * Two path patterns are recognised:
+ *   - docs/platforms/<sdk>/...          → sdk is the first path segment after platforms/
+ *   - platform-includes/.../<sdk>.<variant>.mdx → sdk is the first dot-segment of the filename
+ *     e.g. `javascript.angular.mdx` → `javascript`, `react-native.mdx` → `react-native`
+ */
+function sdkForPath(path: string): string | null {
+  const segs = path.split("/");
+  if (segs[0] === "docs" && segs[1] === "platforms") {
+    return segs[2] ?? null;
+  }
+  if (segs[0] === "platform-includes") {
+    return segs.at(-1)!.split(".")[0];
+  }
+  return null;
+}
+
+// Accumulate total lines changed (added + deleted) per SDK.
+const sdkLines = new Map<string, number>();
+
+const input = await Bun.stdin.text();
+for (const line of input.split("\n")) {
+  const [added, deleted, path] = line.split("\t");
+  if (!path || added === "-") continue; // binary file or empty line
+  const sdk = sdkForPath(path.trim());
+  if (sdk) {
+    sdkLines.set(sdk, (sdkLines.get(sdk) ?? 0) + +added + +deleted);
+  }
+}
+
+// Collect SDKs that exceed the line threshold, ignoring trivial touches.
+const violating = [...sdkLines.entries()]
+  .filter(([, n]) => n >= LINE_THRESHOLD)
+  .map(([sdk]) => sdk)
+  .sort();
+
+if (violating.length >= MIN_VIOLATING_SDKS) {
+  // Print the list for the CI step to capture and include in the PR comment.
+  console.log(violating.map(s => `\`${s}\``).join(", "));
+  process.exit(1);
+}