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Document that its intentional that Rust Protobuf does not generate a set_foo_opt() setter. #330

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copybara-service merged 1 commit into from
Sep 28, 2026
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Document that its intentional that Rust Protobuf does not generate a set_foo_opt() setter. #330

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15 changes: 14 additions & 1 deletion content/reference/rust/rust-generated.md
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Expand Up @@ -218,6 +218,18 @@ Presence is set using the
[`features.field_presence`](/editions/features#field_presence)
option in editions.

**Note:** While fields with explicit presence provide a `foo_opt()` getter that
returns an `Option`, we do not generate a corresponding `set_foo_opt()` setter.
An operation to "set or maybe clear a field" is considered to be a rare notion
that is better being "visible" at the caller that it is doing one of two
possible mutations (`set_foo` or `clear_foo`). Additionally, the raw code size
of our gencode is a concern so adding further cases for rare operations is
considered not worth the growth. However, we know this API asymmetry with having
an `opt` getter is awkward and may revisit if this operation proves to be
sensible and not rare in the future.
[No Nullable Setters/Getters Support](/design-decisions/nullable-getters-setters)
is related.

#### Numeric Fields {#numeric-fields}

For this field definition:
Expand Down Expand Up @@ -446,7 +458,8 @@ The compiler generates the following accessor methods:
* `fn has_foo(&self) -> bool`: Returns `true` if the field is set.
* `fn clear_foo(&mut self)`: Clears the value of the field. After calling
this, `has_foo()` returns `false` and `foo()` returns the default value.
Cords have not been implemented yet.
Cords have not been implemented
yet.

For fields of type `bytes` the compiler generates the `ProtoBytesCow` type
instead.
Expand Down
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