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fix(rpc): guard nil height deref in CometBlockResultByNumber #1067

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fix(rpc): guard nil height deref in CometBlockResultByNumber #1067

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3c077ef
fix(rpc): guard nil height deref in CometBlockResultByNumber
Aboudjem Mar 11, 2026
694601d
test: remove unused expectPanic field from test struct
Aboudjem Mar 11, 2026
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2 changes: 1 addition & 1 deletion rpc/backend/comet.go
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Original file line number Diff line number Diff line change
Expand Up @@ -68,7 +68,7 @@ func (b *Backend) CometBlockResultByNumber(ctx context.Context, height *int64) (
}
res, err := b.RPCClient.BlockResults(ctx, height)
if err != nil {
return nil, fmt.Errorf("failed to fetch block result from CometBFT %d: %w", *height, err)
return nil, fmt.Errorf("failed to fetch block result from CometBFT %d: %w", heightAttr, err)
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@greptile-apps greptile-apps bot Mar 11, 2026

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Ambiguous height in error message when caller passes nil

When CometBlockResultByNumber is called with a nil height (i.e., "fetch latest block"), heightAttr defaults to 0. If BlockResults then fails, the error message will read "failed to fetch block result from CometBFT 0: ...", which is indistinguishable from a caller that explicitly requested block 0 (which is also remapped to nil). This is a pre-existing ambiguity but the fix keeps it intact.

Consider using a more descriptive format string to differentiate the two cases, for example:

heightStr := "latest"
if heightAttr != 0 {
    heightStr = fmt.Sprintf("%d", heightAttr)
}
return nil, fmt.Errorf("failed to fetch block result from CometBFT (height=%s): %w", heightStr, err)

This is a minor style concern and does not affect correctness.

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!

}

return res, nil
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80 changes: 80 additions & 0 deletions rpc/backend/comet_test.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,80 @@
package backend

import (
"context"
"errors"
"testing"

"github.com/stretchr/testify/mock"
"github.com/stretchr/testify/require"

tmrpctypes "github.com/cometbft/cometbft/rpc/core/types"

"github.com/cosmos/evm/rpc/backend/mocks"
)

func TestCometBlockResultByNumber_NilHeightErrorPath(t *testing.T) {
testCases := []struct {
name string
height *int64
rpcErr error
expectPanic bool
expectErr bool
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@greptile-apps greptile-apps bot Mar 11, 2026

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Unused struct field expectPanic

The expectPanic field is declared in the test case struct but is never read or used anywhere in the test body. All cases rely on require.NotPanics to assert no panic, and none of the test cases even set expectPanic: true. This dead field is misleading — a future maintainer might assume it drives some assertion when it does not.

Either remove the field or wire it up to an actual require.Panics / require.NotPanics branch:

Suggested change
expectPanic bool
expectErr bool
testCases := []struct {
name string
height *int64
rpcErr error
expectErr bool
}{

}{
{
name: "nil height, BlockResults succeeds",
height: nil,
rpcErr: nil,
expectErr: false,
},
{
name: "non-zero height, BlockResults succeeds",
height: func() *int64 { h := int64(5); return &h }(),
rpcErr: nil,
expectErr: false,
},
{
name: "zero height remapped to nil, BlockResults errors - must not panic",
height: func() *int64 { h := int64(0); return &h }(),
rpcErr: errors.New("connection timeout"),
expectErr: true,
},
{
name: "nil height, BlockResults errors",
height: nil,
rpcErr: errors.New("pruned state"),
expectErr: true,
},
}

for _, tc := range testCases {
t.Run(tc.name, func(t *testing.T) {
backend := setupMockBackend(t)
mockClient := backend.ClientCtx.Client.(*mocks.Client)

// The function remaps height=0 to nil before calling BlockResults,
// so always mock with nil when input is 0.
var mockHeight *int64
if tc.height != nil && *tc.height != 0 {
mockHeight = tc.height
}

if tc.rpcErr != nil {
mockClient.On("BlockResults", mock.Anything, mockHeight).
Return((*tmrpctypes.ResultBlockResults)(nil), tc.rpcErr).Once()
} else {
mockClient.On("BlockResults", mock.Anything, mockHeight).
Return(&tmrpctypes.ResultBlockResults{Height: 1}, nil).Once()
}

require.NotPanics(t, func() {
_, err := backend.CometBlockResultByNumber(context.Background(), tc.height)
if tc.expectErr {
require.Error(t, err)
} else {
require.NoError(t, err)
}
})
})
}
}