Implemented FromForm derivation. Woo!

examples/forms/src/main.rs

@@ -1,4 +1,4 @@
-#![feature(plugin)]
+#![feature(plugin, custom_derive)]
 #![plugin(rocket_macros)]
 
 extern crate rocket;
@@ -7,65 +7,19 @@ mod files;
 
 use rocket::Rocket;
 use rocket::response::Redirect;
-use rocket::Error;
-use rocket::form::{FromForm, FromFormValue, form_items};
 
 #[route(GET, path = "/user/<username>")]
 fn user_page(username: &str) -> String {
     format!("This is {}'s page.", username)
 }
 
-// #[derive(FromForm)] // FIXME: Make that happen.
+#[derive(FromForm)]
-struct UserLogin<'a> {
+struct UserLogin<'r> {
-    username: &'a str,
+    username: &'r str,
-    password: &'a str,
+    password: &'r str,
-    age: Result<isize, &'a str>,
+    age: Result<isize, &'r str>,
 }
 
-// will help for validation. IE, can have a type Range(1, 10) that returns an
-// enum with one of: TooLow(isize), TooHigh(isize), etc.
-impl<'f> FromForm<'f> for UserLogin<'f> {
-    fn from_form_string(s: &'f str) -> Result<Self, Error> {
-        let mut items = [("", ""); 3];
-        let form_count = form_items(s, &mut items);
-        if form_count != items.len() {
-            return Err(Error::BadParse);
-        }
-
-        let mut username: Option<&'f str> = None;
-        let mut password: Option<&'f str> = None;
-        let mut age: Option<Result<isize, &'f str>> = None;
-        for &(key, value) in &items {
-            match key {
-                "username" => username = match FromFormValue::parse(value) {
-                    Ok(v) => Some(v),
-                    Err(_) => return Err(Error::BadParse)
-                },
-                "password" => password = match FromFormValue::parse(value) {
-                    Ok(v) => Some(v),
-                    Err(_) => return Err(Error::BadParse)
-                },
-                "age" => age = match FromFormValue::parse(value) {
-                    Ok(v) => Some(v),
-                    Err(_) => return Err(Error::BadParse)
-                },
-                _ => return Err(Error::BadParse)
-            }
-        }
-
-        if username.is_none() || password.is_none() {
-            return Err(Error::BadParse);
-        }
-
-        Ok(UserLogin {
-            username: username.unwrap(),
-            password: password.unwrap(),
-            age: age.unwrap(),
-        })
-    }
-}
-
-// TODO: Actually look at form parameters.
 // FIXME: fn login<'a>(user: UserLogin<'a>)
 #[route(POST, path = "/login", form = "<user>")]
 fn login(user: UserLogin) -> Result<Redirect, String> {

macros/src/derive_form.rs

@@ -0,0 +1,207 @@
+#![allow(unused_imports)] // FIXME: Why is this coming from quote_tokens?
+
+use syntax::ext::base::{Annotatable, ExtCtxt};
+use syntax::ast::{ItemKind, Expr, MetaItem, Mutability, VariantData};
+use syntax::codemap::Span;
+use syntax::ext::build::AstBuilder;
+use syntax::ptr::P;
+use std::mem::transmute;
+
+use syntax_ext::deriving::generic::MethodDef;
+use syntax_ext::deriving::generic::{StaticStruct, Substructure, TraitDef, ty};
+use syntax_ext::deriving::generic::combine_substructure as c_s;
+
+const DEBUG: bool = false;
+
+static ONLY_STRUCTS_ERR: &'static str = "`FromForm` can only be derived for \
+    structures with named fields.";
+
+fn get_struct_lifetime(ecx: &mut ExtCtxt, item: &Annotatable, span: Span)
+        -> Option<&'static str> {
+    match item {
+        &Annotatable::Item(ref item) => match item.node {
+            ItemKind::Struct(_, ref generics) => {
+                match generics.lifetimes.len() {
+                    0 => None,
+                    1 => {
+                        let lifetime = generics.lifetimes[0].lifetime;
+                        // According to the documentation, this is safe:
+                        //  Because the interner lives for the life of the
+                        //  thread, this can be safely treated as an immortal
+                        //  string, as long as it never crosses between threads.
+                        let lifetime_name: &'static str =
+                            unsafe { transmute(&*lifetime.name.as_str()) };
+                        Some(lifetime_name)
+                    }
+                    _ => {
+                        ecx.span_err(item.span, "cannot have more than one \
+                            lifetime parameter when deriving `FromForm`.");
+                        None
+                    }
+                }
+            },
+            _ => ecx.span_fatal(span, ONLY_STRUCTS_ERR)
+        },
+        _ => ecx.span_fatal(span, ONLY_STRUCTS_ERR)
+    }
+}
+
+pub fn from_form_derive(ecx: &mut ExtCtxt, span: Span, meta_item: &MetaItem,
+          annotated: &Annotatable, push: &mut FnMut(Annotatable)) {
+    let lifetime_var = get_struct_lifetime(ecx, annotated, span);
+
+    let trait_def = TraitDef {
+        is_unsafe: false,
+        span: span,
+        attributes: Vec::new(),
+        path: ty::Path {
+            path: vec!["rocket", "form", "FromForm"],
+            lifetime: lifetime_var,
+            params: vec![],
+            global: true,
+        },
+        additional_bounds: Vec::new(),
+        generics: ty::LifetimeBounds::empty(),
+        methods: vec![
+            MethodDef {
+                name: "from_form_string",
+                generics: ty::LifetimeBounds::empty(),
+                explicit_self: None,
+                args: vec![
+                    ty::Ptr(
+                        Box::new(ty::Literal(ty::Path::new_local("str"))),
+                        ty::Borrowed(lifetime_var, Mutability::Immutable)
+                    )
+                ],
+                ret_ty: ty::Ty::Literal(
+                    ty::Path {
+                        path: vec!["std", "result", "Result"],
+                        lifetime: None,
+                        params: vec![
+                            Box::new(ty::Ty::Self_),
+                            Box::new(ty::Ty::Literal(
+                                ty::Path::new(vec!["rocket", "Error"])
+                            )),
+                        ],
+                        global: true,
+                    }
+                ),
+                attributes: vec![],
+                is_unsafe: false,
+                combine_substructure: c_s(Box::new(from_form_substructure)),
+            }
+        ],
+        associated_types: vec![],
+    };
+
+    trait_def.expand(ecx, meta_item, annotated, push);
+}
+
+// Mostly copied from syntax::ext::deriving::hash
+/// Defines how the implementation for `trace()` is to be generated
+fn from_form_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> P<Expr> {
+    let arg = if substr.nonself_args.len() == 1 {
+        &substr.nonself_args[0]
+    } else {
+        let msg = format!("incorrect number of arguments in `from_form_string`: \
+            expected {}, found {}", 1, substr.nonself_args.len());
+        cx.span_bug(trait_span, msg.as_str());
+    };
+
+    debug!("argument is: {:?}", arg);
+
+    let fields = match substr.fields {
+        &StaticStruct(var_data, _) => match var_data {
+            &VariantData::Struct(ref fields, _) => fields,
+            _ => cx.span_fatal(trait_span, ONLY_STRUCTS_ERR)
+        },
+        _ => cx.span_bug(trait_span, "impossible substructure in `from_form`")
+    };
+
+    let mut fields_and_types = vec![];
+    for field in fields {
+        let ident = match field.node.ident() {
+            Some(ident) => ident,
+            None => cx.span_fatal(trait_span, ONLY_STRUCTS_ERR)
+        };
+
+        fields_and_types.push((ident, &field.node.ty));
+    }
+
+    debug!("Fields and types: {:?}", fields_and_types);
+    let mut stmts = Vec::new();
+
+    let return_err_stmt = quote_tokens!(cx,
+        return Err(::rocket::Error::BadParse)
+    );
+
+    let num_fields = fields_and_types.len();
+    let initial_block = quote_block!(cx, {
+        let mut items = [("", ""); $num_fields];
+        let form_count = ::rocket::form::form_items($arg, &mut items);
+        if form_count != items.len() {
+            $return_err_stmt;
+        };
+    });
+
+    stmts.extend(initial_block.unwrap().stmts);
+
+    for &(ref ident, ref ty) in &fields_and_types {
+        stmts.push(quote_stmt!(cx,
+            let mut $ident: ::std::option::Option<$ty> = None;
+        ).unwrap());
+    }
+
+    let mut arms = vec![];
+    for &(ref ident, _) in &fields_and_types {
+        let ident_string = ident.to_string();
+        let id_str = ident_string.as_str();
+        arms.push(quote_tokens!(cx,
+            $id_str => $ident = match ::rocket::form::FromFormValue::parse(v) {
+                Ok(v) => Some(v),
+                Err(_) => $return_err_stmt
+            },
+        ));
+    }
+
+    stmts.push(quote_stmt!(cx,
+       for &(k, v) in &items {
+           match k {
+               $arms
+                _ => $return_err_stmt
+           };
+       }
+    ).unwrap());
+
+    let mut failure_conditions = vec![];
+    for (i, &(ref ident, _)) in (&fields_and_types).iter().enumerate() {
+        if i > 0 {
+            failure_conditions.push(quote_tokens!(cx, || $ident.is_none()));
+        } else {
+            failure_conditions.push(quote_tokens!(cx, $ident.is_none()));
+        }
+    }
+
+    let mut result_fields = vec![];
+    for &(ref ident, _) in &fields_and_types {
+        result_fields.push(quote_tokens!(cx,
+            $ident: $ident.unwrap(),
+        ));
+    }
+
+    let self_ident = substr.type_ident;
+    let final_block = quote_block!(cx, {
+        if $failure_conditions {
+            $return_err_stmt;
+        }
+
+        return Ok($self_ident {
+            $result_fields
+        });
+    });
+
+    stmts.extend(final_block.unwrap().stmts);
+    cx.expr_block(cx.block(trait_span, stmts, None))
+    // cx.expr_block(P(initial_block.unwrap()))
+}
+

macros/src/lib.rs

@@ -2,6 +2,7 @@
 #![feature(quote, concat_idents, plugin_registrar, rustc_private)]
 
 #[macro_use] extern crate syntax;
+extern crate syntax_ext;
 extern crate rustc;
 extern crate rustc_plugin;
 extern crate rocket;
@@ -9,6 +10,7 @@ extern crate rocket;
 #[macro_use] mod utils;
 mod routes_macro;
 mod route_decorator;
+mod derive_form;
 
 use rustc_plugin::Registry;
 use syntax::ext::base::SyntaxExtension;
@@ -16,6 +18,7 @@ use syntax::parse::token::intern;
 
 use routes_macro::routes_macro;
 use route_decorator::route_decorator;
+use derive_form::from_form_derive;
 
 const STRUCT_PREFIX: &'static str = "static_rocket_route_info_for_";
 const FN_PREFIX: &'static str = "rocket_route_fn_";
@@ -24,5 +27,7 @@ const FN_PREFIX: &'static str = "rocket_route_fn_";
 pub fn plugin_registrar(reg: &mut Registry) {
     reg.register_syntax_extension(intern("route"),
         SyntaxExtension::MultiDecorator(Box::new(route_decorator)));
+    reg.register_syntax_extension(intern("derive_FromForm"),
+        SyntaxExtension::MultiDecorator(Box::new(from_form_derive)));
     reg.register_macro("routes", routes_macro);
 }

macros/src/route_decorator.rs

@@ -313,10 +313,10 @@ fn get_form_stmt(ecx: &ExtCtxt, fn_args: &mut Vec<SimpleArg>,
         let $param_ident: $param_ty = {
             let form_string = std::str::from_utf8(_req.data);
             if form_string.is_err() {
-                return rocket::Response::not_found()
+                return ::rocket::Response::not_found()
             };
 
-            match FromForm::from_form_string(form_string.unwrap()) {
+            match ::rocket::form::FromForm::from_form_string(form_string.unwrap()) {
                 Ok(v) => v,
                 Err(_) => {
                     println!("\t=> Form failed to parse.");