Support chrono-tz::Tz GraphQL scalar (#519)

Co-authored-by: Nirman Gupta <nirmangupta@gmail.com>
Co-authored-by: Kai Ren <tyranron@gmail.com>

README.md

@@ -68,6 +68,7 @@ your Schemas automatically.
 - [uuid][uuid]
 - [url][url]
 - [chrono][chrono]
+- [chrono-tz][chrono-tz]
 - [bson][bson]
 
 ### Web Frameworks
@@ -112,5 +113,6 @@ Juniper has not reached 1.0 yet, thus some API instability should be expected.
 [uuid]: https://crates.io/crates/uuid
 [url]: https://crates.io/crates/url
 [chrono]: https://crates.io/crates/chrono
+[chrono-tz]: https://crates.io/crates/chrono-tz
 [bson]: https://crates.io/crates/bson
 [juniper-from-schema]: https://github.com/davidpdrsn/juniper-from-schema

juniper/CHANGELOG.md

@@ -33,6 +33,8 @@
   - `ParseError`
   - `RuleError`
   
+- Support `chrono-tz::Tz` scalar behind a `chrono-tz` feature flag. ([#519](https://github.com/graphql-rust/juniper/pull/519))
+  
 ## Fixes
 
 - Massively improved the `#[graphql_union]` proc macro. ([#666](https://github.com/graphql-rust/juniper/pull/666)):

juniper/Cargo.toml

@@ -38,6 +38,7 @@ anyhow = { default-features = false, version = "1.0.32", optional = true }
 async-trait = "0.1.39"
 bson = { version = "1.0", optional = true }
 chrono = { default-features = false, version = "0.4", optional = true }
+chrono-tz = { version = "0.5", default-features = false, optional = true }
 fnv = "1.0.3"
 futures = { default-features = false, features = ["alloc"], version = "0.3.1" }
 futures-enum = "0.1.12"

juniper/src/integrations/chrono_tz.rs

@@ -0,0 +1,80 @@
+//! [`Tz`] (timezone) scalar implementation, represented by its [IANA database][1] name.
+//!
+//! [`Tz`]: chrono_tz::Tz
+//! [1]: http://www.iana.org/time-zones
+
+use chrono_tz::Tz;
+
+use crate::{
+    graphql_scalar,
+    parser::{ParseError, ScalarToken, Token},
+    value::ParseScalarResult,
+    Value,
+};
+
+#[graphql_scalar(name = "Tz", description = "Timezone")]
+impl<S> GraphQLScalar for Tz
+where
+    S: ScalarValue,
+{
+    fn resolve(&self) -> Value {
+        Value::scalar(self.name().to_owned())
+    }
+
+    fn from_input_value(v: &InputValue) -> Option<Tz> {
+        v.as_string_value().and_then(|s| s.parse::<Tz>().ok())
+    }
+
+    fn from_str<'a>(val: ScalarToken<'a>) -> ParseScalarResult<'a, S> {
+        if let ScalarToken::String(s) = val {
+            Ok(S::from(s.to_owned()))
+        } else {
+            Err(ParseError::UnexpectedToken(Token::Scalar(val)))
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    mod from_input_value {
+        use chrono_tz::Tz;
+
+        use crate::{DefaultScalarValue, FromInputValue, InputValue};
+
+        fn tz_input_test(raw: &'static str, expected: Option<Tz>) {
+            let input = <InputValue<DefaultScalarValue>>::scalar(raw.to_string());
+            let parsed: Option<Tz> = FromInputValue::from_input_value(&input);
+
+            assert_eq!(parsed, expected);
+        }
+
+        #[test]
+        fn europe_zone() {
+            tz_input_test("Europe/London", Some(chrono_tz::Europe::London));
+        }
+
+        #[test]
+        fn etc_minus() {
+            tz_input_test("Etc/GMT-3", Some(chrono_tz::Etc::GMTMinus3));
+        }
+
+        mod invalid {
+            use super::tz_input_test;
+
+            #[test]
+            fn forward_slash() {
+                tz_input_test("Abc/Xyz", None);
+            }
+
+            #[test]
+            fn number() {
+                tz_input_test("8086", None);
+            }
+
+            #[test]
+            fn no_forward_slash() {
+                tz_input_test("AbcXyz", None);
+            }
+        }
+    }
+}

juniper/src/integrations/mod.rs

@@ -7,6 +7,10 @@ pub mod serde;
 /// GraphQL support for [chrono](https://github.com/chronotope/chrono) types.
 pub mod chrono;
 
+#[cfg(feature = "chrono-tz")]
+/// GraphQL support for [chrono-tz](https://github.com/chronotope/chrono-tz) types.
+pub mod chrono_tz;
+
 #[cfg(feature = "url")]
 /// GraphQL support for [url](https://github.com/servo/rust-url) types.
 pub mod url;

juniper_codegen/src/util/mod.rs

@@ -4,8 +4,7 @@ pub mod duplicate;
 pub mod parse_impl;
 pub mod span_container;
 
-use std::collections::HashMap;
+use std::{collections::HashMap, str::FromStr};
-use std::str::FromStr;
 
 use proc_macro2::{Span, TokenStream};
 use proc_macro_error::abort;