Move json into it's own crate

Not everyone needs json, so no reason to force people to build
it.

serde_json/src/builder.rs

@@ -0,0 +1,85 @@
+// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::collections::BTreeMap;
+
+use serde::ser::{self, Serialize};
+
+use value::{self, Value};
+
+pub struct ArrayBuilder {
+    array: Vec<Value>,
+}
+
+impl ArrayBuilder {
+    pub fn new() -> ArrayBuilder {
+        ArrayBuilder { array: Vec::new() }
+    }
+
+    pub fn unwrap(self) -> Value {
+        Value::Array(self.array)
+    }
+
+    pub fn push<T: ser::Serialize>(mut self, v: T) -> ArrayBuilder {
+        self.array.push(value::to_value(&v));
+        self
+    }
+
+    pub fn push_array<F>(mut self, f: F) -> ArrayBuilder where
+        F: FnOnce(ArrayBuilder) -> ArrayBuilder
+    {
+        let builder = ArrayBuilder::new();
+        self.array.push(f(builder).unwrap());
+        self
+    }
+
+    pub fn push_object<F>(mut self, f: F) -> ArrayBuilder where
+        F: FnOnce(ObjectBuilder) -> ObjectBuilder
+    {
+        let builder = ObjectBuilder::new();
+        self.array.push(f(builder).unwrap());
+        self
+    }
+}
+
+pub struct ObjectBuilder {
+    object: BTreeMap<String, Value>,
+}
+
+impl ObjectBuilder {
+    pub fn new() -> ObjectBuilder {
+        ObjectBuilder { object: BTreeMap::new() }
+    }
+
+    pub fn unwrap(self) -> Value {
+        Value::Object(self.object)
+    }
+
+    pub fn insert<V: ser::Serialize>(mut self, k: String, v: V) -> ObjectBuilder {
+        self.object.insert(k, value::to_value(&v));
+        self
+    }
+
+    pub fn insert_array<F>(mut self, key: String, f: F) -> ObjectBuilder where
+        F: FnOnce(ArrayBuilder) -> ArrayBuilder
+    {
+        let builder = ArrayBuilder::new();
+        self.object.insert(key, f(builder).unwrap());
+        self
+    }
+
+    pub fn insert_object<F>(mut self, key: String, f: F) -> ObjectBuilder where
+        F: FnOnce(ObjectBuilder) -> ObjectBuilder
+    {
+        let builder = ObjectBuilder::new();
+        self.object.insert(key, f(builder).unwrap());
+        self
+    }
+}