Change meaning of `Option`

core/lib/src/data/from_data.rs

@@ -415,12 +415,14 @@ impl<'r, T: FromData<'r> + 'r> FromData<'r> for Result<T, T::Error> {
 
 #[crate::async_trait]
 impl<'r, T: FromData<'r>> FromData<'r> for Option<T> {
-    type Error = std::convert::Infallible;
+    type Error = T::Error;
 
-    async fn from_data(req: &'r Request<'_>, data: Data<'r>) -> Outcome<'r, Self> {
-        match T::from_data(req, data).await {
-            Success(v) => Success(Some(v)),
-            Error(..) | Forward(..) => Success(None),
+    async fn from_data(req: &'r Request<'_>, mut data: Data<'r>) -> Outcome<'r, Self> {
+        // Ask for at least one byte of data, if it's empty, there is no body.
+        if data.peek(1).await.is_empty() {
+            Outcome::Success(None)
+        } else {
+            T::from_data(req, data).await.map(Some)
         }  
     }
 }

core/lib/src/form/from_form.rs

@@ -814,24 +814,51 @@ impl<'v, K, V> FromForm<'v> for BTreeMap<K, V>
     }
 }
 
+struct OptionFormCtx<'v, T: FromForm<'v>> {
+    strict: bool,
+    has_field: bool,
+    inner: T::Context,
+}
+
 #[crate::async_trait]
 impl<'v, T: FromForm<'v>> FromForm<'v> for Option<T> {
-    type Context = <T as FromForm<'v>>::Context;
+    type Context = OptionFormCtx<'v, T>;
 
-    fn init(_: Options) -> Self::Context {
-        T::init(Options { strict: true })
+    fn init(opts: Options) -> Self::Context {
+        OptionFormCtx {
+            strict: opts.strict,
+            has_field: false,
+            inner: T::init(Options { strict: true }),
+        }
     }
 
     fn push_value(ctxt: &mut Self::Context, field: ValueField<'v>) {
-        T::push_value(ctxt, field)
+        ctxt.has_field = true;
+        T::push_value(&mut ctxt.inner, field)
     }
 
     async fn push_data(ctxt: &mut Self::Context, field: DataField<'v, '_>) {
-        T::push_data(ctxt, field).await
+        ctxt.has_field = true;
+        T::push_data(&mut ctxt.inner, field).await
     }
 
     fn finalize(this: Self::Context) -> Result<'v, Self> {
-        Ok(T::finalize(this).ok())
+        if this.has_field {
+            match T::finalize(this.inner) {
+                Ok(v) => Ok(Some(v)),
+                Err(errors) => {
+                    if this.strict ||
+                        errors.iter().any(|e| e.kind != ErrorKind::Missing)
+                    {
+                        Err(errors)
+                    } else {
+                        Ok(None)
+                    }
+                }
+            }
+        } else {
+            Ok(None)
+        }
     }
 }
 

core/lib/src/request/from_param.rs

@@ -299,17 +299,17 @@ impl<'a, T: FromParam<'a>> FromParam<'a> for Result<T, T::Error> {
     }
 }
 
-impl<'a, T: FromParam<'a>> FromParam<'a> for Option<T> {
-    type Error = std::convert::Infallible;
+// impl<'a, T: FromParam<'a>> FromParam<'a> for Option<T> {
+//     type Error = std::convert::Infallible;
 
-    #[inline]
-    fn from_param(param: &'a str) -> Result<Self, Self::Error> {
-        match T::from_param(param) {
-            Ok(val) => Ok(Some(val)),
-            Err(_) => Ok(None)
-        }
-    }
-}
+//     #[inline]
+//     fn from_param(param: &'a str) -> Result<Self, Self::Error> {
+//         match T::from_param(param) {
+//             Ok(val) => Ok(Some(val)),
+//             Err(_) => Ok(None)
+//         }
+//     }
+// }
 
 /// Trait to convert _many_ dynamic path segment strings to a concrete value.
 ///
@@ -384,13 +384,14 @@ impl<'r, T: FromSegments<'r>> FromSegments<'r> for Result<T, T::Error> {
 }
 
 impl<'r, T: FromSegments<'r>> FromSegments<'r> for Option<T> {
-    type Error = std::convert::Infallible;
+    type Error = T::Error;
 
     #[inline]
     fn from_segments(segments: Segments<'r, Path>) -> Result<Option<T>, Self::Error> {
-        match T::from_segments(segments) {
-            Ok(val) => Ok(Some(val)),
-            Err(_) => Ok(None)
+        if segments.is_empty() {
+            Ok(None)
+        } else {
+            T::from_segments(segments).map(Some)
         }
     }
 }