eth/tracers: add diffMode to prestateTracer (#25422)

Backwards compatibility warning: The result will from now on omit empty fields instead
of including a zero value (e.g. no more `balance: '0x'`).

The prestateTracer will now take an option `diffMode: bool`. In this mode
the tracer will output the pre state and post data for the modified parts of state.
Read-only accesses will be completely omitted. Creations (be it account or slot)
will be signified by omission in the `pre` list and inclusion in `post`. Whereas
deletion (be it account or slot) will be signified by inclusion in `pre` and omission
in `post` list.
Signed-off-by: Delweng <delweng@gmail.com>

eth/tracers/internal/tracetest/calltrace_test.go

@@ -21,10 +21,8 @@ import (
 	"math/big"
 	"os"
 	"path/filepath"
-	"reflect"
 	"strings"
 	"testing"
-	"unicode"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
@@ -38,62 +36,8 @@ import (
 	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/tests"
-
-	// Force-load native and js packages, to trigger registration
-	_ "github.com/ethereum/go-ethereum/eth/tracers/js"
-	_ "github.com/ethereum/go-ethereum/eth/tracers/native"
 )
 
-// To generate a new callTracer test, copy paste the makeTest method below into
-// a Geth console and call it with a transaction hash you which to export.
-
-/*
-// makeTest generates a callTracer test by running a prestate reassembled and a
-// call trace run, assembling all the gathered information into a test case.
-var makeTest = function(tx, rewind) {
-  // Generate the genesis block from the block, transaction and prestate data
-  var block   = eth.getBlock(eth.getTransaction(tx).blockHash);
-  var genesis = eth.getBlock(block.parentHash);
-
-  delete genesis.gasUsed;
-  delete genesis.logsBloom;
-  delete genesis.parentHash;
-  delete genesis.receiptsRoot;
-  delete genesis.sha3Uncles;
-  delete genesis.size;
-  delete genesis.transactions;
-  delete genesis.transactionsRoot;
-  delete genesis.uncles;
-
-  genesis.gasLimit  = genesis.gasLimit.toString();
-  genesis.number    = genesis.number.toString();
-  genesis.timestamp = genesis.timestamp.toString();
-
-  genesis.alloc = debug.traceTransaction(tx, {tracer: "prestateTracer", rewind: rewind});
-  for (var key in genesis.alloc) {
-    genesis.alloc[key].nonce = genesis.alloc[key].nonce.toString();
-  }
-  genesis.config = admin.nodeInfo.protocols.eth.config;
-
-  // Generate the call trace and produce the test input
-  var result = debug.traceTransaction(tx, {tracer: "callTracer", rewind: rewind});
-  delete result.time;
-
-  console.log(JSON.stringify({
-    genesis: genesis,
-    context: {
-      number:     block.number.toString(),
-      difficulty: block.difficulty,
-      timestamp:  block.timestamp.toString(),
-      gasLimit:   block.gasLimit.toString(),
-      miner:      block.miner,
-    },
-    input:  eth.getRawTransaction(tx),
-    result: result,
-  }, null, 2));
-}
-*/
-
 type callContext struct {
 	Number     math.HexOrDecimal64   `json:"number"`
 	Difficulty *math.HexOrDecimal256 `json:"difficulty"`
@@ -204,7 +148,7 @@ func testCallTracer(tracerName string, dirPath string, t *testing.T) {
 				t.Fatalf("failed to unmarshal trace result: %v", err)
 			}
 
-			if !jsonEqual(ret, test.Result) {
+			if !jsonEqual(ret, test.Result, new(callTrace), new(callTrace)) {
 				// uncomment this for easier debugging
 				//have, _ := json.MarshalIndent(ret, "", " ")
 				//want, _ := json.MarshalIndent(test.Result, "", " ")
@@ -215,32 +159,6 @@ func testCallTracer(tracerName string, dirPath string, t *testing.T) {
 	}
 }
 
-// jsonEqual is similar to reflect.DeepEqual, but does a 'bounce' via json prior to
-// comparison
-func jsonEqual(x, y interface{}) bool {
-	xTrace := new(callTrace)
-	yTrace := new(callTrace)
-	if xj, err := json.Marshal(x); err == nil {
-		json.Unmarshal(xj, xTrace)
-	} else {
-		return false
-	}
-	if yj, err := json.Marshal(y); err == nil {
-		json.Unmarshal(yj, yTrace)
-	} else {
-		return false
-	}
-	return reflect.DeepEqual(xTrace, yTrace)
-}
-
-// camel converts a snake cased input string into a camel cased output.
-func camel(str string) string {
-	pieces := strings.Split(str, "_")
-	for i := 1; i < len(pieces); i++ {
-		pieces[i] = string(unicode.ToUpper(rune(pieces[i][0]))) + pieces[i][1:]
-	}
-	return strings.Join(pieces, "")
-}
 func BenchmarkTracers(b *testing.B) {
 	files, err := os.ReadDir(filepath.Join("testdata", "call_tracer"))
 	if err != nil {
@@ -386,7 +304,7 @@ func TestZeroValueToNotExitCall(t *testing.T) {
 	wantStr := `{"type":"CALL","from":"0x682a80a6f560eec50d54e63cbeda1c324c5f8d1b","to":"0x00000000000000000000000000000000deadbeef","value":"0x0","gas":"0x7148","gasUsed":"0x2d0","input":"0x","output":"0x","calls":[{"type":"CALL","from":"0x00000000000000000000000000000000deadbeef","to":"0x00000000000000000000000000000000000000ff","value":"0x0","gas":"0x6cbf","gasUsed":"0x0","input":"0x","output":"0x"}]}`
 	want := new(callTrace)
 	json.Unmarshal([]byte(wantStr), want)
-	if !jsonEqual(have, want) {
+	if !jsonEqual(have, want, new(callTrace), new(callTrace)) {
 		t.Error("have != want")
 	}
 }

eth/tracers/internal/tracetest/prestate_test.go

+// Copyright 2021 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package tracetest
+
+import (
+	"encoding/json"
+	"math/big"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core"
+	"github.com/ethereum/go-ethereum/core/rawdb"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/core/vm"
+	"github.com/ethereum/go-ethereum/eth/tracers"
+	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/ethereum/go-ethereum/tests"
+)
+
+// prestateTrace is the result of a prestateTrace run.
+type prestateTrace = map[common.Address]*account
+type account struct {
+	Balance string                      `json:"balance,omitempty"`
+	Nonce   uint64                      `json:"nonce,omitempty"`
+	Code    string                      `json:"code,omitempty"`
+	Storage map[common.Hash]common.Hash `json:"storage,omitempty"`
+}
+type prePostStateTrace struct {
+	Pre  prestateTrace `json:"pre"`
+	Post prestateTrace `json:"post"`
+}
+
+// prestateTraceTest defines a single test to check the stateDiff tracer against.
+type prestateTraceTest struct {
+	Genesis      *core.Genesis   `json:"genesis"`
+	Context      *callContext    `json:"context"`
+	Input        string          `json:"input"`
+	TracerConfig json.RawMessage `json:"tracerConfig"`
+	Result       interface{}     `json:"result"`
+}
+
+func TestPrestateTracer(t *testing.T) {
+	testPrestateDiffTracer("prestateTracer", "prestate_tracer", t, func() interface{} { return new(prestateTrace) })
+}
+
+func TestPrestateWithDiffModeTracer(t *testing.T) {
+	testPrestateDiffTracer("prestateTracer", "prestate_tracer_with_diff_mode", t, func() interface{} { return new(prePostStateTrace) })
+}
+
+func testPrestateDiffTracer(tracerName string, dirPath string, t *testing.T, typeBuilder func() interface{}) {
+	files, err := os.ReadDir(filepath.Join("testdata", dirPath))
+	if err != nil {
+		t.Fatalf("failed to retrieve tracer test suite: %v", err)
+	}
+	for _, file := range files {
+		if !strings.HasSuffix(file.Name(), ".json") {
+			continue
+		}
+		file := file // capture range variable
+		t.Run(camel(strings.TrimSuffix(file.Name(), ".json")), func(t *testing.T) {
+			t.Parallel()
+
+			var (
+				test = new(prestateTraceTest)
+				tx   = new(types.Transaction)
+			)
+			// Call tracer test found, read if from disk
+			if blob, err := os.ReadFile(filepath.Join("testdata", dirPath, file.Name())); err != nil {
+				t.Fatalf("failed to read testcase: %v", err)
+			} else if err := json.Unmarshal(blob, test); err != nil {
+				t.Fatalf("failed to parse testcase: %v", err)
+			}
+			if err := rlp.DecodeBytes(common.FromHex(test.Input), tx); err != nil {
+				t.Fatalf("failed to parse testcase input: %v", err)
+			}
+			// Configure a blockchain with the given prestate
+			var (
+				signer    = types.MakeSigner(test.Genesis.Config, new(big.Int).SetUint64(uint64(test.Context.Number)))
+				origin, _ = signer.Sender(tx)
+				txContext = vm.TxContext{
+					Origin:   origin,
+					GasPrice: tx.GasPrice(),
+				}
+				context = vm.BlockContext{
+					CanTransfer: core.CanTransfer,
+					Transfer:    core.Transfer,
+					Coinbase:    test.Context.Miner,
+					BlockNumber: new(big.Int).SetUint64(uint64(test.Context.Number)),
+					Time:        new(big.Int).SetUint64(uint64(test.Context.Time)),
+					Difficulty:  (*big.Int)(test.Context.Difficulty),
+					GasLimit:    uint64(test.Context.GasLimit),
+				}
+				_, statedb = tests.MakePreState(rawdb.NewMemoryDatabase(), test.Genesis.Alloc, false)
+			)
+			tracer, err := tracers.New(tracerName, new(tracers.Context), test.TracerConfig)
+			if err != nil {
+				t.Fatalf("failed to create call tracer: %v", err)
+			}
+			evm := vm.NewEVM(context, txContext, statedb, test.Genesis.Config, vm.Config{Debug: true, Tracer: tracer})
+			msg, err := tx.AsMessage(signer, nil)
+			if err != nil {
+				t.Fatalf("failed to prepare transaction for tracing: %v", err)
+			}
+			st := core.NewStateTransition(evm, msg, new(core.GasPool).AddGas(tx.Gas()))
+			if _, err = st.TransitionDb(); err != nil {
+				t.Fatalf("failed to execute transaction: %v", err)
+			}
+			// Retrieve the trace result and compare against the etalon
+			res, err := tracer.GetResult()
+			if err != nil {
+				t.Fatalf("failed to retrieve trace result: %v", err)
+			}
+			ret := typeBuilder()
+			if err := json.Unmarshal(res, ret); err != nil {
+				t.Fatalf("failed to unmarshal trace result: %v", err)
+			}
+
+			if !jsonEqual(ret, test.Result, typeBuilder(), typeBuilder()) {
+				// uncomment this for easier debugging
+				// have, _ := json.MarshalIndent(ret, "", " ")
+				// want, _ := json.MarshalIndent(test.Result, "", " ")
+				// t.Fatalf("trace mismatch: \nhave %+v\nwant %+v", string(have), string(want))
+				t.Fatalf("trace mismatch: \nhave %+v\nwant %+v", ret, test.Result)
+			}
+		})
+	}
+}

eth/tracers/internal/tracetest/testdata/prestate_tracer_with_diff_mode/create.json

+{
+  "genesis": {
+    "difficulty": "13756228101629",
+    "extraData": "0xd983010302844765746887676f312e342e328777696e646f7773",
+    "gasLimit": "3141592",
+    "hash": "0x58b7a87b6ba10b46b4e251d64ebc3d9822dd82218eaf24dff6796f6f1f687251",
+    "miner": "0xf8b483dba2c3b7176a3da549ad41a48bb3121069",
+    "mixHash": "0x5984b9a316116bd890e6e5f4c52d655184b0d7aa74821e1382d7760f9803c1dd",
+    "nonce": "0xea4bb4997242c681",
+    "number": "1061221",
+    "stateRoot": "0x5402c04d481414248d824c3b61e924e0c9307adbc9fbaae774a74cce30a4163d",
+    "timestamp": "1456458069",
+    "totalDifficulty": "7930751135586064334",
+    "alloc": {
+      "0x2a65aca4d5fc5b5c859090a6c34d164135398226": {
+        "balance": "0x9fb6b81e112638b886",
+        "nonce": "217865",
+        "code": "0x"
+      },
+      "0xf0c5cef39b17c213cfe090a46b8c7760ffb7928a": {
+        "balance": "0x15b6828e22bb12188",
+        "nonce": "747",
+        "code": "0x"
+      }
+    },
+    "config": {
+      "chainId": 1,
+      "homesteadBlock": 1150000,
+      "daoForkBlock": 1920000,
+      "daoForkSupport": true,
+      "eip150Block": 2463000,
+      "eip150Hash": "0x2086799aeebeae135c246c65021c82b4e15a2c451340993aacfd2751886514f0",
+      "eip155Block": 2675000,
+      "eip158Block": 2675000,
+      "byzantiumBlock": 4370000,
+      "constantinopleBlock": 7280000,
+      "petersburgBlock": 7280000,
+      "istanbulBlock": 9069000,
+      "muirGlacierBlock": 9200000,
+      "berlinBlock": 12244000,
+      "londonBlock": 12965000,
+      "arrowGlacierBlock": 13773000,
+      "grayGlacierBlock": 15050000,
+      "ethash": {}
+    }
+  },
+  "context": {
+    "number": "1061222",
+    "difficulty": "13749511193633",
+    "timestamp": "1456458097",
+    "gasLimit": "3141592",
+    "miner": "0x2a65aca4d5fc5b5c859090a6c34d164135398226"
+  },
+  "input": "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",
+  "tracerConfig": {
+    "diffMode": true
+  },
+  "result": {
+    "pre": {
+      "0x2a65aca4d5fc5b5c859090a6c34d164135398226": {
+        "balance": "0x9fb6b81e112638b886",
+        "nonce": 217865
+      },
+      "0xf0c5cef39b17c213cfe090a46b8c7760ffb7928a": {
+        "balance": "0x15b6828e22bb12188",
+        "nonce": 747
+      }
+    },
+    "post": {
+      "0x2a65aca4d5fc5b5c859090a6c34d164135398226": {
+        "balance": "0x9fb71abdd2621d8886"
+      },
+      "0x40f2f445da6c9047554683fb382fba6769717116": {
+        "code": "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",
+        "storage": {
+          "0x0000000000000000000000000000000000000000000000000000000000000000": "0x000000000000000000000000f0c5cef39b17c213cfe090a46b8c7760ffb7928a",
+          "0x0000000000000000000000000000000000000000000000000000000000000001": "0x00000000000000000000000000000000000000000000000000000000000001ee",
+          "0xb10e2d527612073b26eecdfd717e6a320cf44b4afac2b0732d9fcbe2b7fa0cf6": "0x7b225f6964223a225a473466784a7245323639384866623839222c22666f726d",
+          "0xb10e2d527612073b26eecdfd717e6a320cf44b4afac2b0732d9fcbe2b7fa0cf7": "0x5f736f75726365223a22434c54523031222c22636f6d6d69746d656e745f6461",
+          "0xb10e2d527612073b26eecdfd717e6a320cf44b4afac2b0732d9fcbe2b7fa0cf8": "0x7465223a22222c22626f72726f7765725f6e616d65223a22222c22626f72726f",
+          "0xb10e2d527612073b26eecdfd717e6a320cf44b4afac2b0732d9fcbe2b7fa0cf9": "0x7765725f616464726573735f6c696e6531223a22222c22626f72726f7765725f",
+          "0xb10e2d527612073b26eecdfd717e6a320cf44b4afac2b0732d9fcbe2b7fa0cfa": "0x616464726573735f6c696e6532223a22222c22626f72726f7765725f636f6e74",
+          "0xb10e2d527612073b26eecdfd717e6a320cf44b4afac2b0732d9fcbe2b7fa0cfb": "0x616374223a22222c22626f72726f7765725f7374617465223a22222c22626f72",
+          "0xb10e2d527612073b26eecdfd717e6a320cf44b4afac2b0732d9fcbe2b7fa0cfc": "0x726f7765725f74797065223a22222c2270726f70657274795f61646472657373",
+          "0xb10e2d527612073b26eecdfd717e6a320cf44b4afac2b0732d9fcbe2b7fa0cfd": "0x223a22222c226c6f616e5f616d6f756e745f7772697474656e223a22222c226c",
+          "0xb10e2d527612073b26eecdfd717e6a320cf44b4afac2b0732d9fcbe2b7fa0cfe": "0x6f616e5f616d6f756e74223a22222c224c54565f7772697474656e223a22222c",
+          "0xb10e2d527612073b26eecdfd717e6a320cf44b4afac2b0732d9fcbe2b7fa0cff": "0x224c5456223a22222c2244534352223a22222c2270726f70657274795f747970",
+          "0xb10e2d527612073b26eecdfd717e6a320cf44b4afac2b0732d9fcbe2b7fa0d00": "0x65223a22222c2270726f70657274795f6465736372697074696f6e223a22222c",
+          "0xb10e2d527612073b26eecdfd717e6a320cf44b4afac2b0732d9fcbe2b7fa0d01": "0x226c656e646572223a22222c2267756172616e746f7273223a22222c226c696d",
+          "0xb10e2d527612073b26eecdfd717e6a320cf44b4afac2b0732d9fcbe2b7fa0d02": "0x69746564223a22222c226361705f616d6f756e74223a22222c226361705f7065",
+          "0xb10e2d527612073b26eecdfd717e6a320cf44b4afac2b0732d9fcbe2b7fa0d03": "0x7263656e745f7772697474656e223a22222c226361705f70657263656e746167",
+          "0xb10e2d527612073b26eecdfd717e6a320cf44b4afac2b0732d9fcbe2b7fa0d04": "0x65223a22222c227465726d5f7772697474656e223a22222c227465726d223a22",
+          "0xb10e2d527612073b26eecdfd717e6a320cf44b4afac2b0732d9fcbe2b7fa0d05": "0x222c22657874656e64223a22227d000000000000000000000000000000000000"
+        }
+      },
+      "0xf0c5cef39b17c213cfe090a46b8c7760ffb7928a": {
+        "balance": "0x15b058920efcc5188",
+        "nonce": 748
+      }
+    }
+  }
+}

eth/tracers/internal/tracetest/testdata/prestate_tracer_with_diff_mode/create_suicide.json

+{
+  "genesis": {
+    "difficulty": "6217248151198",
+    "extraData": "0xd783010103844765746887676f312e342e32856c696e7578",
+    "gasLimit": "3141592",
+    "hash": "0xe8bff55fe3e61936ef321cf3afaeb1ba2f7234e1e89535fa8ae39963caebe9c3",
+    "miner": "0x52bc44d5378309ee2abf1539bf71de1b7d7be3b5",
+    "mixHash": "0x03da00d5a15a064e5ebddf53cd0aaeb9a8aff0f40c0fb031a74f463d11ec83b8",
+    "nonce": "0x6575fe08c4167044",
+    "number": "243825",
+    "stateRoot": "0x47182fe2e6e740b8a76f82fe5c527d6ad548f805274f21792cf4047235b24fbf",
+    "timestamp": "1442424328",
+    "totalDifficulty": "1035061827427752845",
+    "alloc": {
+      "0x082d4cdf07f386ffa9258f52a5c49db4ac321ec6": {
+        "balance": "0xc820f93200f4000",
+        "nonce": "0x5E",
+        "code": "0x"
+      },
+      "0x332b656504f4eabb44c8617a42af37461a34e9dc": {
+        "balance": "0x11faea4f35e5af80000",
+        "code": "0x",
+        "storage": {
+          "0x0000000000000000000000000000000000000000000000000000000000000000": "0x0000000000000000000000000000000000000000000000000000000000000000"
+        }
+      },
+      "0x52bc44d5378309ee2abf1539bf71de1b7d7be3b5": {
+        "balance": "0xbf681825be002ac452",
+        "nonce": "0x70FA",
+        "code": "0x"
+      },
+      "0x82effbaaaf28614e55b2ba440fb198e0e5789b0f": {
+        "balance": "0xb3d0ac5cb94df6f6b0",
+        "nonce": "0x1",
+        "code": "0x"
+      }
+    },
+    "config": {
+      "chainId": 1,
+      "homesteadBlock": 1150000,
+      "daoForkBlock": 1920000,
+      "daoForkSupport": true,
+      "eip150Block": 2463000,
+      "eip150Hash": "0x2086799aeebeae135c246c65021c82b4e15a2c451340993aacfd2751886514f0",
+      "eip155Block": 2675000,
+      "eip158Block": 2675000,
+      "byzantiumBlock": 4370000,
+      "constantinopleBlock": 7280000,
+      "petersburgBlock": 7280000,
+      "istanbulBlock": 9069000,
+      "muirGlacierBlock": 9200000,
+      "berlinBlock": 12244000,
+      "londonBlock": 12965000,
+      "arrowGlacierBlock": 13773000,
+      "grayGlacierBlock": 15050000,
+      "ethash": {}
+    }
+  },
+  "context": {
+    "number": "243826",
+    "difficulty": "6214212385501",
+    "timestamp": "1442424353",
+    "gasLimit": "3141592",
+    "miner": "0x52bc44d5378309ee2abf1539bf71de1b7d7be3b5"
+  },
+  "input": "0xf8e85e850ba43b7400830f42408080b89660606040527382effbaaaf28614e55b2ba440fb198e0e5789b0f600060006101000a81548173ffffffffffffffffffffffffffffffffffffffff021916908302179055505b600060009054906101000a900473ffffffffffffffffffffffffffffffffffffffff1673ffffffffffffffffffffffffffffffffffffffff16ff5b600a80608c6000396000f30060606040526008565b001ca0340b21661e5bb85a46319a15f33a362e5c0f02faa7cdbf9c5808b2134da968eaa0226e6788f8c20e211d436ab7f6298ef32fa4c23a509eeeaac0880d115c17bc3f",
+  "tracerConfig": {
+    "diffMode": true
+  },
+  "result": {
+    "pre": {
+      "0x082d4cdf07f386ffa9258f52a5c49db4ac321ec6": {
+        "balance": "0xc820f93200f4000",
+        "nonce": 94
+      },
+      "0x332b656504f4eabb44c8617a42af37461a34e9dc": {
+        "balance": "0x11faea4f35e5af80000",
+        "storage": {
+          "0x0000000000000000000000000000000000000000000000000000000000000000": "0x0000000000000000000000000000000000000000000000000000000000000000"
+        }
+      },
+      "0x52bc44d5378309ee2abf1539bf71de1b7d7be3b5": {
+        "balance": "0xbf681825be002ac452",
+        "nonce": 28922
+      },
+      "0x82effbaaaf28614e55b2ba440fb198e0e5789b0f": {
+        "balance": "0xb3d0ac5cb94df6f6b0",
+        "nonce": 1
+      }
+    },
+    "post": {
+      "0x082d4cdf07f386ffa9258f52a5c49db4ac321ec6": {
+        "balance": "0xc7d4d88af8b4c00",
+        "nonce": 95
+      },
+      "0x52bc44d5378309ee2abf1539bf71de1b7d7be3b5": {
+        "balance": "0xbf681ce7c870aeb852"
+      },
+      "0x82effbaaaf28614e55b2ba440fb198e0e5789b0f": {
+        "balance": "0x1d37f515017a8eef6b0"
+      }
+    }
+  }
+}

eth/tracers/internal/tracetest/util.go

+package tracetest
+
+import (
+	"encoding/json"
+	"reflect"
+	"strings"
+	"unicode"
+
+	// Force-load native and js pacakges, to trigger registration
+	_ "github.com/ethereum/go-ethereum/eth/tracers/js"
+	_ "github.com/ethereum/go-ethereum/eth/tracers/native"
+)
+
+// To generate a new callTracer test, copy paste the makeTest method below into
+// a Geth console and call it with a transaction hash you which to export.
+
+/*
+// makeTest generates a callTracer test by running a prestate reassembled and a
+// call trace run, assembling all the gathered information into a test case.
+var makeTest = function(tx, rewind) {
+  // Generate the genesis block from the block, transaction and prestate data
+  var block   = eth.getBlock(eth.getTransaction(tx).blockHash);
+  var genesis = eth.getBlock(block.parentHash);
+
+  delete genesis.gasUsed;
+  delete genesis.logsBloom;
+  delete genesis.parentHash;
+  delete genesis.receiptsRoot;
+  delete genesis.sha3Uncles;
+  delete genesis.size;
+  delete genesis.transactions;
+  delete genesis.transactionsRoot;
+  delete genesis.uncles;
+
+  genesis.gasLimit  = genesis.gasLimit.toString();
+  genesis.number    = genesis.number.toString();
+  genesis.timestamp = genesis.timestamp.toString();
+
+  genesis.alloc = debug.traceTransaction(tx, {tracer: "prestateTracer", rewind: rewind});
+  for (var key in genesis.alloc) {
+    var nonce = genesis.alloc[key].nonce;
+    if (nonce) {
+      genesis.alloc[key].nonce = nonce.toString();
+    }
+  }
+  genesis.config = admin.nodeInfo.protocols.eth.config;
+
+  // Generate the call trace and produce the test input
+  var result = debug.traceTransaction(tx, {tracer: "callTracer", rewind: rewind});
+  delete result.time;
+
+  console.log(JSON.stringify({
+    genesis: genesis,
+    context: {
+      number:     block.number.toString(),
+      difficulty: block.difficulty,
+      timestamp:  block.timestamp.toString(),
+      gasLimit:   block.gasLimit.toString(),
+      miner:      block.miner,
+    },
+    input:  eth.getRawTransaction(tx),
+    result: result,
+  }, null, 2));
+}
+*/
+
+// jsonEqual is similar to reflect.DeepEqual, but does a 'bounce' via json prior to
+// comparison
+func jsonEqual(xi, yi, xt, yt interface{}) bool {
+	if xj, err := json.Marshal(xi); err == nil {
+		json.Unmarshal(xj, xt)
+	} else {
+		return false
+	}
+	if yj, err := json.Marshal(yi); err == nil {
+		json.Unmarshal(yj, yt)
+	} else {
+		return false
+	}
+	return reflect.DeepEqual(xt, yt)
+}
+
+// camel converts a snake cased input string into a camel cased output.
+func camel(str string) string {
+	pieces := strings.Split(str, "_")
+	for i := 1; i < len(pieces); i++ {
+		pieces[i] = string(unicode.ToUpper(rune(pieces[i][0]))) + pieces[i][1:]
+	}
+	return strings.Join(pieces, "")
+}

eth/tracers/native/gen_account_json.go

@@ -15,10 +15,10 @@ var _ = (*accountMarshaling)(nil)
 // MarshalJSON marshals as JSON.
 func (a account) MarshalJSON() ([]byte, error) {
 	type account struct {
-		Balance *hexutil.Big                `json:"balance"`
-		Nonce   uint64                      `json:"nonce"`
-		Code    hexutil.Bytes               `json:"code"`
-		Storage map[common.Hash]common.Hash `json:"storage"`
+		Balance *hexutil.Big                `json:"balance,omitempty"`
+		Nonce   uint64                      `json:"nonce,omitempty"`
+		Code    hexutil.Bytes               `json:"code,omitempty"`
+		Storage map[common.Hash]common.Hash `json:"storage,omitempty"`
 	}
 	var enc account
 	enc.Balance = (*hexutil.Big)(a.Balance)

eth/tracers/native/prestate.go

@@ -17,6 +17,7 @@
 package native
 
 import (
+	"bytes"
 	"encoding/json"
 	"math/big"
 	"sync/atomic"
@@ -35,12 +36,13 @@ func init() {
 	register("prestateTracer", newPrestateTracer)
 }
 
-type prestate = map[common.Address]*account
+type state = map[common.Address]*account
+
 type account struct {
-	Balance *big.Int                    `json:"balance"`
-	Nonce   uint64                      `json:"nonce"`
-	Code    []byte                      `json:"code"`
-	Storage map[common.Hash]common.Hash `json:"storage"`
+	Balance *big.Int                    `json:"balance,omitempty"`
+	Nonce   uint64                      `json:"nonce,omitempty"`
+	Code    []byte                      `json:"code,omitempty"`
+	Storage map[common.Hash]common.Hash `json:"storage,omitempty"`
 }
 
 type accountMarshaling struct {
@@ -50,18 +52,38 @@ type accountMarshaling struct {
 
 type prestateTracer struct {
 	env       *vm.EVM
-	prestate  prestate
+	pre       state
+	post      state
 	create    bool
 	to        common.Address
 	gasLimit  uint64 // Amount of gas bought for the whole tx
+	config    prestateTracerConfig
 	interrupt uint32 // Atomic flag to signal execution interruption
 	reason    error  // Textual reason for the interruption
+	created   map[common.Address]bool
+	deleted   map[common.Address]bool
+}
+
+type prestateTracerConfig struct {
+	DiffMode bool `json:"diffMode"` // If true, this tracer will return all diff states
 }
 
-func newPrestateTracer(ctx *tracers.Context, _ json.RawMessage) (tracers.Tracer, error) {
+func newPrestateTracer(ctx *tracers.Context, cfg json.RawMessage) (tracers.Tracer, error) {
 	// First callframe contains tx context info
 	// and is populated on start and end.
-	return &prestateTracer{prestate: prestate{}}, nil
+	var config prestateTracerConfig
+	if cfg != nil {
+		if err := json.Unmarshal(cfg, &config); err != nil {
+			return nil, err
+		}
+	}
+	return &prestateTracer{
+		pre:     state{},
+		post:    state{},
+		config:  config,
+		created: make(map[common.Address]bool),
+		deleted: make(map[common.Address]bool),
+	}, nil
 }
 
 // CaptureStart implements the EVMLogger interface to initialize the tracing operation.
@@ -72,26 +94,31 @@ func (t *prestateTracer) CaptureStart(env *vm.EVM, from common.Address, to commo
 
 	t.lookupAccount(from)
 	t.lookupAccount(to)
+	t.lookupAccount(env.Context.Coinbase)
 
 	// The recipient balance includes the value transferred.
-	toBal := new(big.Int).Sub(t.prestate[to].Balance, value)
-	t.prestate[to].Balance = toBal
+	toBal := new(big.Int).Sub(t.pre[to].Balance, value)
+	t.pre[to].Balance = toBal
 
 	// The sender balance is after reducing: value and gasLimit.
 	// We need to re-add them to get the pre-tx balance.
-	fromBal := new(big.Int).Set(t.prestate[from].Balance)
+	fromBal := new(big.Int).Set(t.pre[from].Balance)
 	gasPrice := env.TxContext.GasPrice
 	consumedGas := new(big.Int).Mul(gasPrice, new(big.Int).SetUint64(t.gasLimit))
 	fromBal.Add(fromBal, new(big.Int).Add(value, consumedGas))
-	t.prestate[from].Balance = fromBal
-	t.prestate[from].Nonce--
+	t.pre[from].Balance = fromBal
+	t.pre[from].Nonce--
+
+	if create && t.config.DiffMode {
+		t.created[to] = true
+	}
 }
 
 // CaptureEnd is called after the call finishes to finalize the tracing.
 func (t *prestateTracer) CaptureEnd(output []byte, gasUsed uint64, _ time.Duration, err error) {
-	if t.create {
+	if t.create && !t.config.DiffMode {
 		// Exclude created contract.
-		delete(t.prestate, t.to)
+		delete(t.pre, t.to)
 	}
 }
 
@@ -100,27 +127,34 @@ func (t *prestateTracer) CaptureState(pc uint64, op vm.OpCode, gas, cost uint64,
 	stack := scope.Stack
 	stackData := stack.Data()
 	stackLen := len(stackData)
+	caller := scope.Contract.Address()
 	switch {
 	case stackLen >= 1 && (op == vm.SLOAD || op == vm.SSTORE):
 		slot := common.Hash(stackData[stackLen-1].Bytes32())
-		t.lookupStorage(scope.Contract.Address(), slot)
+		t.lookupStorage(caller, slot)
 	case stackLen >= 1 && (op == vm.EXTCODECOPY || op == vm.EXTCODEHASH || op == vm.EXTCODESIZE || op == vm.BALANCE || op == vm.SELFDESTRUCT):
 		addr := common.Address(stackData[stackLen-1].Bytes20())
 		t.lookupAccount(addr)
+		if op == vm.SELFDESTRUCT {
+			t.deleted[caller] = true
+		}
 	case stackLen >= 5 && (op == vm.DELEGATECALL || op == vm.CALL || op == vm.STATICCALL || op == vm.CALLCODE):
 		addr := common.Address(stackData[stackLen-2].Bytes20())
 		t.lookupAccount(addr)
 	case op == vm.CREATE:
-		addr := scope.Contract.Address()
-		nonce := t.env.StateDB.GetNonce(addr)
-		t.lookupAccount(crypto.CreateAddress(addr, nonce))
+		nonce := t.env.StateDB.GetNonce(caller)
+		addr := crypto.CreateAddress(caller, nonce)
+		t.lookupAccount(addr)
+		t.created[addr] = true
 	case stackLen >= 4 && op == vm.CREATE2:
 		offset := stackData[stackLen-2]
 		size := stackData[stackLen-3]
 		init := scope.Memory.GetCopy(int64(offset.Uint64()), int64(size.Uint64()))
 		inithash := crypto.Keccak256(init)
 		salt := stackData[stackLen-4]
-		t.lookupAccount(crypto.CreateAddress2(scope.Contract.Address(), salt.Bytes32(), inithash))
+		addr := crypto.CreateAddress2(caller, salt.Bytes32(), inithash)
+		t.lookupAccount(addr)
+		t.created[addr] = true
 	}
 }
 
@@ -141,12 +175,79 @@ func (t *prestateTracer) CaptureTxStart(gasLimit uint64) {
 	t.gasLimit = gasLimit
 }
 
-func (t *prestateTracer) CaptureTxEnd(restGas uint64) {}
+func (t *prestateTracer) CaptureTxEnd(restGas uint64) {
+	if !t.config.DiffMode {
+		return
+	}
+
+	for addr, state := range t.pre {
+		// the deleted account's state is pruned
+		if _, ok := t.deleted[addr]; ok {
+			continue
+		}
+		modified := false
+		postAccount := &account{Storage: make(map[common.Hash]common.Hash)}
+		newBalance := t.env.StateDB.GetBalance(addr)
+		newNonce := t.env.StateDB.GetNonce(addr)
+		newCode := t.env.StateDB.GetCode(addr)
+
+		if newBalance.Cmp(t.pre[addr].Balance) != 0 {
+			modified = true
+			postAccount.Balance = newBalance
+		}
+		if newNonce != t.pre[addr].Nonce {
+			modified = true
+			postAccount.Nonce = newNonce
+		}
+		if !bytes.Equal(newCode, t.pre[addr].Code) {
+			modified = true
+			postAccount.Code = newCode
+		}
+
+		for key, val := range state.Storage {
+			// don't include the empty slot
+			if val == (common.Hash{}) {
+				delete(t.pre[addr].Storage, key)
+			}
+
+			newVal := t.env.StateDB.GetState(addr, key)
+			if val != newVal {
+				modified = true
+				if newVal != (common.Hash{}) {
+					postAccount.Storage[key] = newVal
+				}
+			}
+		}
+
+		if modified {
+			t.post[addr] = postAccount
+		} else {
+			// if state is not modified, then no need to include into the pre state
+			delete(t.pre, addr)
+		}
+	}
+	// the new created contracts' prestate were empty, so delete them
+	for a := range t.created {
+		// the created contract maybe exists in statedb before the creating tx
+		if s := t.pre[a]; s.Balance.Cmp(big.NewInt(0)) == 0 && len(s.Storage) == 0 && len(s.Code) == 0 {
+			delete(t.pre, a)
+		}
+	}
+}
 
 // GetResult returns the json-encoded nested list of call traces, and any
 // error arising from the encoding or forceful termination (via `Stop`).
 func (t *prestateTracer) GetResult() (json.RawMessage, error) {
-	res, err := json.Marshal(t.prestate)
+	var res []byte
+	var err error
+	if t.config.DiffMode {
+		res, err = json.Marshal(struct {
+			Pre  state `json:"pre"`
+			Post state `json:"post"`
+		}{t.pre, t.post})
+	} else {
+		res, err = json.Marshal(t.pre)
+	}
 	if err != nil {
 		return nil, err
 	}
@@ -162,10 +263,11 @@ func (t *prestateTracer) Stop(err error) {
 // lookupAccount fetches details of an account and adds it to the prestate
 // if it doesn't exist there.
 func (t *prestateTracer) lookupAccount(addr common.Address) {
-	if _, ok := t.prestate[addr]; ok {
+	if _, ok := t.pre[addr]; ok {
 		return
 	}
-	t.prestate[addr] = &account{
+
+	t.pre[addr] = &account{
 		Balance: t.env.StateDB.GetBalance(addr),
 		Nonce:   t.env.StateDB.GetNonce(addr),
 		Code:    t.env.StateDB.GetCode(addr),
@@ -177,8 +279,8 @@ func (t *prestateTracer) lookupAccount(addr common.Address) {
 // it to the prestate of the given contract. It assumes `lookupAccount`
 // has been performed on the contract before.
 func (t *prestateTracer) lookupStorage(addr common.Address, key common.Hash) {
-	if _, ok := t.prestate[addr].Storage[key]; ok {
+	if _, ok := t.pre[addr].Storage[key]; ok {
 		return
 	}
-	t.prestate[addr].Storage[key] = t.env.StateDB.GetState(addr, key)
+	t.pre[addr].Storage[key] = t.env.StateDB.GetState(addr, key)
 }