feat: add SmithyException, isa and DocumentType to smithy-client (#546)

Author: Chase Coalwell

packages/smithy-client/src/document-type.ts

@@ -0,0 +1,9 @@
+/**
+ * Smithy document type values.
+ */
+export namespace DocumentType {
+  export type Value = Scalar | Structure | List;
+  export type Scalar = string | number | boolean | null;
+  export type Structure = { [member: string]: Value };
+  export interface List extends Array<Value> {}
+}

packages/smithy-client/src/exception.ts

@@ -0,0 +1,20 @@
+/**
+ * Type that is implemented by all Smithy shapes marked with the
+ * error trait.
+ */
+export interface SmithyException {
+  /**
+   * The shape ID name of the exception.
+   */
+  readonly __type: string;
+
+  /**
+   * Whether the client or server are at fault.
+   */
+  readonly $fault: "client" | "server";
+
+  /**
+   * The service that encountered the exception.
+   */
+  readonly $service?: string;
+}

packages/smithy-client/src/index.ts

@@ -1,2 +1,5 @@
 export * from "./client";
 export * from "./command";
+export * from "./document-type";
+export * from "./exception";
+export * from "./isa";

packages/smithy-client/src/isa.ts

@@ -0,0 +1,8 @@
+/**
+ * Checks if the given value is a Smithy structure of the given type.
+ */
+export function isa<T>(o: any, ...ids: string[]): o is T {
+  return (
+    typeof o === "object" && "__type" in o && ids.indexOf(o["__type"]) > -1
+  );
+}