evm: use stack of contexts to implement snapshot revert (#399)

* use stack of contexts to implement snapshot revert

Closes #338

add exception revert test case

verify partial revert

mutate state after the reverted subcall

polish

update comments

name the module after the type name

remove the unnecessary Snapshot in outer layer

and add snapshot unit test

assert context stack is clean after tx processing

cleanups

fix context revert

fix comments

update comments

it's ok to commit in failed case too

Update x/evm/keeper/context_stack.go

Co-authored-by: Federico Kunze Küllmer <31522760+fedekunze@users.noreply.github.com>

Update x/evm/keeper/context_stack.go

Co-authored-by: Federico Kunze Küllmer <31522760+fedekunze@users.noreply.github.com>

Update x/evm/keeper/context_stack.go

Co-authored-by: Federico Kunze Küllmer <31522760+fedekunze@users.noreply.github.com>

update comment and error message

add comment to cacheContext

k -> cs

Update x/evm/keeper/context_stack.go

Co-authored-by: Federico Kunze Küllmer <31522760+fedekunze@users.noreply.github.com>

evm can handle state revert

renames and unit tests

* use table driven tests

* keep all the cosmos events

* changelog

* check for if commit function is nil

* fix changelog

* Update x/evm/keeper/context_stack.go

Co-authored-by: Federico Kunze Küllmer <31522760+fedekunze@users.noreply.github.com>

CHANGELOG.md

@@ -49,6 +49,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (evm) [tharsis#342](https://github.com/tharsis/ethermint/issues/342) Don't clear balance when resetting the account.
 * (evm) [tharsis#334](https://github.com/tharsis/ethermint/pull/334) Log index changed to the index in block rather than
   tx.
+* (evm) [tharsis#399](https://github.com/tharsis/ethermint/pull/399) Exception in sub-message call reverts the call if it's not propagated.
 
 ### API Breaking
 

tests/solidity/suites/exception/contracts/TestRevert.sol

@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: MIT
+pragma solidity >=0.8.0;
+
+contract State {
+    uint256 a = 0;
+    function set(uint256 input) public { 
+        a = input; 
+        require(a < 10);
+    }
+    function force_set(uint256 input) public { 
+        a = input; 
+    }
+    function query() public view returns(uint256) {
+        return a;
+    }
+}
+
+contract TestRevert {
+    State state;
+    uint256 b = 0;
+    uint256 c = 0;
+    constructor() {
+        state = new State();
+    }
+    function try_set(uint256 input) public {
+        b = input;
+        try state.set(input) {
+        } catch (bytes memory) {
+        }
+        c = input;
+    }
+    function set(uint256 input) public {
+        state.force_set(input);
+    }
+    function query_a() public view returns(uint256) {
+        return state.query();
+    }
+    function query_b() public view returns(uint256) {
+        return b;
+    }
+    function query_c() public view returns(uint256) {
+        return c;
+    }
+}

tests/solidity/suites/exception/contracts/test/Migrations.sol

@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: MIT
+pragma solidity >=0.8.0;
+
+contract Migrations {
+  address public owner = msg.sender;
+  uint public last_completed_migration;
+
+  modifier restricted() {
+    require(
+      msg.sender == owner,
+      "This function is restricted to the contract's owner"
+    );
+    _;
+  }
+
+  function setCompleted(uint completed) public restricted {
+    last_completed_migration = completed;
+  }
+}

tests/solidity/suites/exception/migrations/1_initial_migration.js

@@ -0,0 +1,5 @@
+const Migrations = artifacts.require("Migrations");
+
+module.exports = function (deployer) {
+  deployer.deploy(Migrations);
+};

tests/solidity/suites/exception/package.json

@@ -0,0 +1,15 @@
+{
+  "name": "exception",
+  "version": "1.0.0",
+  "author": "huangyi <huang@crypto.com>",
+  "license": "GPL-3.0-or-later",
+  "scripts": {
+    "test-ganache": "yarn truffle test",
+    "test-ethermint": "yarn truffle test --network ethermint"
+  },
+  "devDependencies": {
+    "truffle": "^5.1.42",
+    "truffle-assertions": "^0.9.2",
+    "web3": "^1.2.11"
+  }
+}

tests/solidity/suites/exception/test/revert.js

@@ -0,0 +1,35 @@
+const TestRevert = artifacts.require("TestRevert")
+const truffleAssert = require('truffle-assertions');
+
+async function expectRevert(promise) {
+  try {
+    await promise;
+  } catch (error) {
+    if (error.message.indexOf('revert') === -1) {
+      expect('revert').to.equal(error.message, 'Wrong kind of exception received');
+    }
+    return;
+  }
+  expect.fail('Expected an exception but none was received');
+}
+
+contract('TestRevert', (accounts) => {
+  let revert
+
+  beforeEach(async () => {
+    revert = await TestRevert.new()
+  })
+  it('should revert', async () => {
+      await revert.try_set(10)
+      no = await revert.query_a()
+      assert.equal(no, '0', 'The modification on a should be reverted')
+      no = await revert.query_b()
+      assert.equal(no, '10', 'The modification on b should not be reverted')
+      no = await revert.query_c()
+      assert.equal(no, '10', 'The modification on c should not be reverted')
+
+      await revert.set(10)
+      no = await revert.query_a()
+      assert.equal(no, '10', 'The force set should not be reverted')
+  })
+})

tests/solidity/suites/exception/truffle-config.js

@@ -0,0 +1,17 @@
+module.exports = {
+  networks: {
+    // Development network is just left as truffle's default settings
+    ethermint: {
+      host: "127.0.0.1",     // Localhost (default: none)
+      port: 8545,            // Standard Ethereum port (default: none)
+      network_id: "*",       // Any network (default: none)
+      gas: 5000000,          // Gas sent with each transaction
+      gasPrice: 1000000000,  // 1 gwei (in wei)
+    },
+  },
+  compilers: {
+    solc: {
+      version: "0.8.6",
+    },
+  },
+}

x/evm/keeper/context_stack.go

@@ -0,0 +1,87 @@
+package keeper
+
+import (
+	"fmt"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+)
+
+// cachedContext is a pair of cache context and its corresponding commit method.
+// They are obtained from the return value of `context.CacheContext()`.
+type cachedContext struct {
+	ctx    sdk.Context
+	commit func()
+}
+
+// ContextStack manages the initial context and a stack of cached contexts,
+// to support the `StateDB.Snapshot` and `StateDB.RevertToSnapshot` methods.
+type ContextStack struct {
+	// Context of the initial state before transaction execution.
+	// It's the context used by `StateDB.CommitedState`.
+	initialCtx     sdk.Context
+	cachedContexts []cachedContext
+}
+
+// CurrentContext returns the top context of cached stack,
+// if the stack is empty, returns the initial context.
+func (cs *ContextStack) CurrentContext() sdk.Context {
+	l := len(cs.cachedContexts)
+	if l == 0 {
+		return cs.initialCtx
+	}
+	return cs.cachedContexts[l-1].ctx
+}
+
+// Reset sets the initial context and clear the cache context stack.
+func (cs *ContextStack) Reset(ctx sdk.Context) {
+	cs.initialCtx = ctx
+	if len(cs.cachedContexts) > 0 {
+		cs.cachedContexts = []cachedContext{}
+	}
+}
+
+// IsEmpty returns true if the cache context stack is empty.
+func (cs *ContextStack) IsEmpty() bool {
+	return len(cs.cachedContexts) == 0
+}
+
+// Commit commits all the cached contexts from top to bottom in order and clears the stack by setting an empty slice of cache contexts.
+func (cs *ContextStack) Commit() {
+	// commit in order from top to bottom
+	for i := len(cs.cachedContexts) - 1; i >= 0; i-- {
+		// keep all the cosmos events
+		cs.initialCtx.EventManager().EmitEvents(cs.cachedContexts[i].ctx.EventManager().Events())
+		if cs.cachedContexts[i].commit == nil {
+			panic(fmt.Sprintf("commit function at index %d should not be nil", i))
+		} else {
+			cs.cachedContexts[i].commit()
+		}
+	}
+	cs.cachedContexts = []cachedContext{}
+}
+
+// Snapshot pushes a new cached context to the stack,
+// and returns the index of it.
+func (cs *ContextStack) Snapshot() int {
+	i := len(cs.cachedContexts)
+	ctx, commit := cs.CurrentContext().CacheContext()
+	cs.cachedContexts = append(cs.cachedContexts, cachedContext{ctx: ctx, commit: commit})
+	return i
+}
+
+// RevertToSnapshot pops all the cached contexts after the target index (inclusive).
+// the target should be snapshot index returned by `Snapshot`.
+// This function panics if the index is out of bounds.
+func (cs *ContextStack) RevertToSnapshot(target int) {
+	if target < 0 || target >= len(cs.cachedContexts) {
+		panic(fmt.Errorf("snapshot index %d out of bound [%d..%d)", target, 0, len(cs.cachedContexts)))
+	}
+	cs.cachedContexts = cs.cachedContexts[:target]
+}
+
+// RevertAll discards all the cache contexts.
+func (cs *ContextStack) RevertAll() {
+	if len(cs.cachedContexts) > 0 {
+		cs.RevertToSnapshot(0)
+	}
+}

x/evm/keeper/grpc_query.go

@@ -265,7 +265,7 @@ func (k Keeper) BlockBloom(c context.Context, req *types.QueryBlockBloomRequest)
 	bloom, found := k.GetBlockBloom(ctx, req.Height)
 	if !found {
 		// if the bloom is not found, query the transient store at the current height
-		k.ctx = ctx
+		k.WithContext(ctx)
 		bloomInt := k.GetBlockBloomTransient()
 
 		if bloomInt.Sign() == 0 {
@@ -381,6 +381,7 @@ func (k Keeper) EthCall(c context.Context, req *types.EthCallRequest) (*types.Ms
 	evm := k.NewEVM(msg, ethCfg, params, coinbase)
 	// pass true means execute in query mode, which don't do actual gas refund.
 	res, err := k.ApplyMessage(evm, msg, ethCfg, true)
+	k.ctxStack.RevertAll()
 	if err != nil {
 		return nil, status.Error(codes.Internal, err.Error())
 	}
@@ -443,15 +444,15 @@ func (k Keeper) EstimateGas(c context.Context, req *types.EthCallRequest) (*type
 	executable := func(gas uint64) (bool, *types.MsgEthereumTxResponse, error) {
 		args.Gas = (*hexutil.Uint64)(&gas)
 
-		// Execute the call in an isolated context
-		k.BeginCachedContext()
+		// Reset to the initial context
+		k.WithContext(ctx)
 
 		msg := args.ToMessage(req.GasCap)
 		evm := k.NewEVM(msg, ethCfg, params, coinbase)
 		// pass true means execute in query mode, which don't do actual gas refund.
 		rsp, err := k.ApplyMessage(evm, msg, ethCfg, true)
 
-		k.EndCachedContext()
+		k.ctxStack.RevertAll()
 
 		if err != nil {
 			if errors.Is(stacktrace.RootCause(err), core.ErrIntrinsicGas) {