Merge pull request #1271 from alixander/layoutplugin-panic

fix reparsing flags

ci/release/changelogs/next.md

@@ -19,3 +19,4 @@
 - Fixes rare panic exporting to gifs [#1257](https://github.com/terrastruct/d2/pull/1257)
 - Fixes bad performance in large grid diagrams [#1263](https://github.com/terrastruct/d2/pull/1263)
 - Fixes bug in ELK when container has ID "root" [#1268](https://github.com/terrastruct/d2/pull/1268)
+- Fixes edge case panic with invalid CLI arguments [#1271](https://github.com/terrastruct/d2/pull/1271)

d2plugin/serve.go

@@ -21,20 +21,22 @@ import (
 // Also see execPlugin in exec.go for the d2 binary plugin protocol.
 func Serve(p Plugin) xmain.RunFunc {
 	return func(ctx context.Context, ms *xmain.State) (err error) {
-		fs, err := p.Flags(ctx)
-		if err != nil {
-			return err
-		}
-		for _, f := range fs {
-			f.AddToOpts(ms.Opts)
-		}
-		err = ms.Opts.Flags.Parse(ms.Opts.Args)
-		if !errors.Is(err, pflag.ErrHelp) && err != nil {
-			return xmain.UsageErrorf("failed to parse flags: %v", err)
-		}
-		if errors.Is(err, pflag.ErrHelp) {
-			// At some point we want to write a friendly help.
-			return info(ctx, p, ms)
+		if !ms.Opts.Flags.Parsed() {
+			fs, err := p.Flags(ctx)
+			if err != nil {
+				return err
+			}
+			for _, f := range fs {
+				f.AddToOpts(ms.Opts)
+			}
+			err = ms.Opts.Flags.Parse(ms.Opts.Args)
+			if !errors.Is(err, pflag.ErrHelp) && err != nil {
+				return xmain.UsageErrorf("failed to parse flags: %v", err)
+			}
+			if errors.Is(err, pflag.ErrHelp) {
+				// At some point we want to write a friendly help.
+				return info(ctx, p, ms)
+			}
 		}
 
 		if len(ms.Opts.Flags.Args()) < 1 {

e2etests-cli/main_test.go

@@ -58,6 +58,14 @@ func TestCLI_E2E(t *testing.T) {
 				assert.Testdata(t, ".svg", svg)
 			},
 		},
+		{
+			name: "flags-panic",
+			run: func(t *testing.T, ctx context.Context, dir string, env *xos.Env) {
+				writeFile(t, dir, "hello-world.d2", `x -> y`)
+				err := runTestMain(t, ctx, dir, env, "layout", "dagre", "--dagre-nodesep", "50", "hello-world.d2")
+				assert.ErrorString(t, err, `failed to wait xmain test: e2etests-cli/d2: failed to unmarshal input to graph: `)
+			},
+		},
 		{
 			name: "empty-layer",
 			run: func(t *testing.T, ctx context.Context, dir string, env *xos.Env) {