cmd/evm: add --ndjson flag for streaming JSON output

cmd/evm/blockrunner.go

@@ -42,6 +42,7 @@ var blockTestCommand = &cli.Command{
 	Flags: slices.Concat([]cli.Flag{
 		DumpFlag,
 		HumanReadableFlag,
+		NDJSONFlag,
 		RunFlag,
 		WitnessCrossCheckFlag,
 		FuzzFlag,

cmd/evm/enginerunner.go

@@ -51,6 +51,7 @@ var engineTestCommand = &cli.Command{
 	Flags: slices.Concat([]cli.Flag{
 		DumpFlag,
 		HumanReadableFlag,
+		NDJSONFlag,
 		RunFlag,
 		FuzzFlag,
 		WorkersFlag,

cmd/evm/main.go

@@ -75,6 +75,10 @@ var (
 		Name:  "human",
 		Usage: "\"Human-readable\" output",
 	}
+	NDJSONFlag = &cli.BoolFlag{
+		Name:  "ndjson",
+		Usage: "Output one JSON result per line as tests complete (streaming)",
+	}
 	StatDumpFlag = &cli.BoolFlag{
 		Name:  "statdump",
 		Usage: "displays stack and heap memory information",

cmd/evm/reporter.go

@@ -85,3 +85,9 @@ func report(ctx *cli.Context, results []testResult) {
 	out, _ := json.MarshalIndent(results, "", "  ")
 	fmt.Println(string(out))
 }
+
+// reportNDJSON prints one JSON object per result as it completes.
+func reportNDJSON(r testResult) {
+	out, _ := json.Marshal(r)
+	fmt.Println(string(out))
+}

cmd/evm/staterunner.go

@@ -56,6 +56,7 @@ var stateTestCommand = &cli.Command{
 		DumpFlag,
 		forkFlag,
 		HumanReadableFlag,
+		NDJSONFlag,
 		idxFlag,
 		RunFlag,
 		WorkersFlag,
@@ -76,7 +77,9 @@ func stateTestCmd(ctx *cli.Context) error {
 		if err != nil {
 			return err
 		}
-		report(ctx, results)
+		if !ctx.Bool(NDJSONFlag.Name) {
+			report(ctx, results)
+		}
 		return nil
 	}
 	// Otherwise, read filenames from stdin and execute back-to-back.
@@ -211,6 +214,9 @@ func runStateTest(ctx *cli.Context, fname string) ([]testResult, error) {
 					return
 				}
 			})
+			if ctx.Bool(NDJSONFlag.Name) {
+				reportNDJSON(*result)
+			}
 			results = append(results, *result)
 		}
 	}