get rid of EvalEarlyExitError

This was mostly unused now, since we no longer needed to interrupt a
series of eval node executions.

The exception was the stopHook, which is still used to halt execution
when there's an interrupt. Since interrupting execution should not
complete successfully, we use a normal opaque error to halt everything,
and return it to the UI.

We can work on coalescing or hiding these if necessary in a separate PR.

terraform/context_apply_test.go

@@ -1734,8 +1734,16 @@ func TestContext2Apply_cancel(t *testing.T) {
 	}()
 
 	state := <-stateCh
-	if applyDiags.HasErrors() {
-		t.Fatalf("unexpected errors: %s", applyDiags.Err())
+	// only expecting an early exit error
+	if !applyDiags.HasErrors() {
+		t.Fatal("expected early exit error")
+	}
+
+	for _, d := range applyDiags {
+		desc := d.Description()
+		if desc.Summary != "execution halted" {
+			t.Fatalf("unexpected error: %v", applyDiags.Err())
+		}
 	}
 
 	actual := strings.TrimSpace(state.String())
@@ -1812,8 +1820,16 @@ func TestContext2Apply_cancelBlock(t *testing.T) {
 
 	// Wait for apply to complete
 	state := <-stateCh
-	if applyDiags.HasErrors() {
-		t.Fatalf("unexpected error: %s", applyDiags.Err())
+	// only expecting an early exit error
+	if !applyDiags.HasErrors() {
+		t.Fatal("expected early exit error")
+	}
+
+	for _, d := range applyDiags {
+		desc := d.Description()
+		if desc.Summary != "execution halted" {
+			t.Fatalf("unexpected error: %v", applyDiags.Err())
+		}
 	}
 
 	checkStateString(t, state, `
@@ -1882,7 +1898,18 @@ func TestContext2Apply_cancelProvisioner(t *testing.T) {
 
 	// Wait for completion
 	state := <-stateCh
-	assertNoErrors(t, applyDiags)
+
+	// we are expecting only an early exit error
+	if !applyDiags.HasErrors() {
+		t.Fatal("expected early exit error")
+	}
+
+	for _, d := range applyDiags {
+		desc := d.Description()
+		if desc.Summary != "execution halted" {
+			t.Fatalf("unexpected error: %v", applyDiags.Err())
+		}
+	}
 
 	checkStateString(t, state, `
 aws_instance.foo: (tainted)

terraform/eval_context_builtin.go

@@ -107,7 +107,7 @@ func (ctx *BuiltinEvalContext) Hook(fn func(Hook) (HookAction, error)) error {
 		case HookActionHalt:
 			// Return an early exit error to trigger an early exit
 			log.Printf("[WARN] Early exit triggered by hook: %T", h)
-			return EvalEarlyExitError{}
+			return nil
 		}
 	}
 

terraform/eval_error.go

@@ -1,7 +0,0 @@
-package terraform
-
-// EvalEarlyExitError is a special error return value that can be returned
-// by eval nodes that does an early exit.
-type EvalEarlyExitError struct{}
-
-func (EvalEarlyExitError) Error() string { return "early exit" }

terraform/graph_walk_context.go

@@ -2,7 +2,6 @@ package terraform
 
 import (
 	"context"
-	"errors"
 	"sync"
 
 	"github.com/zclconf/go-cty/cty"
@@ -36,7 +35,6 @@ type ContextGraphWalker struct {
 	// is in progress.
 	NonFatalDiagnostics tfdiags.Diagnostics
 
-	errorLock          sync.Mutex
 	once               sync.Once
 	contexts           map[string]*BuiltinEvalContext
 	contextLock        sync.Mutex
@@ -124,46 +122,7 @@ func (w *ContextGraphWalker) init() {
 func (w *ContextGraphWalker) Execute(ctx EvalContext, n GraphNodeExecutable) tfdiags.Diagnostics {
 	// Acquire a lock on the semaphore
 	w.Context.parallelSem.Acquire()
+	defer w.Context.parallelSem.Release()
 
-	diags := n.Execute(ctx, w.Operation)
-
-	// Release the semaphore
-	w.Context.parallelSem.Release()
-
-	if !diags.HasErrors() {
-		return diags
-	}
-
-	// Acquire the lock because anything is going to require a lock.
-	w.errorLock.Lock()
-	defer w.errorLock.Unlock()
-
-	err := diags.Err()
-	// Handle a simple early exit error
-	if errors.Is(err, EvalEarlyExitError{}) {
-		return nil
-	}
-
-	// we need to see if this wraps only EarlyExitErrors
-	if wrapper, ok := err.(interface{ WrappedErrors() []error }); ok {
-		//WrappedErrors only returns native error values, so we can't extract
-		//them from diagnostics. Just return the whole thing if we have a
-		//combination.
-		errs := wrapper.WrappedErrors()
-		earlyExit := true
-		for _, err := range errs {
-			if err != (EvalEarlyExitError{}) {
-				earlyExit = false
-			}
-		}
-		if len(errs) > 0 && earlyExit {
-			return nil
-		}
-	}
-
-	// Otherwise, we'll let our usual diagnostics machinery figure out how to
-	// unpack this as one or more diagnostic messages and return that. If we
-	// get down here then the returned diagnostics will contain at least one
-	// error, causing the graph walk to halt.
-	return diags
+	return n.Execute(ctx, w.Operation)
 }

terraform/hook_stop.go

@@ -1,6 +1,7 @@
 package terraform
 
 import (
+	"errors"
 	"sync/atomic"
 
 	"github.com/zclconf/go-cty/cty"
@@ -76,11 +77,7 @@ func (h *stopHook) PostStateUpdate(new *states.State) (HookAction, error) {
 
 func (h *stopHook) hook() (HookAction, error) {
 	if h.Stopped() {
-		// FIXME: This should really return an error since stopping partway
-		// through is not a successful run-to-completion, but we'll need to
-		// introduce that cautiously since existing automation solutions may
-		// be depending on this behavior.
-		return HookActionHalt, nil
+		return HookActionHalt, errors.New("execution halted")
 	}
 
 	return HookActionContinue, nil

terraform/node_resource_apply_instance.go

@@ -148,7 +148,6 @@ func (n *NodeApplyableResourceInstance) dataResourceExecute(ctx EvalContext) (di
 	}
 	// Stop early if we don't actually have a diff
 	if change == nil {
-		diags = diags.Append(EvalEarlyExitError{})
 		return diags
 	}
 
@@ -223,7 +222,6 @@ func (n *NodeApplyableResourceInstance) managedResourceExecute(ctx EvalContext)
 	// We don't want to do any destroys
 	// (these are handled by NodeDestroyResourceInstance instead)
 	if diffApply == nil || diffApply.Action == plans.Delete {
-		diags = diags.Append(EvalEarlyExitError{})
 		return diags
 	}
 
@@ -325,7 +323,6 @@ func (n *NodeApplyableResourceInstance) managedResourceExecute(ctx EvalContext)
 	// into a NoOp if it only requires destroying, since destroying
 	// is handled by NodeDestroyResourceInstance.
 	if diffApply == nil || diffApply.Action == plans.NoOp {
-		diags = diags.Append(EvalEarlyExitError{})
 		return diags
 	}
 

terraform/node_resource_destroy.go

@@ -163,7 +163,6 @@ func (n *NodeDestroyResourceInstance) Execute(ctx EvalContext, op walkOperation)
 	// EvalReduceDiff may have simplified our planned change
 	// into a NoOp if it does not require destroying.
 	if changeApply == nil || changeApply.Action == plans.NoOp {
-		diags = diags.Append(EvalEarlyExitError{})
 		return diags
 	}
 
@@ -175,7 +174,6 @@ func (n *NodeDestroyResourceInstance) Execute(ctx EvalContext, op walkOperation)
 
 	// Exit early if the state object is null after reading the state
 	if state == nil || state.Value.IsNull() {
-		diags = diags.Append(EvalEarlyExitError{})
 		return diags
 	}