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Add bytes support for 1 length prefix #18

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Merged
JohnChangUK merged 1 commit into from
Mar 10, 2026
Merged

Add bytes support for 1 length prefix #18

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3 changes: 3 additions & 0 deletions codegen/astgen/v3/common.go
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Original file line number Diff line number Diff line change
Expand Up @@ -216,6 +216,7 @@ func (c *codeGenAst) getTemplates(
RawType: field.String(),
IsOptional: isOptional,
IsEnum: c.isEnumType(typeExtracted, pkg),
IsBytes: model.BytesFieldNames[fieldExtracted],
IsBytesHex: model.BytesHexFieldNames[fieldExtracted],
IsUint32: model.Uint32FieldNames[fieldExtracted],
IsUint32List: model.Uint32ListFieldNames[fieldExtracted],
Expand Down Expand Up @@ -438,6 +439,7 @@ func (c *codeGenAst) getDataTypes(pkg *daml.Package, module *daml.Module, module
Type: typeExtracted,
RawType: field.String(),
IsOptional: isOptional,
IsBytes: model.BytesFieldNames[fieldExtracted],
IsBytesHex: model.BytesHexFieldNames[fieldExtracted],
IsUint32: model.Uint32FieldNames[fieldExtracted],
IsUint32List: model.Uint32ListFieldNames[fieldExtracted],
Expand All @@ -455,6 +457,7 @@ func (c *codeGenAst) getDataTypes(pkg *daml.Package, module *daml.Module, module
Type: typeExtracted,
RawType: field.String(),
IsOptional: true,
IsBytes: model.BytesFieldNames[fieldExtracted],
IsBytesHex: model.BytesHexFieldNames[fieldExtracted],
IsUint32: model.Uint32FieldNames[fieldExtracted],
IsUint32List: model.Uint32ListFieldNames[fieldExtracted],
Expand Down
1 change: 1 addition & 0 deletions codegen/model/template.go
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Expand Up @@ -29,6 +29,7 @@ type TmplField struct {
RawType string
IsOptional bool
IsEnum bool
IsBytes bool // True if field should use uint8 length prefix (hex:"bytes" tag)
IsBytesHex bool // True if field should use uint16 length prefix (hex:"bytes16" tag)
IsUint32 bool // True if INT64 field should encode as 4-byte uint32 (hex:"uint32" tag)
IsUint32List bool // True if []INT64 field should encode with 4-byte uint32 elements (hex:"[]uint32" tag)
Expand Down
27 changes: 27 additions & 0 deletions codegen/model/types.go
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Expand Up @@ -68,6 +68,18 @@ func (t BytesHex) IsBytesHex() bool {
return true
}

// ** Custom Bytes Length Mapping **

// The Daml compiler erases type synonyms. When you define a field as BytesHex in Daml,
// the compiler expands it to its underlying type (Text) in the compiled Daml-LF output.
// By the time go-daml parses the .dalf files, all it sees is
// signerAddress: Text
// operationData: Text
// root: Text
// There's no way to distinguish which Text fields were originally BytesHex and require special encoding.
// The hardcoded maps (BytesFieldNames, BytesHexFieldNames) work around this limitation by explicitly listing
// field names that need hex encoding tags.

// BytesHexFieldNames contains field names that should use uint16 length prefix
// encoding (hex:"bytes16" tag) instead of the default uint8 length prefix.
//
Expand All @@ -87,6 +99,21 @@ var BytesHexFieldNames = map[string]bool{
"salt": true,
}

// BytesFieldNames contains field names that should use uint8 length prefix
// encoding (hex:"bytes" tag). These are fixed-size hex fields ≤255 bytes.
//
// From MCMS/CCIP contracts:
// - signerAddress: EVM signer address (20 bytes)
// - chainFamilySelector: Chain family selector (4 bytes)
// - root: Merkle root hash (32 bytes)
// - newRoot: New merkle root hash (32 bytes)
var BytesFieldNames = map[string]bool{
"signerAddress": true,
"chainFamilySelector": true,
"root": true,
"newRoot": true,
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@RodrigoAD RodrigoAD Mar 10, 2026

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Isn't this very domain (CCIP/MCMS) specific? I see we also have another specific type Uint32ListFieldNames. I feel this shouldn't belong to this lib

}

// Uint32FieldNames contains field names where INT64 should encode as 4-byte uint32.
// This matches the Daml MCMS/Codec.daml encoding which uses encodeUint32 for these fields.
//
Expand Down
4 changes: 2 additions & 2 deletions codegen/source.go.tmpl
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Expand Up @@ -301,7 +301,7 @@ var _ types.ENUM = {{capitalise .Name}}("")
// {{capitalise .Name}} is a {{.RawType}} type
type {{capitalise .Name}} struct {
{{- range $field := .Fields}}
{{capitalise $field.Name}} {{$field.Type.GoType}} `json:"{{$field.Name}}"{{if $field.IsOptional}} hex:"optional"{{else if $field.IsBytesHex}} hex:"bytes16"{{else if $field.IsUint32}} hex:"uint32"{{else if $field.IsUint32List}} hex:"[]uint32"{{end}}`
{{capitalise $field.Name}} {{$field.Type.GoType}} `json:"{{$field.Name}}"{{if $field.IsOptional}} hex:"optional"{{else if $field.IsBytes}} hex:"bytes"{{else if $field.IsBytesHex}} hex:"bytes16"{{else if $field.IsUint32}} hex:"uint32"{{else if $field.IsUint32List}} hex:"[]uint32"{{end}}`
{{- end}}
}

Expand Down Expand Up @@ -359,7 +359,7 @@ func (t *{{capitalise .Name}}) UnmarshalHex(data string) error {
type {{capitalise .Name}}MCMSParams struct {
{{- range .Fields}}
{{- if not (isCallerField .Name)}}
{{capitalise .Name}} {{.Type.GoType}} `json:"{{.Name}}"{{if .IsOptional}} hex:"optional"{{else if .IsBytesHex}} hex:"bytes16"{{else if .IsUint32}} hex:"uint32"{{else if .IsUint32List}} hex:"[]uint32"{{end}}`
{{capitalise .Name}} {{.Type.GoType}} `json:"{{.Name}}"{{if .IsOptional}} hex:"optional"{{else if .IsBytes}} hex:"bytes"{{else if .IsBytesHex}} hex:"bytes16"{{else if .IsUint32}} hex:"uint32"{{else if .IsUint32List}} hex:"[]uint32"{{end}}`
{{- end}}
{{- end}}
}
Expand Down