Add try_setter option and generate appropriate methods

.travis.yml

@@ -10,7 +10,7 @@ matrix:
     - rust: 1.15.0
       env: JOB=build CARGO_FEATURES="struct_default"
     - rust: nightly
-      env: JOB=build CARGO_FEATURES="compiletests logging"
+      env: JOB=build CARGO_FEATURES="nightlytests logging"
     - rust: nightly
       env: JOB=style_check
   allow_failures:

derive_builder/CHANGELOG.md

@@ -2,6 +2,16 @@
 All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
+## Unreleased
+
+### Added
+- try_setters, e.g. `#[builder(try_setter)]`. These setters are exposed alongside the
+  normal field setters and allow callers to pass in values which have 
+  fallible conversions to the needed type through `TryInto`. This attribute 
+  can only be used on nightly when until `#![feature(try_from)]` is declared 
+  in the consuming crate's root; this will change when Rust issue 
+  [#33417](https://github.com/rust-lang/rust/issues/33417) is resolved.
+
 ## [0.4.3] - 2017-04-11
 
 ### Fixed

derive_builder/src/lib.rs

@@ -216,6 +216,50 @@
 //! }
 //! ```
 //!
+//! ## Fallible Setters
+//!
+//! Alongside the normal setter methods, you can expose fallible setters which are generic over
+//! the `TryInto` trait. TryInto is a not-yet-stable trait 
+//! (see rust-lang issue [#33417](https://github.com/rust-lang/rust/issues/33417)) similar to
+//! `Into` with the key distinction that the conversion can fail, and therefore produces a `Result`.
+//! 
+//! You can only declare the `try_setter` attribute today if you're targeting nightly, and you have
+//! to add `#![feature(try_from)]` to your crate to use it.
+//!
+//!
+//! ```rust,ignore
+//! #![feature(try_from)]
+//! # #[macro_use]
+//! # extern crate derive_builder;
+//! #
+//! #[derive(Builder, Debug, PartialEq)]
+//! #[builder(try_setter, setter(into))]
+//! struct Lorem {
+//!     pub name: String,
+//!     pub ipsum: u8,
+//! }
+//! 
+//! #[derive(Builder, Debug, PartialEq)]
+//! struct Ipsum {
+//!     #[builder(try_setter, setter(into, name = "foo"))]
+//!     pub dolor: u8,
+//! }
+//!
+//! fn main() {
+//!    LoremBuilder::default()
+//!        .try_ipsum(1u16).unwrap()
+//!        .name("hello")
+//!        .build()
+//!        .expect("1 fits into a u8");
+//!
+//!    IpsumBuilder::default()
+//!        .try_foo(1u16)
+//!        .unwrap()
+//!        .build()
+//!        .expect("1 fits into a u8");
+//! }
+//! ```
+//!
 //! ## Default Values
 //!
 //! You can define default values for each field via annotation by `#[builder(default="...")]`,
@@ -366,6 +410,9 @@
 //! - If derive_builder depends on your crate, and vice versa, then a cyclic
 //!   dependency would occur. To break it you could try to depend on the
 //!   [`derive_builder_core`] crate instead.
+//! - The `try_setter` attribute and `owned` builder pattern are not compatible in practice;
+//!   an error during building will consume the builder, making it impossible to continue
+//!   construction.
 //!
 //! ## Debugging Info
 //!

derive_builder/src/options/field_mode.rs

@@ -81,6 +81,7 @@ impl OptionsBuilder<FieldMode> {
             setter_vis: f!(setter_vis),
             default_expression: f!(default_expression),
             setter_into: f!(setter_into),
+            try_setter: f!(try_setter),
             no_std: f!(no_std),
             mode: mode,
         }
@@ -133,6 +134,7 @@ impl From<OptionsBuilder<FieldMode>> for FieldOptions {
             field_ident: field_ident,
             field_type: field_type,
             setter_into: b.setter_into.unwrap_or(false),
+            try_setter: b.try_setter.unwrap_or(false),
             deprecation_notes: b.mode.deprecation_notes.clone(),
             default_expression: b.default_expression.clone(),
             use_default_struct: b.mode.use_default_struct,

derive_builder/src/options/field_options.rs

@@ -31,6 +31,8 @@ pub struct FieldOptions {
     pub attrs: Vec<syn::Attribute>,
     /// Bindings to libstd or libcore.
     pub bindings: Bindings,
+    /// Enables code generation for the TryInto setter.
+    pub try_setter: bool,
 }
 
 impl DefaultExpression {
@@ -58,6 +60,7 @@ impl FieldOptions {
     pub fn as_setter<'a>(&'a self) -> Setter<'a> {
         Setter {
             enabled: self.setter_enabled,
+            try_setter: self.try_setter,
             visibility: &self.setter_visibility,
             pattern: self.builder_pattern,
             attrs: &self.attrs,

derive_builder/src/options/mod.rs

@@ -45,6 +45,7 @@ pub struct OptionsBuilder<Mode> {
     setter_vis: Option<syn::Visibility>,
     default_expression: Option<DefaultExpression>,
     setter_into: Option<bool>,
+    try_setter: Option<bool>,
     no_std: Option<bool>,
     mode: Mode,
 }
@@ -66,6 +67,7 @@ impl<Mode> From<Mode> for OptionsBuilder<Mode> {
             setter_prefix: None,
             setter_name: None,
             setter_vis: None,
+            try_setter: None,
             default_expression: None,
             setter_into: None,
             no_std: None,
@@ -100,6 +102,12 @@ impl<Mode> OptionsBuilder<Mode> where
         desc: "setter type conversion",
         map: |x: bool| { x },
     }
+
+    impl_setter!{
+        ident: try_setter,
+        desc: "try_setter activation",
+        map: |x: bool| { x },
+    }
 
     impl_setter!{
         ident: default_expression,
@@ -198,6 +206,9 @@ impl<Mode> OptionsBuilder<Mode> where
                 // setter implicitly enabled
                 self.setter_enabled(true)
             },
+            "try_setter" => {
+                self.try_setter(true)
+            }
             "default" => {
                 if !cfg!(feature = "struct_default") && self.mode.struct_mode() {
                     let where_info = self.where_diagnostics();

derive_builder/src/options/struct_mode.rs

@@ -78,6 +78,7 @@ impl From<OptionsBuilder<StructMode>> for (StructOptions, OptionsBuilder<FieldMo
             setter_prefix: b.setter_prefix,
             setter_vis: b.setter_vis,
             setter_into: b.setter_into,
+            try_setter: b.try_setter,
             default_expression: field_default_expression,
             no_std: b.no_std,
             mode: {

derive_builder_core/src/bindings.rs

@@ -70,6 +70,15 @@ impl Bindings {
             ":: std :: convert :: Into"
         })
     }
+
+    /// TryInto trait.
+    pub fn try_into_trait(&self) -> RawTokens<&'static str> {
+        RawTokens(if self.no_std {
+            ":: core :: convert :: TryInto"
+        } else {
+            ":: std :: convert :: TryInto"
+        })
+    }
 }
 
 #[test]

derive_builder_core/src/lib.rs

@@ -22,6 +22,7 @@
 //! [`derive_builder_core`]: https://!crates.io/crates/derive_builder_core
 
 #![deny(warnings, missing_docs)]
+#![cfg_attr(test, recursion_limit = "100")]
 
 extern crate proc_macro;
 extern crate syn;

derive_builder_core/src/setter.rs

@@ -34,6 +34,8 @@ use Bindings;
 pub struct Setter<'a> {
     /// Enables code generation for this setter fn.
     pub enabled: bool,
+    /// Enables code generation for the `try_` variant of this setter fn.
+    pub try_setter: bool,
     /// Visibility of the setter, e.g. `syn::Visibility::Public`.
     pub visibility: &'a syn::Visibility,
     /// How the setter method takes and returns `self` (e.g. mutably).
@@ -117,6 +119,26 @@ impl<'a> ToTokens for Setter<'a> {
                     new.#field_ident = #option::Some(#into_value);
                     new
             }));
+
+            if self.try_setter {
+                let try_into = self.bindings.try_into_trait();
+                let try_ty_params = quote!(<VALUE: #try_into<#ty>>);
+                let try_ident = syn::Ident::new(format!("try_{}", ident));
+                let result = self.bindings.result_ty();
+
+                tokens.append(quote!(
+                    #(#attrs)*
+                    #vis fn #try_ident #try_ty_params (#self_param, value: VALUE)
+                        -> #result<#return_ty, VALUE::Error>
+                    {
+                        let converted : #ty = value.try_into()?;
+                        let mut new = #self_into_return_ty;
+                        new.#field_ident = #option::Some(converted);
+                        Ok(new)
+                }));
+            } else {
+                trace!("Skipping try_setter for `{}`.", self.field_ident);
+            }
         } else {
             trace!("Skipping setter for `{}`.", self.field_ident);
         }
@@ -131,6 +153,7 @@ macro_rules! default_setter {
     () => {
         Setter {
             enabled: true,
+            try_setter: false,
             visibility: &syn::Visibility::Public,
             pattern: BuilderPattern::Mutable,
             attrs: &vec![],
@@ -221,7 +244,7 @@ mod tests {
         ));
     }
 
-    // including
+    // including try_setter
     #[test]
     fn full() {
         let attrs = vec![syn::parse_outer_attr("#[some_attr]").unwrap()];
@@ -233,6 +256,7 @@ mod tests {
         setter.attrs = attrs.as_slice();
         setter.generic_into = true;
         setter.deprecation_notes = &deprecated;
+        setter.try_setter = true;
 
         assert_eq!(quote!(#setter), quote!(
             #[some_attr]
@@ -242,6 +266,15 @@ mod tests {
                 new.foo = ::std::option::Option::Some(value.into());
                 new
             }
+
+            #[some_attr]
+            pub fn try_foo<VALUE: ::std::convert::TryInto<Foo>>(&mut self, value: VALUE) 
+                -> ::std::result::Result<&mut Self, VALUE::Error> {
+                let converted : Foo = value.try_into()?;
+                let mut new = self;
+                new.foo = ::std::option::Option::Some(converted);
+                Ok(new)
+            }
         ));
     }
 
@@ -282,4 +315,27 @@ mod tests {
 
         assert_eq!(quote!(#setter), quote!());
     }
+
+    #[test]
+    fn try_setter() {
+        let mut setter : Setter = default_setter!();
+        setter.pattern = BuilderPattern::Mutable;
+        setter.try_setter = true;
+
+        assert_eq!(quote!(#setter), quote!(
+            pub fn foo(&mut self, value: Foo) -> &mut Self {
+                let mut new = self;
+                new.foo = ::std::option::Option::Some(value);
+                new
+            }
+
+            pub fn try_foo<VALUE: ::std::convert::TryInto<Foo>>(&mut self, value: VALUE) 
+                -> ::std::result::Result<&mut Self, VALUE::Error> {
+                let converted : Foo = value.try_into()?;
+                let mut new = self;
+                new.foo = ::std::option::Option::Some(converted);
+                Ok(new)
+            }
+        ));
+    }
 }

derive_builder_test/Cargo.toml

@@ -9,7 +9,7 @@ publish = false
 path = "src/lib.rs"
 
 [features]
-compiletests = ["compiletest_rs"]
+nightlytests = ["compiletest_rs"]
 logging = [ "derive_builder/logging" ]
 struct_default = [ "derive_builder/struct_default" ]
 

derive_builder_test/tests/compiletests.rs

@@ -1,4 +1,4 @@
-#![cfg(feature = "compiletests")]
+#![cfg(feature = "nightlytests")]
 extern crate compiletest_rs as compiletest;
 
 // note: