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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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79 changes: 79 additions & 0 deletions rpc/backend/comet_test.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,79 @@
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
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)
}
})
})
}
}