Allow speculative run

Author: naveenOnarayanan

image/entrypoints/plan.sh

@@ -11,15 +11,22 @@ set-plan-args
 exec 3>&1
 
 ### Generate a plan
-PLAN_OUT="$STEP_TMP_DIR/plan.out"
+if [[ "$INPUT_SPECULATIVE" == "true" ]]; then
+    # Force speculative plan - no -out flag
+    PLAN_OUT=""
+else
+    # Normal behavior - try to save plan file
+    PLAN_OUT="$STEP_TMP_DIR/plan.out"
+fi
 PLAN_ARGS="$PLAN_ARGS -lock=false"
 plan
 
-if [[ $PLAN_EXIT -eq 1 ]]; then
+# If plan failed because remote backend doesn't support -out flag, retry without it
+# Skip this retry if we're already running speculative (PLAN_OUT is already empty)
+if [[ $PLAN_EXIT -eq 1 && -n "$PLAN_OUT" ]]; then
     if grep -q "Saving a generated plan is currently not supported" "$STEP_TMP_DIR/terraform_plan.stderr"; then
         # This terraform module is using the remote backend, which is deficient.
         PLAN_OUT=""
-        PLAN_ARGS="$PLAN_ARGS -lock=false"
         plan
     fi
 fi

terraform-plan/README.md

@@ -170,6 +170,24 @@ The [dflook/terraform-apply](https://github.com/dflook/terraform-github-actions/
   - Optional
   - Default: The Terraform default (10).
 
+* `speculative`
+
+  Set to `true` to force a speculative plan that cannot be applied.
+
+  This creates a "Planned and finished" run in Terraform Cloud instead of "Planned and saved".
+  Speculative plans don't lock state and can run in parallel with other operations.
+
+  This is useful for PR workflows where you want to preview changes without blocking other runs.
+
+  ```yaml
+  with:
+    speculative: true
+  ```
+
+  - Type: boolean
+  - Optional
+  - Default: `false`
+
 ## Outputs
 
 * `changes`
@@ -185,6 +203,8 @@ The [dflook/terraform-apply](https://github.com/dflook/terraform-github-actions/
 
   The plan can be used as the `plan_file` input to the [dflook/terraform-apply](https://github.com/dflook/terraform-github-actions/tree/main/terraform-apply) action.
 
+  This won't be set if `speculative` is `true` or if the backend type is `remote`/`cloud` in remote execution mode.
+
   Terraform plans often contain sensitive information, so this output should be treated with care.
 
   - Type: string

terraform-plan/action.yaml

@@ -78,6 +78,16 @@ inputs:
     description: Limit the number of concurrent operations
     required: false
     default: "0"
+  speculative:
+    description: |
+      Set to `true` to force a speculative plan that cannot be applied.
+
+      This creates a "Planned and finished" run in Terraform Cloud instead of "Planned and saved".
+      Speculative plans don't lock state and can run in parallel with other operations.
+
+      This is useful for PR workflows where you want to preview changes without blocking other runs.
+    required: false
+    default: "false"
 
 outputs:
   changes:
@@ -89,6 +99,8 @@ outputs:
 
       The plan can be used as the `plan_file` input to the [dflook/terraform-apply](https://github.com/dflook/terraform-github-actions/tree/main/terraform-apply) action.
 
+      This won't be set if `speculative` is `true` or if the backend type is `remote`/`cloud` in remote execution mode.
+
       Terraform plans often contain sensitive information, so this output should be treated with care.
   json_plan_path:
     description: |