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Fixing intermittent error experienced with union types #298

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Merged
rockwotj merged 3 commits into from
Oct 22, 2025
Merged

Fixing intermittent error experienced with union types #298

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5c1cfa5
Fixing intermittent error experienced since upgrading to version > 2.…
passuied Oct 22, 2025
46a0328
Adding a unit test to show how to reproduce the issue and proving tha…
passuied Oct 22, 2025
fa888f7
extracted `sortedCopy` method to avoid duplication
passuied Oct 22, 2025
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17 changes: 11 additions & 6 deletions union.go
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Original file line number Diff line number Diff line change
Expand Up @@ -327,7 +327,7 @@ func buildCodecForTypeDescribedBySliceTwoWayJSON(st map[string]*Codec, enclosing
}

func checkAll(allowedTypes []string, cr *codecInfo, buf []byte) (interface{}, []byte, error) {
for _, name := range cr.allowedTypes {
for _, name := range allowedTypes {
if name == "null" {
// skip null since we know we already got type float64
continue
Expand Down Expand Up @@ -399,17 +399,22 @@ func nativeAvroFromTextualJSON(cr *codecInfo) func(buf []byte) (interface{}, []b
// int
// intNativeFromTextual

// sorted so it would be
// double, float, int, long
// that makes the priorities right by chance
sort.Strings(cr.allowedTypes)
// Sort a local copy to avoid mutating cr.allowedTypes shared state
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@passuied passuied Oct 22, 2025 •
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I found that union handling was mutating shared cr.allowedTypes and checkAll iterated over it instead of its parameter, which could cause wrong branch labels like "null" instead of "long".
As a result:

  • Use the allowedTypes parameter inside checkAll.
  • Stop sorting cr.allowedTypes and instead create a local copy to use inside checkAll

local := make([]string, len(allowedTypes))
copy(local, allowedTypes)
sort.Strings(local)
allowedTypes = local

case map[string]interface{}:

// try to decode it as a map
// because a map should fail faster than a record
// if that fails assume record and return it
sort.Strings(cr.allowedTypes)
// Sort a local copy to avoid mutating cr.allowedTypes shared state
local := make([]string, len(allowedTypes))
copy(local, allowedTypes)
sort.Strings(local)
allowedTypes = local
}

return checkAll(allowedTypes, cr, buf)
Expand Down