backend/local: Return diag for refresh empty state

The warning diag added when refreshing an empty state file was never
rendered, and instead a custom (and incorrect) warning was output to the
UI. This commit fixes the dropped diag and removes the custom warning.

backend/local/backend_refresh.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"log"
 	"os"
-	"strings"
 
 	"github.com/hashicorp/errwrap"
 	"github.com/hashicorp/terraform/backend"
@@ -66,14 +65,11 @@ func (b *Local) opRefresh(
 	// Set our state
 	runningOp.State = opState.State()
 	if !runningOp.State.HasResources() {
-		if b.CLI != nil {
-			diags = diags.Append(tfdiags.Sourceless(
-				tfdiags.Warning,
-				"Empty or non-existent state",
-				"There are currently no resources tracked in the state, so there is nothing to refresh.",
-			))
-			b.CLI.Output(b.Colorize().Color(strings.TrimSpace(refreshNoState) + "\n"))
-		}
+		diags = diags.Append(tfdiags.Sourceless(
+			tfdiags.Warning,
+			"Empty or non-existent state",
+			"There are currently no resources tracked in the state, so there is nothing to refresh.",
+		))
 	}
 
 	// Perform the refresh in a goroutine so we can be interrupted
@@ -90,7 +86,7 @@ func (b *Local) opRefresh(
 		return
 	}
 
-	// write the resulting state to the running op
+	// Write the resulting state to the running op
 	runningOp.State = newState
 	diags = diags.Append(refreshDiags)
 	if refreshDiags.HasErrors() {
@@ -104,12 +100,7 @@ func (b *Local) opRefresh(
 		op.ReportResult(runningOp, diags)
 		return
 	}
+
+	// Show any remaining warnings before exiting
+	op.ReportResult(runningOp, diags)
 }
-
-const refreshNoState = `
-[reset][bold][yellow]Empty or non-existent state file.[reset][yellow]
-
-Refresh will do nothing. Refresh does not error or return an erroneous
-exit status because many automation scripts use refresh, plan, then apply
-and may not have a state file yet for the first run.
-`

backend/local/backend_refresh_test.go

@@ -3,6 +3,7 @@ package local
 import (
 	"context"
 	"fmt"
+	"strings"
 	"testing"
 
 	"github.com/hashicorp/terraform/addrs"
@@ -214,6 +215,42 @@ func TestLocal_refresh_context_error(t *testing.T) {
 	assertBackendStateUnlocked(t, b)
 }
 
+func TestLocal_refreshEmptyState(t *testing.T) {
+	b, cleanup := TestLocal(t)
+	defer cleanup()
+
+	p := TestLocalProvider(t, b, "test", refreshFixtureSchema())
+	testStateFile(t, b.StatePath, states.NewState())
+
+	p.ReadResourceFn = nil
+	p.ReadResourceResponse = &providers.ReadResourceResponse{NewState: cty.ObjectVal(map[string]cty.Value{
+		"id": cty.StringVal("yes"),
+	})}
+
+	op, configCleanup := testOperationRefresh(t, "./testdata/refresh")
+	defer configCleanup()
+
+	record, playback := testRecordDiagnostics(t)
+	op.ShowDiagnostics = record
+
+	run, err := b.Operation(context.Background(), op)
+	if err != nil {
+		t.Fatalf("bad: %s", err)
+	}
+	<-run.Done()
+
+	diags := playback()
+	if diags.HasErrors() {
+		t.Fatalf("expected only warning diags, got errors: %s", diags.Err())
+	}
+	if got, want := diags.ErrWithWarnings().Error(), "Empty or non-existent state"; !strings.Contains(got, want) {
+		t.Errorf("wrong diags\n got: %s\nwant: %s", got, want)
+	}
+
+	// the backend should be unlocked after a run
+	assertBackendStateUnlocked(t, b)
+}
+
 func testOperationRefresh(t *testing.T, configDir string) (*backend.Operation, func()) {
 	t.Helper()