Generate schema from any serializable value (#75)

Implement schema_for_value!(...) macro

docs/3-generating.md

@@ -20,6 +20,8 @@ If you want more control over how the schema is generated, you can use the [`gen
 
 See the API documentation for more info on how to use those types for custom schema generation.
 
-<!-- TODO: 
+<!-- TODO:
 create and link to example
+
+Generating schema from example value
 -->

docs/_includes/examples/from_value.rs

@@ -0,0 +1,24 @@
+use schemars::schema_for_value;
+use serde::Serialize;
+
+#[derive(Serialize)]
+pub struct MyStruct {
+    pub my_int: i32,
+    pub my_bool: bool,
+    pub my_nullable_enum: Option<MyEnum>,
+}
+
+#[derive(Serialize)]
+pub enum MyEnum {
+    StringNewType(String),
+    StructVariant { floats: Vec<f32> },
+}
+
+fn main() {
+    let schema = schema_for_value!(MyStruct {
+        my_int: 123,
+        my_bool: true,
+        my_nullable_enum: Some(MyEnum::StringNewType("foo".to_string()))
+    });
+    println!("{}", serde_json::to_string_pretty(&schema).unwrap());
+}

docs/_includes/examples/from_value.schema.json

@@ -0,0 +1,24 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "title": "MyStruct",
+  "examples": [
+    {
+      "my_bool": true,
+      "my_int": 123,
+      "my_nullable_enum": {
+        "StringNewType": "foo"
+      }
+    }
+  ],
+  "type": "object",
+  "properties": {
+    "my_bool": {
+      "type": "boolean"
+    },
+    "my_int": {
+      "type": "integer",
+      "format": "int32"
+    },
+    "my_nullable_enum": true
+  }
+}