Enable eriving JsonSchema when fields are in remote crates

schemars/tests/expected/remote_derive.json

@@ -0,0 +1,44 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "title": "Process",
+  "type": "object",
+  "properties": {
+    "command_line": {
+      "type": "string"
+    },
+    "system_cpu_time": {
+      "$ref": "#/definitions/DurationDef"
+    },
+    "user_cpu_time": {
+      "$ref": "#/definitions/DurationDef"
+    },
+    "wall_time": {
+      "$ref": "#/definitions/DurationDef"
+    }
+  },
+  "required": [
+    "command_line",
+    "system_cpu_time",
+    "user_cpu_time",
+    "wall_time"
+  ],
+  "definitions": {
+    "DurationDef": {
+      "type": "object",
+      "properties": {
+        "nanos": {
+          "type": "integer",
+          "format": "int32"
+        },
+        "secs": {
+          "type": "integer",
+          "format": "int64"
+        }
+      },
+      "required": [
+        "nanos",
+        "secs"
+      ]
+    }
+  }
+}

schemars/tests/remote_derive.rs

@@ -0,0 +1,37 @@
+mod util;
+
+use other_crate::Duration;
+use schemars::JsonSchema;
+use util::*;
+
+mod other_crate {
+    #[derive(Debug)]
+    pub struct Duration {
+        pub secs: i64,
+        pub nanos: i32,
+    }
+}
+
+#[derive(Debug, JsonSchema)]
+#[serde(remote = "Duration")]
+struct DurationDef {
+    secs: i64,
+    nanos: i32,
+}
+
+#[derive(Debug, JsonSchema)]
+struct Process {
+    command_line: String,
+    #[serde(with = "DurationDef")]
+    wall_time: Duration,
+    #[serde(with = "DurationDef")]
+    user_cpu_time: Duration,
+    #[serde(deserialize_with = "some_serialize_function")]
+    #[schemars(with = "DurationDef")]
+    system_cpu_time: Duration,
+}
+
+#[test]
+fn remote_derive_json_schema() -> TestResult {
+    test_default_generated_schema::<Process>("remote_derive")
+}