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Attribute macro to skip serializing all fields of Option type #18

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dtolnay opened this issue Jan 22, 2019 · 4 comments · Fixed by #31
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Attribute macro to skip serializing all fields of Option type #18

dtolnay opened this issue Jan 22, 2019 · 4 comments · Fixed by #31

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@dtolnay
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dtolnay commented Jan 22, 2019

Some JSON workflows involve practically every piece of data being nullable and none of then being serialized when null. The Serde attributes in this situation can be verbose and distracting.

#[derive(Serialize)]
struct Data {
    id: u64,
    #[serde(skip_serializing_if = "Option::is_none")]
    a: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    b: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    c: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    d: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    e: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    f: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    g: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    h: Option<String>,
}

It would be better to have an attribute macro that finds all fields of type Option<_> and inserts a skip_serializing_if attribute.

#[skip_serializing_null]
#[derive(Serialize)]
struct Data {
    id: u64,
    a: Option<String>,
    b: Option<String>,
    c: Option<String>,
    d: Option<String>,
    e: Option<String>,
    f: Option<String>,
    g: Option<String>,
    h: Option<String>,
}

Optionally consider supporting an attribute to annotate optional fields that always need to be serialized, even when null.

#[skip_serializing_null]
#[derive(Serialize)]
struct Data {
    id: u64,
    #[always]
    a: Option<String>,
    b: Option<String>,
    /* ... */
}
@dtolnay dtolnay mentioned this issue Jan 22, 2019
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jonasbb added a commit to jonasbb/serde_with that referenced this issue Mar 19, 2019
@jonasbb
Add a proc_macro component to serde_with
41817e5 
A proc_macro is required to implement skip_serializing_null from
dtolnay/request-for-implementation#18
@jonasbb jonasbb mentioned this issue Mar 19, 2019
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@jonasbb
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jonasbb commented Mar 19, 2019 •
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I'm tackling this issue over at jonasbb/serde_with#46

EDIT: This feature is included in version 1.3.0 of serde_with.

jonasbb added a commit to jonasbb/serde_with that referenced this issue Mar 31, 2019
@jonasbb
Add a proc_macro component to serde_with
fb20c9f 
A proc_macro is required to implement skip_serializing_null from
dtolnay/request-for-implementation#18

Expose the macro crate in serde_with

* Add a "macros"-feature to disable compiling proc_macros
* Add the feature to the testing matrix
bors bot added a commit to jonasbb/serde_with that referenced this issue Mar 31, 2019
@bors @jonasbb
Merge #46
386022c 
46: Add a `skip_serializing_null` attribute r=jonasbb a=jonasbb

The `skip_serializing_null` attribute can be added to any struct and adds `#[serde(skip_serializing_if = "Option::is_none")]` to every `Option` field.
The intended use is for parsing data, e.g., from APIs, which has many optional values.

It turns

```rust
#[skip_serializing_null]
#[derive(Serialize)]
struct Data {
    a: Option<String>,
    b: Option<String>,
    c: Option<String>,
    d: Option<String>,
}
```

into

```rust
#[derive(Serialize)]
struct Data {
    #[serde(skip_serializing_if = "Option::is_none")]
    a: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    b: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    c: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    d: Option<String>,
}
```

The issue was originally suggested at dtolnay/request-for-implementation#18.

# Missing

* [x] Is `skip_serializing_null` the best name? That is how serde or JSON name the empty value, in Rust it is none.
* [x] Support tuple structs
* [x] Support enums
* [x] Handle existing `skip_serializing_if` annotations, by skipping those fields
* [x] Support an additional attribute, which ensures the field is always serialized
* [x] Write compile tests, which ensure the correct error message
* [x] Write documentation for the feature

Co-authored-by: Jonas Bushart <[email protected]>
bors bot added a commit to jonasbb/serde_with that referenced this issue Apr 2, 2019
@bors @jonasbb
Merge #46
bfae055 
46: Add a `skip_serializing_null` attribute r=jonasbb a=jonasbb

The `skip_serializing_null` attribute can be added to any struct and adds `#[serde(skip_serializing_if = "Option::is_none")]` to every `Option` field.
The intended use is for parsing data, e.g., from APIs, which has many optional values.

It turns

```rust
#[skip_serializing_null]
#[derive(Serialize)]
struct Data {
    a: Option<String>,
    b: Option<String>,
    c: Option<String>,
    d: Option<String>,
}
```

into

```rust
#[derive(Serialize)]
struct Data {
    #[serde(skip_serializing_if = "Option::is_none")]
    a: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    b: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    c: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    d: Option<String>,
}
```

The issue was originally suggested at dtolnay/request-for-implementation#18.

# Missing

* [x] Is `skip_serializing_null` the best name? That is how serde or JSON name the empty value, in Rust it is none.
* [x] Support tuple structs
* [x] Support enums
* [x] Handle existing `skip_serializing_if` annotations, by skipping those fields
* [x] Support an additional attribute, which ensures the field is always serialized
* [x] Write compile tests, which ensure the correct error message
* [x] Write documentation for the feature

Co-authored-by: Jonas Bushart <[email protected]>
@jonathan-s
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Looks like this feature is completed, no?

@Warfields
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???

@DrSensor
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I think this already shipped in the current crate serde_with. I've used it and it works as expected. The only thing missing is the documentation 🤔

@jonathan-s jonathan-s mentioned this issue Jun 19, 2019
Merged
dtolnay added a commit that referenced this issue Jun 19, 2019
@dtolnay
Merge pull request #31 from jonathan-s/patch-1
bea70a5 
Issue #18 completed with serde_with
@sssilver sssilver mentioned this issue Aug 20, 2019
Merged
@gabbifish gabbifish mentioned this issue Aug 20, 2019
Merged
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Issue #18 completed with serde_with jonathan-s/request-for-implementation
5 participants
@jonasbb @dtolnay @jonathan-s @DrSensor @Warfields