Proc-macros allow default values without needing to specify a literal. #2543
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This makes it possible to say you want the default value for a type rather than specifying a literal - eg, `#[uniffi(default)]` and similarly for defaults args for functions. Supports named types but it's up to the consumer to ensure they can be created without args. via and fixes mozilla#2538
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Fixes #1653 |
bendk
reviewed
May 27, 2025
| @@ -20,6 +20,15 @@ | |||
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| - HashMaps in UDL now support a default value with an empty map ([#2539](https://github.com/mozilla/uniffi-rs/pull/2539)). | |||
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| XXX - thiss change log is missing 29.2?? | |||
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I think I forgot to open a PR after releasing 0.29.2. Here it is now though.: #2546
bendk
approved these changes
May 27, 2025
| - All builtin types have default values (zero, false, empty) | ||
| - Named types (ie, Records, Objects, etc) are supported, but you must ensure the | ||
| item is able to be created without arguments (eg, has a default constructor | ||
| with no args, is a record with all fields having defaults, etc) |
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Looks right to me, but I think describing 1 type per row would be clearer. It's less compact, but I think it's worth the space. Maybe a table would be better:
| Type | Default value |
|---|---|
Option |
None |
| String | Empty string |
Vec<T> |
Empty list |
HashMap<T> |
Empty map |
| Builtin numeric types | 0 |
bool |
false |
| Records | Record with all fields set to their default value (only valid if they all have defaults) |
| Objects | Primary constructor called with 0 arguments |
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thanks - that just makes the section below this look even worse, but I just opened #2551 instead of getting distracted by that.
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@jplatte @bendk like we spoke about, this seems quite nice to me. It's a breaking change (and I think the changelog is messed up, but we can sort that out)
This makes it possible to say you want the default value for a type rather than specifying a literal - eg,
#[uniffi(default)]and similarly for defaults args for functions.Supports named types but it's up to the consumer to ensure they can be created without args.
via and fixes #2538