Implement JsonSchema on smallvec + arrayvec types

Documentation still needs updating.

schemars/Cargo.toml

@@ -21,6 +21,10 @@ chrono = { version = "0.4", default-features = false, optional = true }
 indexmap = { version = "1.2", optional = true }
 either = { version = "1.3", default-features = false, optional = true }
 uuid = { version = "0.8", default-features = false, optional = true }
+smallvec = { version = "1.0", optional = true }
+arrayvec = { version = "0.5", default-features = false, optional = true }
+# TODO implement JsonSchema on bytes types. bytes 0.5 requires Rust 1.39+
+# bytes = { version = "0.5", default-features = false, optional = true }
 
 [dev-dependencies]
 pretty_assertions = "0.6.1"
@@ -46,6 +50,14 @@ required-features = ["either"]
 name = "uuid"
 required-features = ["uuid"]
 
+[[test]]
+name = "smallvec"
+required-features = ["smallvec"]
+
+[[test]]
+name = "arrayvec"
+required-features = ["arrayvec"]
+
 [[test]]
 name = "schema_for_schema"
 required-features = ["impl_json_schema"]

schemars/src/json_schema_impls/arrayvec.rs

@@ -0,0 +1,33 @@
+use crate::gen::SchemaGenerator;
+use crate::schema::*;
+use crate::JsonSchema;
+use arrayvec::{Array, ArrayString, ArrayVec};
+use std::convert::TryInto;
+
+// Do not set maxLength on the schema as that describes length in characters, but we only
+// know max length in bytes.
+forward_impl!((<A> JsonSchema for ArrayString<A> where A: Array<Item = u8> + Copy) => String);
+
+impl<A: Array> JsonSchema for ArrayVec<A>
+where
+    A::Item: JsonSchema,
+{
+    no_ref_schema!();
+
+    fn schema_name() -> String {
+        format!("Array_up_to_size_{}_of_{}", A::CAPACITY, A::Item::schema_name())
+    }
+
+    fn json_schema(gen: &mut SchemaGenerator) -> Schema {
+        SchemaObject {
+            instance_type: Some(InstanceType::Array.into()),
+            array: Some(Box::new(ArrayValidation {
+                items: Some(gen.subschema_for::<A::Item>().into()),
+                max_items: A::CAPACITY.try_into().ok(),
+                ..Default::default()
+            })),
+            ..Default::default()
+        }
+        .into()
+    }
+}

schemars/src/json_schema_impls/mod.rs

@@ -42,6 +42,10 @@ mod indexmap;
 mod either;
 #[cfg(feature = "uuid")]
 mod uuid;
+#[cfg(feature = "smallvec")]
+mod smallvec;
+#[cfg(feature = "arrayvec")]
+mod arrayvec;
 mod core;
 mod ffi;
 mod maps;

schemars/src/json_schema_impls/smallvec.rs

@@ -0,0 +1,6 @@
+use crate::gen::SchemaGenerator;
+use crate::schema::*;
+use crate::JsonSchema;
+use smallvec::{Array, SmallVec};
+
+forward_impl!((<A: Array> JsonSchema for SmallVec<A> where A::Item: JsonSchema) => Vec<A::Item>);

schemars/tests/arrayvec.rs

@@ -0,0 +1,13 @@
+mod util;
+use arrayvec::{ArrayString, ArrayVec};
+use util::*;
+
+#[test]
+fn arrayvec() -> TestResult {
+    test_default_generated_schema::<ArrayVec::<[i32; 16]>>("arrayvec")
+}
+
+#[test]
+fn arrayvec_string() -> TestResult {
+    test_default_generated_schema::<ArrayString::<[u8; 16]>>("arrayvec_string")
+}

schemars/tests/expected/arrayvec.json

@@ -0,0 +1,10 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "title": "Array_up_to_size_16_of_int32",
+  "type": "array",
+  "items": {
+    "type": "integer",
+    "format": "int32"
+  },
+  "maxItems": 16
+}

schemars/tests/expected/arrayvec_string.json

@@ -0,0 +1,5 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "title": "String",
+  "type": "string"
+}

schemars/tests/expected/smallvec.json

@@ -0,0 +1,8 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "title": "Array_of_String",
+  "type": "array",
+  "items": {
+    "type": "string"
+  }
+}

schemars/tests/smallvec.rs

@@ -0,0 +1,8 @@
+mod util;
+use smallvec::SmallVec;
+use util::*;
+
+#[test]
+fn smallvec() -> TestResult {
+    test_default_generated_schema::<SmallVec<[String; 2]>>("smallvec")
+}