Merge pull request #202 from dflook/large-plan

Truncate large plans in PR comments

Author: dflook

.github/workflows/test-apply.yaml

@@ -841,7 +841,7 @@ jobs:
       - name: Plan
         uses: ./terraform-plan
         with:
-          label: test-apply warnings (hash)
+          label: test-apply warnings_hash
           path: tests/workflows/test-apply/warnings
 
       - name: Create warning
@@ -851,7 +851,7 @@ jobs:
       - name: Apply
         uses: ./terraform-apply
         with:
-          label: test-apply warnings (hash)
+          label: test-apply warnings_hash
           path: tests/workflows/test-apply/warnings
 
   warnings_text:
@@ -866,7 +866,7 @@ jobs:
       - name: Plan
         uses: dflook/terraform-plan@v1.22.2
         with:
-          label: test-apply warnings (text)
+          label: test-apply warnings_text
           path: tests/workflows/test-apply/warnings
 
       - name: Create warning
@@ -876,5 +876,63 @@ jobs:
       - name: Apply
         uses: ./terraform-apply
         with:
-          label: test-apply warnings (text)
+          label: test-apply warnings_text
           path: tests/workflows/test-apply/warnings
+
+  long_plan:
+    runs-on: ubuntu-latest
+    name: Apply a plan that doesn't fit in a comment
+    env:
+      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Plan
+        uses: ./terraform-plan
+        with:
+          label: test-apply long_plan
+          path: tests/workflows/test-apply/long_plan
+
+      - name: Apply
+        uses: ./terraform-apply
+        with:
+          label: test-apply long_plan
+          path: tests/workflows/test-apply/long_plan
+
+  long_plan_changes:
+    runs-on: ubuntu-latest
+    name: Don't apply a changed plan that doesn't fit in a comment
+    env:
+      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Plan
+        uses: ./terraform-plan
+        with:
+          label: test-apply long_plan_changes
+          path: tests/workflows/test-apply/long_plan
+
+      - name: Apply
+        uses: ./terraform-apply
+        id: apply
+        continue-on-error: true
+        with:
+          label: test-apply long_plan_changes
+          path: tests/workflows/test-apply/long_plan
+          variables: |
+              length = 2
+
+      - name: Check failed to apply
+        run: |
+          if [[ "${{ steps.apply.outcome }}" != "failure" ]]; then
+            echo "Apply did not fail correctly"
+            exit 1
+          fi
+
+          if [[ "${{ steps.apply.outputs.failure-reason }}" != "plan-changed" ]]; then
+            echo "::error:: failure-reason not set correctly"
+            exit 1
+          fi

image/src/github_pr_comment/__main__.py

@@ -5,7 +5,7 @@
 import re
 import sys
 from pathlib import Path
-from typing import (NewType, Optional, cast)
+from typing import (NewType, Optional, cast, Tuple)
 
 import canonicaljson
 
@@ -235,6 +235,34 @@ def is_approved(proposed_plan: str, comment: TerraformComment) -> bool:
         debug('Approving plan based on plan text')
         return plan_cmp(proposed_plan, comment.body)
 
+def format_plan_text(plan_text: str) -> Tuple[str, str]:
+    """
+    Format the given plan for insertion into a PR comment
+    """
+
+    max_body_size = 50000  # bytes
+
+    def truncate(t):
+        lines = []
+        total_size = 0
+
+        for line in t.splitlines():
+            line_size = len(line.encode()) + 1  # + newline
+            if total_size + line_size > max_body_size:
+                lines.append('Plan is too large to fit in a PR comment. See the full plan in the workflow log.')
+                break
+
+            lines.append(line)
+            total_size += line_size
+
+        return '\n'.join(lines)
+
+    if len(plan_text.encode()) > max_body_size:
+        # needs truncation
+        return 'trunc', truncate(plan_text)
+    else:
+        return 'text', plan_text
+
 def main() -> int:
     if len(sys.argv) < 2:
         sys.stderr.write(f'''Usage:
@@ -274,14 +302,15 @@ def main() -> int:
         headers = comment.headers.copy()
         headers['plan_job_ref'] = job_workflow_ref()
         headers['plan_hash'] = plan_hash(body, comment.issue_url)
+        headers['plan_text_format'], plan_text = format_plan_text(body)
 
         comment = update_comment(
             github,
             comment,
             description=description,
             summary=create_summary(body),
             headers=headers,
-            body=body,
+            body=plan_text,
             status=status
         )
 
@@ -316,23 +345,29 @@ def main() -> int:
             sys.stdout.write("The plan on the PR must be up to date. Alternatively, set the auto_approve input to 'true' to apply outdated plans\n")
             comment = update_comment(github, comment, status=f':x: Plan not applied in {job_markdown_ref()} (Plan has changed)')
 
-            sys.stdout.write("""Performing diff between the pull request plan and the plan generated at execution time ...
-> are lines from the plan in the pull request
-< are lines from the plan generated at execution
-Plan changes:
-""")
-
             approved_plan_path = os.path.join(os.environ['STEP_TMP_DIR'], 'approved-plan.txt')
             with open(approved_plan_path, 'w') as f:
                 f.write(comment.body.strip())
             proposed_plan_path = os.path.join(os.environ['STEP_TMP_DIR'], 'proposed-plan.txt')
             with open(proposed_plan_path, 'w') as f:
-                f.write(proposed_plan.strip())
+                _, formatted_proposed_plan = format_plan_text(proposed_plan.strip())
+                f.write(formatted_proposed_plan.strip())
+
             debug(f'diff {proposed_plan_path} {approved_plan_path}')
             diff_complete = subprocess.run(['diff', proposed_plan_path, approved_plan_path], check=False, capture_output=True, encoding='utf-8')
             sys.stdout.write(diff_complete.stdout)
             sys.stderr.write(diff_complete.stderr)
 
+            if diff_complete.returncode != 0:
+                sys.stdout.write("""Performing diff between the pull request plan and the plan generated at execution time.
+> are lines from the plan in the pull request
+< are lines from the plan generated at execution
+Plan differences:
+""")
+
+            if comment.headers.get('plan_text_format', 'text') == 'trunc':
+                sys.stdout.write('\nThe plan text was too large for a PR comment, not all differences may be shown here.')
+
             if plan_ref := comment.headers.get('plan_job_ref'):
                 sys.stdout.write(f'\nCompare with the plan generated by the dflook/terraform-plan action in {plan_ref}\n')
 

image/src/github_pr_comment/hash.py

@@ -18,7 +18,7 @@ def plan_hash(plan_text: str, salt: str) -> str:
     TODO: Change to use the plan json output
     """
 
-    debug(f'Hashing with salt {salt} and plan:\n{plan_text}')
+    debug(f'Hashing with salt {salt}')
 
     plan = remove_warnings(remove_unchanged_attributes(plan_text))
 

tests/workflows/test-apply/long_plan/main.tf

@@ -0,0 +1,14 @@
+resource "random_id" "a" {
+  count = 250
+
+  byte_length = 3
+}
+
+resource "random_id" "b" {
+  byte_length = var.length
+}
+
+variable "length" {
+  type = number
+  default = 3
+}