Add workflow to check PR titles & descriptions

.github/workflows/pr-text-checker.yaml

@@ -0,0 +1,93 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Check the subject and description of each PR for basic best practices and
+# fail with an error if a PR doesn't meet the conditions.
+
+name: Pull request text checker
+run-name: >-
+  Check title and description of PR
+  #${{github.event.inputs.pr-number || github.event.pull_request.number}}
+  by ${{github.actor}}
+
+on:
+  pull_request:
+    types:
+      - opened
+      - reopened
+      - synchronize
+    branches:
+      - main
+
+  workflow_dispatch:
+    inputs:
+      pr-number:
+        description: 'The PR number of the PR to check:'
+        type: string
+        required: true
+      debug:
+        description: 'Run with debugging options'
+        type: boolean
+        default: true
+
+permissions: read-all
+
+jobs:
+  check-pr-text:
+    name: "Title & description check"
+    if: github.repository_owner == 'quantumlib'
+    runs-on: ubuntu-slim
+    timeout-minutes: 5
+    steps:
+      - name: Enable shell debugging if requested
+        if: ${{inputs.debug || runner.debug}}
+        run: echo "SHELLOPTS=xtrace" >> "${GITHUB_ENV}"
+
+      # Note that this workflow does not need to check out the git repo because
+      # it does not need to read any files in the repo.
+      - name: Check title and description
+        run: |
+          pr_title=$(jq -r ".pull_request.title" "${GITHUB_EVENT_PATH}")
+          pr_body=$(jq -r ".pull_request.body" "${GITHUB_EVENT_PATH}")
+
+          declare -a problems=()
+          if [[ -z "${pr_title}" ]]; then
+            problems+=("PR title cannot be empty.")
+          else
+            read -ra title_words <<< "${pr_title}"
+            if [[ ${#title_words[@]} -lt 2 ]]; then
+              problems+=("PR title must contain at least two words.")
+            fi
+          fi
+
+          if [[ -z "${pr_body}" || ${#pr_body} -lt 10 ]]; then
+            problems+=("PR description must be at least 10 characters long.")
+          fi
+
+          if [[ ${#problems[@]} -gt 0 ]]; then
+            # shellcheck disable=SC2034
+            {
+              echo "Please fix the following problem(s) with this PR:"
+              printf -- ":x:  %s\n" "${problems[@]}"
+            } >> "${GITHUB_STEP_SUMMARY}"
+          fi
+
+      # Point people to the list of problems. Done as a separate step to make
+      # this text easier for people to find in the workflow results.
+      - name: Report outcome
+        run: |
+          if [[ "${result}" == "error" ]]; then
+            echo '::error::Failed checks. Please check the workflow summary.'
+            exit 1
+          fi