cmd/evm: return json error if unmarshalling from stdin fails (ethereum#22871)

* cmd/evm: return json error if unmarshalling from stdin fails

* cmd/evm: make error capitalizations uniform (all lowercase starts)

* cmd/evm: capitalize error sent directly to stderror

Author: lightclient

cmd/evm/internal/t8ntool/transition.go

@@ -142,7 +142,9 @@ func Main(ctx *cli.Context) error {
 	// Figure out the prestate alloc
 	if allocStr == stdinSelector || envStr == stdinSelector || txStr == stdinSelector {
 		decoder := json.NewDecoder(os.Stdin)
-		decoder.Decode(inputData)
+		if err := decoder.Decode(inputData); err != nil {
+			return NewError(ErrorJson, fmt.Errorf("failed unmarshaling stdin: %v", err))
+		}
 	}
 	if allocStr != stdinSelector {
 		inFile, err := os.Open(allocStr)
@@ -152,7 +154,7 @@ func Main(ctx *cli.Context) error {
 		defer inFile.Close()
 		decoder := json.NewDecoder(inFile)
 		if err := decoder.Decode(&inputData.Alloc); err != nil {
-			return NewError(ErrorJson, fmt.Errorf("Failed unmarshaling alloc-file: %v", err))
+			return NewError(ErrorJson, fmt.Errorf("failed unmarshaling alloc-file: %v", err))
 		}
 	}
 	prestate.Pre = inputData.Alloc
@@ -167,7 +169,7 @@ func Main(ctx *cli.Context) error {
 		decoder := json.NewDecoder(inFile)
 		var env stEnv
 		if err := decoder.Decode(&env); err != nil {
-			return NewError(ErrorJson, fmt.Errorf("Failed unmarshaling env-file: %v", err))
+			return NewError(ErrorJson, fmt.Errorf("failed unmarshaling env-file: %v", err))
 		}
 		inputData.Env = &env
 	}
@@ -180,7 +182,7 @@ func Main(ctx *cli.Context) error {
 	// Construct the chainconfig
 	var chainConfig *params.ChainConfig
 	if cConf, extraEips, err := tests.GetChainConfig(ctx.String(ForknameFlag.Name)); err != nil {
-		return NewError(ErrorVMConfig, fmt.Errorf("Failed constructing chain configuration: %v", err))
+		return NewError(ErrorVMConfig, fmt.Errorf("failed constructing chain configuration: %v", err))
 	} else {
 		chainConfig = cConf
 		vmConfig.ExtraEips = extraEips
@@ -197,7 +199,7 @@ func Main(ctx *cli.Context) error {
 		defer inFile.Close()
 		decoder := json.NewDecoder(inFile)
 		if err := decoder.Decode(&txsWithKeys); err != nil {
-			return NewError(ErrorJson, fmt.Errorf("Failed unmarshaling txs-file: %v", err))
+			return NewError(ErrorJson, fmt.Errorf("failed unmarshaling txs-file: %v", err))
 		}
 	} else {
 		txsWithKeys = inputData.Txs
@@ -206,7 +208,7 @@ func Main(ctx *cli.Context) error {
 	signer := types.MakeSigner(chainConfig, big.NewInt(int64(prestate.Env.Number)))
 
 	if txs, err = signUnsignedTransactions(txsWithKeys, signer); err != nil {
-		return NewError(ErrorJson, fmt.Errorf("Failed signing transactions: %v", err))
+		return NewError(ErrorJson, fmt.Errorf("failed signing transactions: %v", err))
 	}
 
 	// Iterate over all the tests, run them and aggregate the results
@@ -277,7 +279,7 @@ func signUnsignedTransactions(txs []*txWithKey, signer types.Signer) (types.Tran
 			// This transaction needs to be signed
 			signed, err := types.SignTx(tx, signer, key)
 			if err != nil {
-				return nil, NewError(ErrorJson, fmt.Errorf("Tx %d: failed to sign tx: %v", i, err))
+				return nil, NewError(ErrorJson, fmt.Errorf("tx %d: failed to sign tx: %v", i, err))
 			}
 			signedTxs = append(signedTxs, signed)
 		} else {