Add broadcast API to Go forge scripts

Adds a hooks-based API to collect transactions broadcasted via `vm.broadcast(*)` in the Go-based Forge scripts. Users pass an `OnBroadcast` hook to the host, which will be called with a `Broadcast` struct with the following fields whenever a transaction needs to be emitted:

```go
type Broadcast struct {
	From     common.Address
	To       common.Address
	Calldata []byte
	Value    *big.Int
}
```

This API lets us layer on custom transaction management in the future which will be helpful for `op-deployer`.

As part of this PR, I changed the internal `callStack` data structure to contain pointers to `CallFrame`s rather than passing by value. I discovered a bug where the pranked sender was not being cleared in subsequent calls due to an ineffectual assignment error. I took a look at the implementation and there are many places where assignments to call frames within the stack happen after converting the value to a reference, so converting the stack to store pointers in the first place both simplified the code and eliminated a class of errors in the future. I updated the public API methods to return copies of the internal structs to prevent accidental mutation.

op-chain-ops/script/prank.go

@@ -69,7 +69,7 @@ func (h *Host) Prank(msgSender *common.Address, txOrigin *common.Address, repeat
 		h.log.Warn("no call stack")
 		return nil // cannot prank while not in a call.
 	}
-	cf := &h.callStack[len(h.callStack)-1]
+	cf := h.callStack[len(h.callStack)-1]
 	if cf.Prank != nil {
 		if cf.Prank.Broadcast && !broadcast {
 			return errors.New("you have an active broadcast; broadcasting and pranks are not compatible")
@@ -98,7 +98,7 @@ func (h *Host) StopPrank(broadcast bool) error {
 	if len(h.callStack) == 0 {
 		return nil
 	}
-	cf := &h.callStack[len(h.callStack)-1]
+	cf := h.callStack[len(h.callStack)-1]
 	if cf.Prank == nil {
 		if broadcast {
 			return errors.New("no broadcast in progress to stop")
@@ -127,7 +127,7 @@ func (h *Host) CallerMode() CallerMode {
 	if len(h.callStack) == 0 {
 		return CallerModeNone
 	}
-	cf := &h.callStack[len(h.callStack)-1]
+	cf := h.callStack[len(h.callStack)-1]
 	if cf.Prank != nil {
 		if cf.Prank.Broadcast {
 			if cf.Prank.Repeat {

op-chain-ops/script/script.go

@@ -3,6 +3,7 @@ package script
 import (
 	"bytes"
 	"encoding/binary"
+	"encoding/hex"
 	"encoding/json"
 	"fmt"
 	"math/big"
@@ -54,6 +55,33 @@ type CallFrame struct {
 	Prank *Prank
 }
 
+type Broadcast struct {
+	From     common.Address
+	To       common.Address
+	Calldata []byte
+	Value    *big.Int
+}
+
+var zero = big.NewInt(0)
+
+func NewBroadcastFromCtx(ctx *vm.ScopeContext) Broadcast {
+	value := ctx.CallValue().ToBig()
+	if value.Cmp(zero) == 0 {
+		value = nil
+	}
+
+	callInput := ctx.CallInput()
+	calldata := make([]byte, len(callInput))
+	copy(calldata, callInput)
+
+	return Broadcast{
+		From:     ctx.Caller(),
+		To:       ctx.Address(),
+		Calldata: calldata,
+		Value:    value,
+	}
+}
+
 // Host is an EVM executor that runs Forge scripts.
 type Host struct {
 	log      log.Logger
@@ -69,7 +97,7 @@ type Host struct {
 
 	precompiles map[common.Address]vm.PrecompiledContract
 
-	callStack []CallFrame
+	callStack []*CallFrame
 
 	// serializerStates are in-progress JSON payloads by name,
 	// for the serializeX family of cheat codes, see:
@@ -86,12 +114,26 @@ type Host struct {
 	srcMaps map[common.Address]*srcmap.SourceMap
 
 	onLabel []func(name string, addr common.Address)
+
+	hooks *Hooks
+}
+
+type Hooks struct {
+	OnBroadcast func(broadcast Broadcast)
+}
+
+var defaultHooks = &Hooks{
+	OnBroadcast: func(broadcast Broadcast) {},
+}
+
+func NewHost(logger log.Logger, fs *foundry.ArtifactsFS, srcFS *foundry.SourceMapFS, executionContext Context) *Host {
+	return NewHostWithHooks(logger, fs, srcFS, executionContext, nil)
 }
 
-// NewHost creates a Host that can load contracts from the given Artifacts FS,
+// NewHostWithHooks creates a Host that can load contracts from the given Artifacts FS,
 // and with an EVM initialized to the given executionContext.
 // Optionally src-map loading may be enabled, by providing a non-nil srcFS to read sources from.
-func NewHost(logger log.Logger, fs *foundry.ArtifactsFS, srcFS *foundry.SourceMapFS, executionContext Context) *Host {
+func NewHostWithHooks(logger log.Logger, fs *foundry.ArtifactsFS, srcFS *foundry.SourceMapFS, executionContext Context, hooks *Hooks) *Host {
 	h := &Host{
 		log:              logger,
 		af:               fs,
@@ -101,6 +143,11 @@ func NewHost(logger log.Logger, fs *foundry.ArtifactsFS, srcFS *foundry.SourceMa
 		precompiles:      make(map[common.Address]vm.PrecompiledContract),
 		srcFS:            srcFS,
 		srcMaps:          make(map[common.Address]*srcmap.SourceMap),
+		hooks:            defaultHooks,
+	}
+
+	if hooks != nil {
+		h.hooks = hooks
 	}
 
 	// Init a default chain config, with all the mainnet L1 forks activated
@@ -361,6 +408,19 @@ func (h *Host) unwindCallstack(depth int) {
 		if len(h.callStack) > 1 {
 			parentCallFrame := h.callStack[len(h.callStack)-2]
 			if parentCallFrame.Prank != nil {
+				if parentCallFrame.Prank.Broadcast {
+					currentFrame := h.callStack[len(h.callStack)-1]
+					bcast := NewBroadcastFromCtx(currentFrame.Ctx)
+					h.hooks.OnBroadcast(bcast)
+					h.log.Debug(
+						"called broadcast hook",
+						"from", bcast.From,
+						"to", bcast.To,
+						"calldata", hex.EncodeToString(bcast.Calldata),
+						"value", bcast.Value,
+					)
+				}
+
 				// While going back to the parent, restore the tx.origin.
 				// It will later be re-applied on sub-calls if the prank persists (if Repeat == true).
 				if parentCallFrame.Prank.Origin != nil {
@@ -372,7 +432,7 @@ func (h *Host) unwindCallstack(depth int) {
 			}
 		}
 		// Now pop the call-frame
-		h.callStack[len(h.callStack)-1] = CallFrame{} // don't hold on to the underlying call-frame resources
+		h.callStack[len(h.callStack)-1] = nil // don't hold on to the underlying call-frame resources
 		h.callStack = h.callStack[:len(h.callStack)-1]
 	}
 }
@@ -384,7 +444,7 @@ func (h *Host) onOpcode(pc uint64, op byte, gas, cost uint64, scope tracing.OpCo
 	// Check if we are entering a new depth, add it to the call-stack if so.
 	// We do this here, instead of onEnter, to capture an initialized scope.
 	if len(h.callStack) == 0 || h.callStack[len(h.callStack)-1].Depth < depth {
-		h.callStack = append(h.callStack, CallFrame{
+		h.callStack = append(h.callStack, &CallFrame{
 			Depth:  depth,
 			LastOp: vm.OpCode(op),
 			LastPC: pc,
@@ -395,7 +455,7 @@ func (h *Host) onOpcode(pc uint64, op byte, gas, cost uint64, scope tracing.OpCo
 	if len(h.callStack) == 0 || h.callStack[len(h.callStack)-1].Ctx != scopeCtx {
 		panic("scope context changed without call-frame pop/push")
 	}
-	cf := &h.callStack[len(h.callStack)-1]
+	cf := h.callStack[len(h.callStack)-1]
 	if vm.OpCode(op) == vm.JUMPDEST { // remember the last PC before successful jump
 		cf.LastJumps = append(cf.LastJumps, cf.LastPC)
 		if len(cf.LastJumps) > jumpHistory {
@@ -429,7 +489,7 @@ func (h *Host) CurrentCall() CallFrame {
 	if len(h.callStack) == 0 {
 		return CallFrame{}
 	}
-	return h.callStack[len(h.callStack)-1]
+	return *h.callStack[len(h.callStack)-1]
 }
 
 // MsgSender returns the msg.sender of the current active EVM call-frame,

op-chain-ops/script/script_test.go

@@ -1,6 +1,10 @@
 package script
 
 import (
+	"fmt"
+	"github.com/ethereum/go-ethereum/accounts/abi"
+	"github.com/ethereum/go-ethereum/common"
+	"strings"
 	"testing"
 
 	"github.com/holiman/uint256"
@@ -35,3 +39,58 @@ func TestScript(t *testing.T) {
 	// and a second time, to see if we can revisit the host state.
 	require.NoError(t, h.cheatcodes.Precompile.DumpState("noop"))
 }
+
+func TestScriptBroadcast(t *testing.T) {
+	logger := testlog.Logger(t, log.LevelDebug)
+	af := foundry.OpenArtifactsDir("./testdata/test-artifacts")
+
+	mustEncodeCalldata := func(method, input string) []byte {
+		packer, err := abi.JSON(strings.NewReader(fmt.Sprintf(`[{"type":"function","name":"%s","inputs":[{"type":"string","name":"input"}]}]`, method)))
+		require.NoError(t, err)
+
+		data, err := packer.Pack(method, input)
+		require.NoError(t, err)
+		return data
+	}
+
+	senderAddr := common.HexToAddress("0x5b73C5498c1E3b4dbA84de0F1833c4a029d90519")
+	expBroadcasts := []Broadcast{
+		{
+			From:     senderAddr,
+			To:       senderAddr,
+			Calldata: mustEncodeCalldata("call1", "single_call1"),
+		},
+		{
+			From:     senderAddr,
+			To:       senderAddr,
+			Calldata: mustEncodeCalldata("call1", "startstop_call1"),
+		},
+		{
+			From:     senderAddr,
+			To:       senderAddr,
+			Calldata: mustEncodeCalldata("call2", "startstop_call2"),
+		},
+		{
+			From:     senderAddr,
+			To:       senderAddr,
+			Calldata: mustEncodeCalldata("nested1", "nested"),
+		},
+	}
+
+	scriptContext := DefaultContext
+	var broadcasts []Broadcast
+	h := NewHostWithHooks(logger, af, nil, scriptContext, &Hooks{
+		OnBroadcast: func(broadcast Broadcast) {
+			broadcasts = append(broadcasts, broadcast)
+		},
+	})
+	addr, err := h.LoadContract("ScriptExample.s.sol", "ScriptExample")
+	require.NoError(t, err)
+
+	require.NoError(t, h.EnableCheats())
+
+	input := bytes4("runBroadcast()")
+	returnData, _, err := h.Call(scriptContext.Sender, addr, input[:], DefaultFoundryGasLimit, uint256.NewInt(0))
+	require.NoError(t, err, "call failed: %x", string(returnData))
+	require.EqualValues(t, expBroadcasts, broadcasts)
+}

op-chain-ops/script/testdata/scripts/ScriptExample.s.sol

@@ -8,6 +8,9 @@ interface Vm {
     function parseJsonKeys(string calldata json, string calldata key) external pure returns (string[] memory keys);
     function startPrank(address msgSender) external;
     function stopPrank() external;
+    function broadcast() external;
+    function startBroadcast() external;
+    function stopBroadcast() external;
 }
 
 // console is a minimal version of the console2 lib.
@@ -90,9 +93,45 @@ contract ScriptExample {
         console.log("done!");
     }
 
+    /// @notice example function, to test vm.broadcast with.
+    function runBroadcast() public {
+        console.log("testing single");
+        vm.broadcast();
+        this.call1("single_call1");
+        this.call2("single_call2");
+
+        console.log("testing start/stop");
+        vm.startBroadcast();
+        this.call1("startstop_call1");
+        this.call2("startstop_call2");
+        vm.stopBroadcast();
+        this.call1("startstop_call3");
+
+        console.log("testing nested");
+        vm.startBroadcast();
+        this.nested1("nested");
+        vm.stopBroadcast();
+    }
+
     /// @notice example external function, to force a CALL, and test vm.startPrank with.
     function hello(string calldata _v) external view {
         console.log(_v);
         console.log("hello msg.sender", address(msg.sender));
     }
+
+    function call1(string calldata _v) external pure {
+        console.log(_v);
+    }
+
+    function call2(string calldata _v) external pure {
+        console.log(_v);
+    }
+
+    function nested1(string calldata _v) external view {
+        this.nested2(_v);
+    }
+
+    function nested2(string calldata _v) external pure {
+        console.log(_v);
+    }
 }