Remove IGNORE_IF_DEFAULT_VALUE

[timostamm]

The option (buf.validate.field).ignore = IGNORE_IF_DEFAULT_VALUE disables validation rules for a field, depending on the value of the field: If the value equals the default value, rules are ignored.

We've found that this option overlaps with IGNORE_IF_UNPOPULATED for fields with implicit presence, and that the exact conditions for validation to apply are quite difficult to understand just from looking at a message definition.

To ensure that Protovalidate rules are easy to understand for authors and consumers, we are removing the option. This is a breaking change.

Updating your rules to this change is likely as simple as switching to IGNORE_IF_ZERO_VALUE (renamed from IGNORE_IF_UNPOPULATED in #397):

syntax="proto3";
message Example {
  string email = 1 [
    (buf.validate.field).string.email = true,
-   (buf.validate.field).ignore = IGNORE_IF_DEFAULT_VALUE
+   (buf.validate.field).ignore = IGNORE_IF_ZERO_VALUE
  ];
}

For proto3 string, bool, bytes, int32, and other numeric fields, as well as repeated fields and map fields, IGNORE_IF_ZERO_VALUE behaves the same as IGNORE_IF_DEFAULT_VALUE. For other fields, we recommend that you switch to CEL to express the exact requirements, which will improve the readability of your schema constraints.

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	⏩ skipped	Jul 15, 2025, 11:33 AM