Crate activitystreams

ActivityStreams

A set of Traits and Types that make up the ActivityStreams and ActivityPub specifications

Usage

First, add ActivityStreams to your dependencies

activitystreams = "0.6.2"

Types

The project is laid out by Kind => Type

So to use an ActivityStreams Video, you'd write

use activitystreams::object::Video;

And to use an ActivityStreams profile, you'd write

use activitystreams::object::Profile;

Properties

Each concrete type implements AsRef<> for each of their properties fields. A basic ActivityStreams object will implement AsRef<ObjectProperties>.

The Properties types can be found near the kind they're associated with. ObjectProperties and ApObjectProperties are located in activitystreams::object::properties.

The Properties types are generated by the properties macro, which attempts to create fields that represent exactly the bounds of the ActivityStreams and ActivityPub specifications.

For example, the Object type in ActivityStreams has a summary field, which can either be represented as an xsd:string or an rdf:langString. It also states that the summary field is not functional, meaning that any number of xsd:string or rdf:langString, or a combination thereof, can be present. To represent this, the properties macro generates a couple enum types.

First, it generates ObjectPropertiesSummaryTermEnum, which is a "terminating" enum. "terminating" in this context means it is the smallest unit of the type. This enum has two variants, named after the types they contain, XsdString(...) and RdfLangString(...).

Next, it generates ObjectPropertiesSummaryEnum, which contains two variants, Term(...) and Array(...). The Term variant contains an ObjectPropertiesSummaryTermEnum, and the Array variant contains a Vec<ObjectPropertiesSummaryTermEnum>.

Finally, when declaring the field, it generates summary: Option<ObjectPropertiesSummaryEnum>, since summary is not a required field.

This resulting type is exactly specific enough to match the following valid ActivityStreams json, without matching any invalid json.

With no summary:

{}

With a sring summary:

{
    "summary": "A string"
}

With an rdf langstring

{
    "summary": {
        "@value": "A string",
        "@language": "en"
    }
}

With multiple values

{
    "summary": [
        {
            "@value": "A string",
            "@language": "en"
        },
        "An xsd:string this time"
    ]
}

It may seem like interacting with these types might get unweildy, so the properties macro also generates methods for interacting with each field.

fn set_summary_xsd_string<T>(&mut self, T) -> Result<...>;
fn set_summary_rdf_lang_string<T>(&mut self, T) -> Result<...>;
fn set_many_summary_xsd_strings<T>(&mut self, Vec<T>) -> Result<...>;
fn set_many_summary_rdf_lang_strings<T>(&mut self, Vec<T>) -> Result<...>;

fn delete_summary(&mut self) -> &mut Self;

fn get_summary_xsd_string(&self) -> Option<XsdString>;
fn get_summary_rdf_lang_string(&self) -> Option<RdfLangString>;
fn get_many_summary_xsd_strings(&self) -> Option<Vec<&XsdString>>;
fn get_many_summary_rdf_lang_strings(&self) -> Option<Vec<&RdfLangString>>;

These methods provide access to setting and fetching uniformly typed data, as well as deleting the data. In the setter methods, the type parameter T is bound by TryInto<XsdString> or TryInto<RdfLangString>. This allows passing values to the method that can be converted into the types, rather than requiring the caller to perform the conversion.

Types like XsdString and RdfLangString can be found in the primitives module. Unless you're building your own custom types, you shouldn't need to import them yourself. They each implement FromStr for parsing and Display to convert back to strings, as well as From and Into or TryFrom and TryInto for types you might expect them to (e.g. XsdNonNegativeInteger implements From<u64> and Into<u64>).

For some fields, like id, there is only one valid type. methods generated for fields like these will leave out the type name from the function name.

fn set_id<T>(&mut self, T) -> Result<...>;
fn delete_id(&mut self) -> &mut Self;
fn get_id(&self) -> Option<XsdAnyUri>;

Traits

This library provides a number of traits, such as Object, Link, Actor, Activity, Collection, and CollectionPage. The majority of these traits exist solely to "mark" types, meaning they don't provide value, at runtime, but exist to add constraints to generics at compiletime.

If you want to make a function that manipulates an Activity, but not a normal object, you could bound the function like so:

fn my_manipulator<T>(some_activity: T) -> Result<&mut ObjectProperties, SomeErrorType>
where
    T: Activity + AsMut<ObjectProperties>,
{
    some_activity.as_mut().set_whatever_tbh()
}

Kinds

This library has a set of unit structs that serialize and deserialize to strings. This is to enable different ActivityPub Object types to be deserialized into different Named structs. These can be found in activitystreams::objects::kind, and similar paths.

To build your own Person struct, for example, you could write

use activitystreams::actor::kind::PersonType;

#[derive(serde::Deserialize, serde::Serialize)]
pub struct MyPerson {
    // Do a rename since `type` is not a valid rust field name
    #[serde(rename = "type")]
    kind: PersonType,
}

And this type would only deserialize for JSON where "type":"Person"

Extensions

In some cases, like when dealing with ActivityPub, it is neccessary to extend the ActivityStreams specification. For this purpose, two traits and a type have been introduced.

use activitystreams::ext::{Ext, Extensible, Extension};

The Ext type is a simple record containing first, the ActivityStreams type, and second, the extension to that type.

There are two provided extensions in the ActivityStreams library.

• ApObjectProperties, extra properties for all ActivityStreams objects in the ActivityPub spec
• ApActorProperties, extra properties specifically for Actors in the ActivityPub spec

To use an object with its default extensions, the object's full() associated function may be invoked.

let video_with_extensions = Video::full();

Features

There are a number of features that can be disabled in this crate. By default, everything is enabled.

activitystreams = { version = "0.6.2", default-features = "false", features = ["derive"] }

feature	what you get
none	Just the Marker Traits
derive	Marker Traits + derive macros from activitystreams-derive
kinds	Marker Traits + derive macros + Kind UnitStructs
primitives	Marker Traits + Primitive values
types	Everything, this is the default

Examples

Basic

use activitystreams::object::{Video, properties::ObjectProperties};
use anyhow::Error;

// We perform configuration in a dedicated function to specify which Properties type we want to
// perform the operations on.
fn configure_video(mut v: impl AsMut<ObjectProperties>) -> Result<(), Error> {
    v.as_mut()
        .set_context_xsd_any_uri("https://www.w3.org/ns/activitystreams")?
        .set_id("https://example.com/@example/lions")?
        .set_url_xsd_any_uri("https://example.com/@example/lions/video.webm")?
        .set_name_xsd_string("My Cool Video")?
        .set_summary_xsd_string("A video about some cool lions")?
        .set_media_type("video/webm")?
        .set_duration("PT4M20S")?;

    Ok(())
}

fn main() -> Result<(), Error> {
    let mut v = Video::default();

    configure_video(&mut v)?;

    println!("Video, {:#?}", v);

    let s = serde_json::to_string(&v)?;

    println!("json, {}", s);

    let v: Video = serde_json::from_str(&s)?;

    println!("Video again, {:#?}", v);

    Ok(())
}

Intermediate

use activitystreams::{
    context,
    actor::{Actor, ActorBox},
    ext::Ext,
    object::{
        properties::{
            ObjectProperties,
            ProfileProperties
        },
        Profile,
        Object,
        ObjectBox,
    },
    primitives::XsdAnyUri,
    Base, BaseBox, PropRefs,
};
use serde::{Deserialize, Serialize};

#[derive(Clone, Debug, Default, Deserialize, Serialize, PropRefs)]
#[serde(rename_all = "camelCase")]
#[prop_refs(Object)]
#[prop_refs(Actor)]
pub struct Persona {
    #[serde(rename = "@context")]
    context: XsdAnyUri,

    #[serde(rename = "type")]
    kind: String,
}

fn main() -> Result<(), anyhow::Error> {
    let mut profile = Profile::full();

    let pprops: &mut ProfileProperties = profile.as_mut();

    pprops.set_describes_object_box(Persona {
        context: context(),
        kind: "Persona".to_owned(),
    })?;

    let oprops: &mut ObjectProperties = profile.as_mut();
    oprops.set_context_xsd_any_uri(context())?;

    let profile_string = serde_json::to_string(&profile)?;

    let profile: Profile = serde_json::from_str(&profile_string)?;

    Ok(())
}

Advanced

use activitystreams::{
    properties,
    ext::Ext,
    link::{
        properties::LinkProperties,
        Link, LinkBox, Mention,
    },
    Base, BaseBox, PropRefs,
    UnitString,
};
use serde::{Deserialize, Serialize};

/// Using the UnitString derive macro
///
/// This macro implements Serialize and Deserialize for the given type, making this type
/// represent the string "MyLink" in JSON.
#[derive(Clone, Debug, Default, UnitString)]
#[unit_string(MyLink)]
pub struct MyKind;

properties! {
    My {
        docs [ "Defining our own properties struct called MyProperties" ],

        required_key {
            docs [
                "Our own required key field",
                "",
                "'types' defines the range of values that can be stored in required_key",
                "",
                "'functional' means there is at most one value for required_key",
                "'required' means there is at least one value for required_key",
            ],
            types [ String ],
            functional,
            required,
        },
    }
}

#[derive(Clone, Debug, Default, serde::Serialize, serde::Deserialize)]
#[serde(transparent)]
pub struct MyLinkProps(pub LinkProperties);

/// Using the Properties derive macro
///
/// This macro generates getters and setters for the associated fields.
#[derive(Clone, Debug, Default, Deserialize, Serialize, PropRefs)]
#[serde(rename_all = "camelCase")]
#[prop_refs(Link)]
pub struct My {
    /// Use the UnitString MyKind to enforce the type of the object by "MyLink"
    pub kind: MyKind,

    /// Derive AsRef/AsMut for My -> MyProperties
    #[prop_refs]
    pub my_properties: MyProperties,

    /// Derive AsRef/AsMut/Link for My -> MyLinkProperties
    #[prop_refs]
    pub link_properties: MyLinkProps,
}

fn main() -> Result<(), anyhow::Error> {
    let mut my_link = My::default();

    let lprops: &mut MyProperties = my_link.as_mut();
    lprops.set_required_key("Hey")?;

    let my_link_string = serde_json::to_string(&my_link)?;

    let my_link: My = serde_json::from_str(&my_link_string)?;

    Ok(())
}

Re-exports

pub use self::activity::Activity;

pub use self::activity::IntransitiveActivity;

pub use self::actor::Actor;

pub use self::collection::Collection;

pub use self::collection::CollectionPage;

pub use self::link::Link;

pub use self::object::Object;

Modules

activity	Namespace for Activity types
actor	Namespace for Actor types
collection	Namespace for Collection types
endpoint	Endpoint traits and types
ext	Defining extensibility in the ActivityStreams spec
link	Namespace for Link types
object	Namespace for Object types
primitives	Types defined as 'primitives' are used as building-blocks for ActivityStreams objects.

Macros

properties

Generate structs and enums for activitystreams objects

Structs

BaseBox

A wrapper type around a generic Base

Traits

Base	The lowermost trait of the trait structure

Functions

context	The context associated with all of the Activity Streams types defined in the crate.
public	The 'public' actor, doesn't denote a real actor but describes a publicly available object.
security	The 'security' extension used by some implementations

Attribute Macros

wrapper_type

Derive a wrapper type based on serde_json::Value to contain any possible trait type

Derive Macros

Extensible	Generate a type with default extensions
PropRefs	Derive implementations for activitystreams objects
UnitString	Derive implementations Serialize and Deserialize for a constant string Struct type