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1use serde::de::DeserializeOwned;
2use serde::de::value::UnitDeserializer;
3use serde::{Deserialize, Deserializer, Serialize, Serializer};
4
5#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
6#[serde(rename_all = "snake_case")]
7pub enum FailureCode {
8 NotFound,
9 Forbidden,
10 Unauthenticated,
11 Conflict,
12 Invalid,
13 /// The workspace has to pay before this can happen.
14 PaymentRequired,
15 // Billing's refusals to start compute (`reserve`), each with a message
16 // that says what to do. See `g1t_contracts::billing::ReserveArgs`.
17 /// No plan, and no trial or pool that pays for this kind of work: a
18 /// card check or the g1t plan is needed.
19 NotPaid,
20 /// The workspace's one trial is spent.
21 TrialUsed,
22 /// The workspace reached its spend limit or g1t's ceiling.
23 Limit,
24 /// Compute is paused: a spend spike waiting for an owner, or a hold.
25 Paused,
26 /// This month's open-source pool, or the repository's share, is spent.
27 OssPoolEmpty,
28 /// A sensitive change needs the person to prove it is them again: a
29 /// recent sign-in, or their password. See `identity::Reauth`.
30 ReauthRequired,
31 /// Another host g1t depends on for this did not answer.
32 Unavailable,
33 /// What was sent is larger than this takes, such as an attachment over 10 MB.
34 TooLarge,
35 /// What was sent is not of a type this takes, such as an attachment that is not an image.
36 UnsupportedType,
37}
38
39impl FailureCode {
40 pub fn http_status(self) -> u16 {
41 match self {
42 FailureCode::NotFound => 404,
43 FailureCode::Forbidden => 403,
44 FailureCode::Unauthenticated => 401,
45 FailureCode::Conflict => 409,
46 FailureCode::Invalid => 422,
47 FailureCode::PaymentRequired
48 | FailureCode::NotPaid
49 | FailureCode::TrialUsed
50 | FailureCode::Limit
51 | FailureCode::OssPoolEmpty => 402,
52 FailureCode::Paused => 409,
53 FailureCode::ReauthRequired => 403,
54 FailureCode::Unavailable => 503,
55 FailureCode::TooLarge => 413,
56 FailureCode::UnsupportedType => 415,
57 }
58 }
59}
60
61#[derive(Clone, Debug, Serialize, Deserialize)]
62pub struct Failure {
63 pub code: FailureCode,
64 pub message: String,
65}
66
67/// The result of a service call. Expected failures cross service boundaries
68/// as values, so callers have to handle them.
69///
70/// On the wire: `{"ok": true, "value": …}` or `{"ok": false, "error": …}`.
71#[derive(Clone, Debug)]
72pub enum Outcome<T> {
73 Ok(T),
74 Fail(Failure),
75}
76
77impl<T> Outcome<T> {
78 pub fn fail(code: FailureCode, message: impl Into<String>) -> Self {
79 Outcome::Fail(Failure {
80 code,
81 message: message.into(),
82 })
83 }
84
85 pub fn into_result(self) -> Result<T, Failure> {
86 match self {
87 Outcome::Ok(value) => Ok(value),
88 Outcome::Fail(failure) => Err(failure),
89 }
90 }
91}
92
93#[derive(Serialize, Deserialize)]
94#[serde(bound(serialize = "T: Serialize", deserialize = "T: DeserializeOwned"))]
95struct Wire<T> {
96 ok: bool,
97 #[serde(default, skip_serializing_if = "Option::is_none")]
98 value: Option<T>,
99 #[serde(default, skip_serializing_if = "Option::is_none")]
100 error: Option<Failure>,
101}
102
103impl<T: Serialize> Serialize for Outcome<T> {
104 fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
105 match self {
106 Outcome::Ok(value) => Wire {
107 ok: true,
108 value: Some(value),
109 error: None,
110 },
111 Outcome::Fail(failure) => Wire {
112 ok: false,
113 value: None,
114 error: Some(failure.clone()),
115 },
116 }
117 .serialize(serializer)
118 }
119}
120
121impl<'de, T: DeserializeOwned> Deserialize<'de> for Outcome<T> {
122 fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
123 let wire = Wire::<T>::deserialize(deserializer)?;
124 match (wire.ok, wire.value, wire.error) {
125 (true, Some(value), _) => Ok(Outcome::Ok(value)),
126 (false, _, Some(error)) => Ok(Outcome::Fail(error)),
127 // `"value": null`, or no value: what `Ok(None)` and `Ok(())` are
128 // written as. `Option<Option<T>>` reads a null as the outer
129 // `None`, so the value is read from nothing instead: `None` for
130 // an `Option`, `()` for a unit, and still malformed for a type
131 // that needs a value.
132 (true, None, _) => T::deserialize(UnitDeserializer::<D::Error>::new())
133 .map(Outcome::Ok)
134 .map_err(|_| serde::de::Error::custom("malformed outcome: ok without a value")),
135 _ => Err(serde::de::Error::custom("malformed outcome")),
136 }
137 }
138}
139
140#[cfg(test)]
141mod tests {
142 use super::*;
143
144 fn round_trip<T: Serialize + DeserializeOwned>(outcome: &Outcome<T>) -> Result<Outcome<T>, String> {
145 // As a service replies (`g1t_kit::reply`) and its caller reads it
146 // (`g1t_kit::call`).
147 let wire = serde_json::to_string(outcome).map_err(|e| e.to_string())?;
148 serde_json::from_str(&wire).map_err(|e| e.to_string())
149 }
150
151 /// A cache miss is `Ok(None)`, written `{"ok":true,"value":null}`. It
152 /// was read back as malformed, so every miss of the toolkit's cache
153 /// (sccache's first lookup, `sccache/.sccache_check`) was a 500.
154 #[test]
155 fn ok_none_and_ok_unit_cross_the_wire() {
156 assert_eq!(serde_json::to_string(&Outcome::<Option<u8>>::Ok(None)).unwrap(), r#"{"ok":true,"value":null}"#);
157 assert!(matches!(round_trip(&Outcome::<Option<u8>>::Ok(None)), Ok(Outcome::Ok(None))));
158 assert!(matches!(round_trip(&Outcome::Ok(Some(7u8))), Ok(Outcome::Ok(Some(7)))));
159 assert!(matches!(round_trip(&Outcome::Ok(())), Ok(Outcome::Ok(()))));
160 assert!(matches!(serde_json::from_str::<Outcome<Option<u8>>>(r#"{"ok":true}"#), Ok(Outcome::Ok(None))));
161 let failed = round_trip(&Outcome::<Option<u8>>::fail(FailureCode::Unauthenticated, "no"));
162 assert!(matches!(failed, Ok(Outcome::Fail(Failure { code: FailureCode::Unauthenticated, .. }))));
163 }
164
165 #[test]
166 fn an_ok_without_the_value_it_needs_is_still_malformed() {
167 assert!(serde_json::from_str::<Outcome<u8>>(r#"{"ok":true,"value":null}"#).is_err());
168 assert!(serde_json::from_str::<Outcome<String>>(r#"{"ok":true}"#).is_err());
169 assert!(serde_json::from_str::<Outcome<u8>>(r#"{"ok":false}"#).is_err());
170 }
171}