Add Dhall support

Cargo.toml

@@ -15,12 +15,13 @@ edition = "2018"
 maintenance = { status = "actively-developed" }
 
 [features]
-default = ["toml", "json", "yaml", "hjson", "ini", "ron", "json5"]
+default = ["toml", "json", "yaml", "hjson", "ini", "ron", "json5", "dhall"]
 json = ["serde_json"]
 yaml = ["yaml-rust"]
 hjson = ["serde-hjson"]
 ini = ["rust-ini"]
 json5 = ["json5_rs"]
+dhall = ["serde_dhall"]
 preserve_order = ["indexmap", "toml/preserve_order", "serde_json/preserve_order", "ron/indexmap"]
 
 [dependencies]
@@ -37,6 +38,7 @@ rust-ini = { version = "0.17", optional = true }
 ron = { version = "0.6", optional = true }
 json5_rs = { version = "0.3", optional = true, package = "json5" }
 indexmap = { version = "1.7.0", features = ["serde-1"], optional = true}
+serde_dhall = { version = "0.10", optional = true }
 
 [dev-dependencies]
 serde_derive = "1.0.8"

src/file/format/dhall.rs

@@ -0,0 +1,55 @@
+use crate::map::Map;
+use std::error::Error;
+
+use crate::{
+    error::Unexpected,
+    value::{Value, ValueKind},
+    ConfigError,
+};
+
+pub fn parse(
+    uri: Option<&String>,
+    text: &str,
+) -> Result<Map<String, Value>, Box<dyn Error + Send + Sync>> {
+    let value = from_dhall_value(uri, serde_dhall::from_str(text).parse()?);
+    match value.kind {
+        ValueKind::Table(map) => Ok(map),
+        ValueKind::Nil => Err(Unexpected::Unit),
+        ValueKind::Boolean(value) => Err(Unexpected::Bool(value)),
+        ValueKind::Integer(value) => Err(Unexpected::Integer(value)),
+        ValueKind::Float(value) => Err(Unexpected::Float(value)),
+        ValueKind::String(value) => Err(Unexpected::Str(value)),
+        ValueKind::Array(value) => Err(Unexpected::Seq),
+    }
+    .map_err(|err| ConfigError::invalid_root(uri, err))
+    .map_err(|err| Box::new(err) as Box<dyn Error + Send + Sync>)
+}
+
+fn from_dhall_value(uri: Option<&String>, value: serde_dhall::SimpleValue) -> Value {
+    match value {
+        serde_dhall::SimpleValue::Num(num) => match num {
+            serde_dhall::NumKind::Bool(b) => Value::new(uri, ValueKind::Boolean(b)),
+            serde_dhall::NumKind::Natural(n) => Value::new(uri, ValueKind::Integer(n as i64)),
+            serde_dhall::NumKind::Integer(i) => Value::new(uri, ValueKind::Integer(i)),
+            serde_dhall::NumKind::Double(d) => Value::new(uri, ValueKind::Float(f64::from(d))),
+        },
+        serde_dhall::SimpleValue::Text(string) => Value::new(uri, ValueKind::String(string)),
+        serde_dhall::SimpleValue::List(list) => Value::new(
+            uri,
+            ValueKind::Array(list.into_iter().map(|v| from_dhall_value(uri, v)).collect()),
+        ),
+        serde_dhall::SimpleValue::Record(rec) => Value::new(
+            uri,
+            ValueKind::Table(
+                rec.into_iter()
+                    .map(|(k, v)| (k, from_dhall_value(uri, v)))
+                    .collect(),
+            ),
+        ),
+        serde_dhall::SimpleValue::Optional(Some(value))
+        | serde_dhall::SimpleValue::Union(_, Some(value)) => from_dhall_value(uri, *value),
+        serde_dhall::SimpleValue::Optional(None) | serde_dhall::SimpleValue::Union(_, None) => {
+            Value::new(uri, ValueKind::Nil)
+        }
+    }
+}

src/file/format/mod.rs

@@ -29,6 +29,9 @@ mod ron;
 #[cfg(feature = "json5")]
 mod json5;
 
+#[cfg(feature = "dhall")]
+mod dhall;
+
 #[derive(Debug, Clone, Copy, Eq, PartialEq, Hash)]
 pub enum FileFormat {
     /// TOML (parsed with toml)
@@ -58,6 +61,10 @@ pub enum FileFormat {
     /// JSON5 (parsed with json5)
     #[cfg(feature = "json5")]
     Json5,
+
+    /// Dhall (parsed with serde_dhall)
+    #[cfg(feature = "dhall")]
+    Dhall,
 }
 
 lazy_static! {
@@ -87,6 +94,9 @@ lazy_static! {
         #[cfg(feature = "json5")]
         formats.insert(FileFormat::Json5, vec!["json5"]);
 
+        #[cfg(feature = "dhall")]
+        formats.insert(FileFormat::Dhall, vec!["dhall"]);
+
         formats
     };
 }
@@ -130,6 +140,9 @@ impl FileFormat {
 
             #[cfg(feature = "json5")]
             FileFormat::Json5 => json5::parse(uri, text),
+
+            #[cfg(feature = "dhall")]
+            FileFormat::Dhall => dhall::parse(uri, text),
         }
     }
 }

tests/Settings.dhall

@@ -0,0 +1,15 @@
+{
+  debug = True
+, debug_json = True
+, production = False
+, arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+, place = {
+    name = "Torre di Pisa"
+,   longitude = 43.7224985
+,   latitude = 10.3970522
+,   favorite = False
+,   reviews = 3866
+,   rating = 4.5
+,   creator.name = "John Smith"
+  }
+}

tests/file_dhall.rs

@@ -0,0 +1,86 @@
+#![cfg(feature = "dhall")]
+
+extern crate config;
+extern crate float_cmp;
+extern crate serde;
+
+#[macro_use]
+extern crate serde_derive;
+
+use std::collections::HashMap;
+
+use config::*;
+use float_cmp::ApproxEqUlps;
+
+#[derive(Debug, Deserialize)]
+struct Place {
+    name: String,
+    longitude: f64,
+    latitude: f64,
+    favorite: bool,
+    telephone: Option<String>,
+    reviews: u64,
+    creator: HashMap<String, Value>,
+    rating: Option<f32>,
+}
+
+#[derive(Debug, Deserialize)]
+struct Settings {
+    debug: f64,
+    production: Option<String>,
+    place: Place,
+    #[serde(rename = "arr")]
+    elements: Vec<String>,
+}
+
+fn make() -> Config {
+    Config::builder()
+        .add_source(File::new("tests/Settings", FileFormat::Dhall))
+        .build()
+        .unwrap()
+}
+
+#[test]
+fn test_file() {
+    let c = make();
+
+    // Deserialize the entire file as single struct
+    let s: Settings = c.try_into().unwrap();
+
+    assert!(s.debug.approx_eq_ulps(&1.0, 2));
+    assert_eq!(s.production, Some("false".to_string()));
+    assert_eq!(s.place.name, "Torre di Pisa");
+    assert!(s.place.longitude.approx_eq_ulps(&43.7224985, 2));
+    assert!(s.place.latitude.approx_eq_ulps(&10.3970522, 2));
+    assert_eq!(s.place.favorite, false);
+    assert_eq!(s.place.reviews, 3866);
+    assert_eq!(s.place.rating, Some(4.5));
+    assert_eq!(s.place.telephone, None);
+    assert_eq!(s.elements.len(), 10);
+    assert_eq!(s.elements[3], "4".to_string());
+    assert_eq!(
+        s.place.creator["name"].clone().into_string().unwrap(),
+        "John Smith".to_string()
+    );
+}
+
+#[test]
+fn test_dhall_vec() {
+    let c = Config::builder()
+        .add_source(File::from_str(
+            r#"
+            {
+              WASTE = ["example_dir1", "example_dir2"]
+            }
+            "#,
+            FileFormat::Dhall,
+        ))
+        .build()
+        .unwrap();
+
+    let v = c.get_array("WASTE").unwrap();
+    let mut vi = v.into_iter();
+    assert_eq!(vi.next().unwrap().into_string().unwrap(), "example_dir1");
+    assert_eq!(vi.next().unwrap().into_string().unwrap(), "example_dir2");
+    assert!(vi.next().is_none());
+}