What's so hard about writing a Slack client in Rust?

"I'll just write a simple API wrapper for that. Give me two hours." Does that sound oddly familiar? Don't be fooled: writing an easy to use, idiomatic abstraction layer is a lot of work - in any language. I want to tell you my story about writing a Slack client in Rust. From documentation to testing and error handling there's a lot of pitfalls to avoid and laughs to share.

The talk is pretty lighthearted. I want to show that mere mortals like myself can be productive and have fun with Rust.

Transcript

1. What’s so hard
   about wri/ng a
   Slack Client
   in Rust?
   

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2. @magithub.com/mre
   

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3. Mo/va/on
   

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4. 120 Million monthly users

   3 Billion requests / month

   lots of data

   lots of services
   

   1200 employees

   all using Slack
   

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5. Write bots! (Chatops)
   Collect metrics! (Messages per day…)
   Clone Alien-Dinosaurs!
   Have fun!
   

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7. 2 Million!!!!11!
   Jan 2016
   

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11. To create a

    Slack bot
    we need a

    Slack client
    (d’oh)
    

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12. slack-rs-api

    example
    Holy Batman…
    Pass client and token

    with every request?
    ಠ_ಠ
    

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14. What could be
    improved?
    •Documenta/on:

    Some/mes the only way to make things
    working

    is to look at the source code
    •Not idioma/c:

    Code doesn’t feel ergonomic/rus/c
    •No tests
    •…
    

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15. wat
    if I create one?
    

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16. Goals
    

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17. Goals
    Great ergonomics. Easy to use!
    Pure, idioma/c Rust code.
    Fully documented and tested.
    Solid error handling.
    Convert from JSON to seman/c types.
    Full Slack API implementa/on.
    

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18. Topics
    1. Idioma/c Rust: Builder pa2. Tes/ng: yup-hyper-mock
    3. Error handling: error_chain
    4. JSON to seman/c types: serde_json
    5. Full Slack API: json schema
    

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19. Idioma/c Rust

    Using the Builder pa1. Do_it_yourself
    2. derive_builder
    https://aturon.github.io/ownership/builders.html
    

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20. h/github.com/colin-kiegel/rust-derive-builder/issues/31
    

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23. Error handling
    

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24. error_chain
    

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25. error_chain
    

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26. error_chain
    

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27. error_chain
    

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28. Tes/ng
    yup_hyper_mock
    

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30. Code genera/on
    

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31. Group: "dnd"
    Method: "dnd.endSnooze"
    Method: "dnd.setSnooze"
    Method: "dnd.endDnd"
    Method: "dnd.info"
    Method: "dnd.teamInfo"
    Group: "search"
    Method: "search.messages"
    Method: "search.files"
    Method: "search.all"
    Group: "api"
    Method: "api.test"
    Group: "auth"
    Method: "auth.test"
    Method: "auth.revoke"
    Group: "users"
    Method: "users.info"
    Method: "users.setPresence"
    Method: "users.setPhoto"
    Method: "users.profile.set"
    Method: "users.deletePhoto"
    Method: "users.profile.get"
    Method: "users.setAc/ve"
    Method: "users.list"
    Method: "users.iden/ty"
    Method: "users.getPresence"
    Group: "reac/ons"
    Method: "reac/ons.add"
    Method: "reac/ons.list"
    Method: "reac/ons.remove"
    Method: "reac/ons.get"
    Group: "oauth"
    Method: "oauth.access"
    Group: "stars"
    Method: "stars.add"
    Method: "stars.list"
    Method: "stars.remove"
    Group: "files"
    Method: "files.upload"
    Method: "files.list"
    Method: "files.sharedPublicURL"
    Method: "files.revokePublicURL"
    Method: "files.comments.delete"
    Method: "files.delete"
    Method: "files.comments.edit"
    Method: "files.info"
    Method: "files.comments.add"
    Group: "bots"
    Method: "bots.info"
    Group: "im"
    Method: "im.replies"
    Method: "im.mark"
    Method: "im.history"
    Method: "im.open"
    Method: "im.close"
    Method: "im.list"
    Group: "pins"
    Method: "pins.list"
    Method: "pins.add"
    Method: "pins.remove"
    Group: "mpim"
    Method: "mpim.history"
    Method: "mpim.mark"
    Method: "mpim.list"
    Method: "mpim.close"
    Method: "mpim.open"
    Method: "mpim.replies"
    Group: "channels"
    Method: "channels.mark"
    Method: "channels.list"
    Method: "channels.kick"
    Method: "channels.rename"
    Method: "channels.create"
    Method: "channels.setPurpose"
    Method: "channels.history"
    Method: "channels.unarchive"
    Method: "channels.join"
    Method: "channels.archive"
    Method: "channels.replies"
    Method: "channels.info"
    Method: "channels.setTopic"
    Method: "channels.leave"
    Method: "channels.invite"
    Group: "emoji"
    Method: "emoji.list"
    Group: "groups"
    Method: "groups.setTopic"
    Method: "groups.history"
    Method: "groups.unarchive"
    Method: "groups.leave"
    Method: "groups.create"
    Method: "groups.createChild"
    Method: "groups.archive"
    Method: "groups.kick"
    Method: "groups.setPurpose"
    Method: "groups.list"
    Method: "groups.invite"
    Method: "groups.open"
    Method: "groups.mark"
    Method: "groups.close"
    Method: "groups.replies"
    Method: "groups.rename"
    Method: "groups.info"
    Group: "usergroups"
    Method: "usergroups.create"
    Method: "usergroups.list"
    Method: "usergroups.users.u
    Method: "usergroups.disable
    Method: "usergroups.update
    Method: "usergroups.users.li
    Method: "usergroups.enable
    Group: "reminders"
    Method: "reminders.add"
    Method: "reminders.info"
    Method: "reminders.list"
    Method: "reminders.delete"
    Method: "reminders.complet
    Group: "rtm"
    Method: "rtm.start"
    Group: "team"
    Method: "team.accessLogs"
    Method: "team.billableInfo"
    Method: "team.integra/onLo
    Method: "team.info"
    Method: "team.profile.get"
    Group: "chat"
    Method: "chat.postMessage"
    Method: "chat.update"
    Method: "chat.meMessage"
    Method: "chat.delete"
    

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32. Slack
    build.rs
    Main Rust crate
    codegen
    build.rs
    Helper Rust crate
    Slack API ref
    Ruby rake
    h/api.slack.com/methods
    

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33. let mut slack = Client::new("token");
    let response = slack.im_history("channel_name")

    .with_latest(123.1)

    .send();
    Slack client usage
    

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34. let mut slack = Client::new("token");
    let response = slack.send( history::HistoryOptions {
    channel: "hello",
    inclusive: Some(true),
    ..Default::default()
    };
    Slack client usage

    (alterna/ve)
    

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35. Some(ImHistory {
    ok: true,
    latest: None,
    messages: vec![Message {
    msg_type: MessageType::Message,
    ts: 1358546515.000008,
    user: Some("U2147483896".to_string()),
    text: Some("Hello".to_string()),
    is_starred: false,
    wibblr: false,
    reactions: vec![],
    },
    // ...
    Message {
    msg_type: MessageType::Im,
    ts: 1358546515.000007,
    user: None,
    text: None,
    is_starred: false,
    wibblr: true,
    reactions: vec![],
    }],
    has_more: false,
    })
    Result
    

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36. Lessons learned
    Doing anything right is hard

    Doing anything right takes /me

    

    Simple things are difficult
    

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37. Outlook
    

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38. Outlook
    • Support Real/me Slack API
    • Convert all Slack types to Rust
    (Slack::Emoji, Timestamp,…)
    • Iterators for pagina/on
    • Proper into conversions
    • Just read Pascal’s Blog.

    h/scribbles.pascalhertleif.de/
    elegant-apis-in-rust.html
    

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