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Fix field default for bytes #689

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Merged
doriable merged 3 commits into from
Mar 23, 2026
+28 −10
Merged

Fix field default for bytes #689

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5db0781
Fix default values for bytes fields
doriable Mar 19, 2026
aa15cd6
Add test case
doriable Mar 19, 2026
ffc87ae
Add reference to docs on default value encoding
doriable Mar 20, 2026
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12 changes: 11 additions & 1 deletion experimental/fdp/generator.go
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
package fdp

import (
"bytes"
"math"
"slices"
"strconv"
Expand Down Expand Up @@ -577,7 +578,16 @@ func (g *generator) field(f ir.Member, fdp *descriptorpb.FieldDescriptorProto, s
fdp.DefaultValue = addr(strconv.FormatFloat(v, 'g', -1, 64))
}
} else if v, ok := d.AsString(); ok {
fdp.DefaultValue = addr(v)
if fdp.GetType() == descriptorpb.FieldDescriptorProto_TYPE_BYTES {
// For bytes fields, the default value needs to be escaped.
// Reference for default value encoding:
// https://protobuf.com/docs/descriptors#encoding-default-values
var buf bytes.Buffer
internal.WriteEscapedBytes(&buf, []byte(v))
fdp.DefaultValue = addr(buf.String())
} else {
fdp.DefaultValue = addr(v)
}
}

g.addSourceLocationWithSourcePathElements(
Expand Down
2 changes: 2 additions & 0 deletions experimental/ir/testdata/fields/default.proto
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Expand Up @@ -43,6 +43,8 @@ message M {
bool b2 = 32 [default = 1];
bool b3 = 33 [default = false];

bytes b = 40 [default = "\0\1\2\3\4\5\6\7fubar!"];

enum E {
E0 = 0;
E1 = 1;
Expand Down
6 changes: 6 additions & 0 deletions experimental/ir/testdata/fields/default.proto.fds.yaml
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Expand Up @@ -116,6 +116,12 @@ file:
type: TYPE_BOOL
default_value: "false"
json_name: "b3"
- name: "b"
number: 40
label: LABEL_OPTIONAL
type: TYPE_BYTES
default_value: "\\000\\001\\002\\003\\004\\005\\006\\007fubar!"
json_name: "b"
- name: "e1"
number: 41
label: LABEL_OPTIONAL
Expand Down
18 changes: 9 additions & 9 deletions experimental/ir/testdata/fields/default.proto.stderr.txt
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Expand Up @@ -109,40 +109,40 @@ warning: redundant custom default
making this option redundant

warning: redundant custom default
--> testdata/fields/default.proto:53:26
--> testdata/fields/default.proto:55:26
|
53 | E e3 = 43 [default = E0];
55 | E e3 = 43 [default = E0];
| ^^ this is the zero value for `buf.test.M.E`
|
= help: fields without a custom default will default to the zero value,
making this option redundant

error: expected singular scalar- or enum-typed field, found scalar type `int32`
--> testdata/fields/default.proto:55:14
--> testdata/fields/default.proto:57:14
|
55 | repeated int32 w1 = 101 [default = 1, default = 2];
57 | repeated int32 w1 = 101 [default = 1, default = 2];
| ^^^^^ ------- custom default specified here
|
= help: custom defaults are only for non-repeated fields that have a
non-message type

error: expected singular scalar- or enum-typed field, found message type
`buf.test.M`
--> testdata/fields/default.proto:56:5
--> testdata/fields/default.proto:58:5
|
56 | M w2 = 102 [default = {
58 | M w2 = 102 [default = {
| ^ ------- custom default specified here
|
= help: custom defaults are only for non-repeated fields that have a
non-message type

error: expected singular scalar- or enum-typed field, found message type
`buf.test.M`
--> testdata/fields/default.proto:60:5
--> testdata/fields/default.proto:62:5
|
60 | M w3 = 103 [
62 | M w3 = 103 [
| ^
61 | default.i1 = 42,
63 | default.i1 = 42,
| ------- custom default specified here
|
= help: custom defaults are only for non-repeated fields that have a
Expand Down
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