ci(terraform): fail mixed app and Terraform changes

.github/workflows/ci-terraform.yaml

@@ -10,6 +10,16 @@ name: CI — Terraform
 #       uses: Sea-Haven-Industries/.github/.github/workflows/ci-terraform.yaml@<sha> # vX.Y.Z
 #       with:
 #         terraform-version: "1.16.0"
+#         app-paths: |
+#           src/
+#           package.json
+#           package-lock.json
+#
+# app-paths is optional. Empty skips isolation and leaves fmt/init/validate
+# unchanged. A trailing slash is a directory prefix. Any other line is an
+# exact file. pull_request classifies the merge-base of the base SHA to HEAD.
+# merge_group classifies each first-parent commit against its parent, so a
+# Terraform-only PR stacked with an app-only PR still passes.
 
 on:
   workflow_call:
@@ -22,6 +32,10 @@ on:
         description: "Directory containing Terraform sources"
         type: string
         default: "terraform"
+      app-paths:
+        description: "Newline-separated deployable paths. A trailing slash is a prefix. Any other entry is an exact file. Empty skips isolation."
+        type: string
+        default: ""
 
 permissions:
   contents: read
@@ -41,6 +55,7 @@ jobs:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           persist-credentials: false
+          fetch-depth: 0
 
       - uses: hashicorp/setup-terraform@dfe3c3f87815947d99a8997f908cb6525fc44e9e # v4.0.1
         with:
@@ -55,3 +70,50 @@ jobs:
 
       - name: Terraform validate
         run: terraform validate
+
+      - name: Checkout isolation checker
+        if: inputs.app-paths != ''
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          repository: Sea-Haven-Industries/.github
+          ref: ${{ github.workflow_sha }}
+          path: .ci-org-github
+          persist-credentials: false
+
+      - name: App and Terraform isolation
+        if: inputs.app-paths != ''
+        working-directory: ${{ github.workspace }}
+        env:
+          APP_PATHS: ${{ inputs.app-paths }}
+          EVENT_NAME: ${{ github.event_name }}
+          PR_BASE_SHA: ${{ github.event.pull_request.base.sha }}
+          MERGE_GROUP_BASE_SHA: ${{ github.event.merge_group.base_sha }}
+          CHECKER: ${{ github.workspace }}/.ci-org-github/scripts/check_app_terraform_isolation.py
+        run: |
+          set -euo pipefail
+          classify() {
+            python3 "${CHECKER}"
+          }
+          case "${EVENT_NAME}" in
+            pull_request)
+              if [[ -z "${PR_BASE_SHA}" ]]; then
+                echo "FAIL: pull_request base SHA is empty" >&2
+                exit 1
+              fi
+              merge_base="$(git merge-base "${PR_BASE_SHA}" HEAD)"
+              git diff --name-only --diff-filter=ACMR "${merge_base}" HEAD | classify
+              ;;
+            merge_group)
+              if [[ -z "${MERGE_GROUP_BASE_SHA}" ]]; then
+                echo "FAIL: merge_group base SHA is empty" >&2
+                exit 1
+              fi
+              while IFS= read -r sha; do
+                [[ -z "${sha}" ]] && continue
+                git diff --name-only --diff-filter=ACMR "${sha}^" "${sha}" | classify
+              done < <(git rev-list --reverse --first-parent "${MERGE_GROUP_BASE_SHA}..HEAD")
+              ;;
+            *)
+              echo "SKIP: live isolation runs on pull_request and merge_group (event: ${EVENT_NAME})"
+              ;;
+          esac

.github/workflows/ci.yaml

@@ -53,6 +53,10 @@ jobs:
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
 
+      - name: Isolation checker tests
+        run: python3 scripts/test_check_app_terraform_isolation.py
+        shell: bash
+
       - name: Install actionlint
         env:
           ACTIONLINT_VERSION: 1.7.12

scripts/check_app_terraform_isolation.py

@@ -0,0 +1,96 @@
+#!/usr/bin/env python3
+"""Fail when a change set mixes Terraform with deployable application files.
+
+APP_PATHS is newline-separated. A trailing slash is a directory prefix.
+Any other entry is an exact file. Paths that are not listed are neutral, so
+workflows, docs, and tests may travel with either side. An empty APP_PATHS
+skips the check.
+"""
+
+from __future__ import annotations
+
+import argparse
+import os
+import sys
+
+
+def parse_app_rules(raw: str) -> tuple[frozenset[str], frozenset[str]]:
+    prefixes: set[str] = set()
+    exact: set[str] = set()
+    for line in raw.splitlines():
+        item = line.strip().replace("\\", "/")
+        if not item or item.startswith("#"):
+            continue
+        if item.endswith("/"):
+            prefixes.add(item)
+        else:
+            exact.add(item)
+    return frozenset(prefixes), frozenset(exact)
+
+
+def is_terraform_path(path: str) -> bool:
+    normalized = path.replace("\\", "/")
+    return normalized == "terraform" or normalized.startswith("terraform/")
+
+
+def is_app_path(path: str, prefixes: frozenset[str], exact: frozenset[str]) -> bool:
+    normalized = path.replace("\\", "/")
+    if normalized in exact:
+        return True
+    for prefix in prefixes:
+        if normalized.startswith(prefix) or f"{normalized}/" == prefix:
+            return True
+    return False
+
+
+def isolation_violation(
+    paths: list[str], app_paths: str
+) -> tuple[list[str], list[str]] | None:
+    prefixes, exact = parse_app_rules(app_paths)
+    if not prefixes and not exact:
+        return None
+    terraform_files = sorted({path for path in paths if is_terraform_path(path)})
+    app_files = sorted({path for path in paths if is_app_path(path, prefixes, exact)})
+    if terraform_files and app_files:
+        return terraform_files, app_files
+    return None
+
+
+def first_isolation_violation(
+    file_sets: list[list[str]], app_paths: str
+) -> tuple[list[str], list[str]] | None:
+    for paths in file_sets:
+        violation = isolation_violation(paths, app_paths)
+        if violation is not None:
+            return violation
+    return None
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "paths",
+        nargs="*",
+        help="Changed paths. Omit and pass newline-separated paths on stdin.",
+    )
+    args = parser.parse_args()
+    paths = list(args.paths)
+    if not paths and not sys.stdin.isatty():
+        paths = [line.strip() for line in sys.stdin if line.strip()]
+    violation = isolation_violation(paths, os.environ.get("APP_PATHS", ""))
+    if violation is None:
+        print("PASS: application and Terraform changes are isolated")
+        return 0
+    terraform_files, app_files = violation
+    print("FAIL: do not mix deployable application files with terraform/", file=sys.stderr)
+    print("terraform:", file=sys.stderr)
+    for path in terraform_files:
+        print(f"  {path}", file=sys.stderr)
+    print("application:", file=sys.stderr)
+    for path in app_files:
+        print(f"  {path}", file=sys.stderr)
+    return 1
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())

scripts/test_check_app_terraform_isolation.py

@@ -0,0 +1,81 @@
+#!/usr/bin/env python3
+"""Tests for check_app_terraform_isolation."""
+
+from __future__ import annotations
+
+import unittest
+
+from check_app_terraform_isolation import first_isolation_violation, isolation_violation
+
+APP_PATHS = "src/\npackage.json\npackage-lock.json\n"
+
+
+class IsolationTests(unittest.TestCase):
+    def test_terraform_only(self) -> None:
+        self.assertIsNone(
+            isolation_violation(
+                ["terraform/lambda.tf", "terraform/README.md"],
+                APP_PATHS,
+            )
+        )
+
+    def test_app_only(self) -> None:
+        self.assertIsNone(
+            isolation_violation(
+                ["src/processPaymentCsv.js", "package.json", "package-lock.json"],
+                APP_PATHS,
+            )
+        )
+
+    def test_docs_and_workflows_with_terraform(self) -> None:
+        self.assertIsNone(
+            isolation_violation(
+                [
+                    "terraform/lambda.tf",
+                    ".github/workflows/deploy.yaml",
+                    "SETUP.md",
+                    "scripts/check_app_terraform_isolation.py",
+                ],
+                APP_PATHS,
+            )
+        )
+
+    def test_mixed_app_and_terraform_fails(self) -> None:
+        violation = isolation_violation(
+            ["terraform/lambda.tf", "src/processPaymentCsv.js", "package.json"],
+            APP_PATHS,
+        )
+        self.assertIsNotNone(violation)
+        terraform_files, app_files = violation or ([], [])
+        self.assertEqual(terraform_files, ["terraform/lambda.tf"])
+        self.assertEqual(app_files, ["package.json", "src/processPaymentCsv.js"])
+
+    def test_empty_app_paths_skips(self) -> None:
+        self.assertIsNone(
+            isolation_violation(
+                ["terraform/lambda.tf", "src/processPaymentCsv.js"],
+                "",
+            )
+        )
+
+    def test_separate_commits_pass_when_classified_alone(self) -> None:
+        self.assertIsNone(
+            first_isolation_violation(
+                [
+                    ["terraform/lambda.tf"],
+                    ["src/processPaymentCsv.js"],
+                ],
+                APP_PATHS,
+            )
+        )
+
+    def test_union_of_separate_commits_fails(self) -> None:
+        violation = isolation_violation(
+            ["terraform/lambda.tf", "src/processPaymentCsv.js"],
+            APP_PATHS,
+        )
+        self.assertIsNotNone(violation)
+
+
+if __name__ == "__main__":
+    unittest.main()