doc & ui-test for FromBody

gotham_restful/Cargo.toml

@@ -39,6 +39,7 @@ uuid = { version = "0.8.1", optional = true }
 diesel = { version = "1.4.4", features = ["postgres"] }
 futures-executor = "0.3.4"
 paste = "0.1.12"
+trybuild = "1.0.26"
 
 [features]
 default = ["errorlog"]

gotham_restful/src/types.rs

@@ -43,13 +43,36 @@ impl<T : ResourceType + Serialize> ResponseBody for T
 }
 
 
-/// This trait must be implemented by every type that can be used as a request body. It allows
-/// to create the type from a hyper body chunk and it's content type.
+/**
+This trait should be implemented for every type that can be built from an HTTP request body
+plus its media type. For most use cases it is sufficient to derive this trait, you usually
+don't need to manually implement this. Therefore, make sure that the first variable of
+your struct can be built from [`Bytes`], and the second one can be build from [`Mime`].
+If you have any additional variables, they need to be `Default`. This is an example of
+such a struct:
+
+```rust
+# #[macro_use] extern crate gotham_restful;
+# use gotham_restful::*;
+#[derive(FromBody, RequestBody)]
+#[supported_types(mime::IMAGE_GIF, mime::IMAGE_JPEG, mime::IMAGE_PNG)]
+struct RawImage {
+	content: Vec<u8>,
+	content_type: Mime
+}
+```
+
+ [`Bytes`]: ../bytes/struct.Bytes.html
+ [`Mime`]: ../mime/struct.Mime.html
+*/
 pub trait FromBody : Sized
 {
+	/// The error type returned by the conversion if it was unsuccessfull. When using the derive
+	/// macro, there is no way to trigger an error, so
+	/// [`FromBodyNoError`](struct.FromBodyNoError.html) is used here.
 	type Err : Error;
 	
-	/// Create the request body from a raw body and the content type.
+	/// Perform the conversion.
 	fn from_body(body : Bytes, content_type : Mime) -> Result<Self, Self::Err>;
 }
 
@@ -63,9 +86,8 @@ impl<T : DeserializeOwned> FromBody for T
 	}
 }
 
-/// This error type can be used by `FromBody` implementations when there is no need to return any
-/// errors.
-
+/// This error type can be used by [`FromBody`](trait.FromBody.html) implementations when there
+/// is no need to return any errors.
 #[derive(Clone, Copy, Debug, Error)]
 #[error("No Error")]
 pub struct FromBodyNoError;

gotham_restful/tests/ui.rs

@@ -0,0 +1,10 @@
+use trybuild::TestCases;
+
+#[test]
+fn ui()
+{
+	let t = TestCases::new();
+	
+	// always enabled
+	t.compile_fail("tests/ui/from_body_enum.rs");
+}

gotham_restful/tests/ui/from_body_enum.rs

@@ -0,0 +1,12 @@
+#[macro_use] extern crate gotham_restful;
+
+#[derive(FromBody)]
+enum FromBodyEnum
+{
+	SomeVariant(Vec<u8>),
+	OtherVariant(String)
+}
+
+fn main()
+{
+}

gotham_restful/tests/ui/from_body_enum.stderr

@@ -0,0 +1,5 @@
+error: #[derive(FromBody)] only works for structs
+ --> $DIR/from_body_enum.rs:4:1
+  |
+4 | enum FromBodyEnum
+  | ^^^^

gotham_restful_derive/src/from_body.rs

@@ -21,25 +21,25 @@ struct ParsedFields
 
 impl ParsedFields
 {
-	fn from_named<I>(fields : I) -> Result<Self>
+	fn from_named<I>(fields : I) -> Self
 	where
 		I : Iterator<Item = Field>
 	{
 		let fields = fields.map(|field| (field.ident.unwrap(), field.ty)).collect();
-		Ok(Self { fields, named: true })
+		Self { fields, named: true }
 	}
 	
-	fn from_unnamed<I>(fields : I) -> Result<Self>
+	fn from_unnamed<I>(fields : I) -> Self
 	where
 		I : Iterator<Item = Field>
 	{
 		let fields = fields.enumerate().map(|(i, field)| (format_ident!("arg{}", i), field.ty)).collect();
-		Ok(Self { fields, named: false })
+		Self { fields, named: false }
 	}
 	
-	fn from_unit() -> Result<Self>
+	fn from_unit() -> Self
 	{
-		Ok(Self { fields: Vec::new(), named: false })
+		Self { fields: Vec::new(), named: false }
 	}
 }
 
@@ -53,12 +53,12 @@ pub fn expand_from_body(input : DeriveInput) -> Result<TokenStream>
 		Data::Enum(inum) => Err(inum.enum_token.span()),
 		Data::Struct(strukt) => Ok(strukt),
 		Data::Union(uni) => Err(uni.union_token.span())
-	}.map_err(|span| Error::new(span, "#[derive(FromBody)] only works for enums"))?;
+	}.map_err(|span| Error::new(span, "#[derive(FromBody)] only works for structs"))?;
 	
 	let fields = match strukt.fields {
-		Fields::Named(named) => ParsedFields::from_named(named.named.into_iter())?,
-		Fields::Unnamed(unnamed) => ParsedFields::from_unnamed(unnamed.unnamed.into_iter())?,
-		Fields::Unit => ParsedFields::from_unit()?
+		Fields::Named(named) => ParsedFields::from_named(named.named.into_iter()),
+		Fields::Unnamed(unnamed) => ParsedFields::from_unnamed(unnamed.unnamed.into_iter()),
+		Fields::Unit => ParsedFields::from_unit()
 	};
 	
 	let mut where_clause = quote!();