chore: add helper method for parsing booleans

This adds a helper for parsing booleans from strings. Previously a
simple `=== "true"` check was being performed, but this implies that
anything that isn't that particular string is false.

Author: JordonPhillips

packages/smithy-client/src/boolean.spec.ts

@@ -0,0 +1,47 @@
+import { parseBoolean } from "./boolean";
+
+describe("parseBoolean", () => {
+  it('Returns true for "true"', () => {
+    expect(parseBoolean("true")).toEqual(true);
+  });
+
+  it('Returns false for "false"', () => {
+    expect(parseBoolean("false")).toEqual(false);
+  });
+
+  it("Throws an error on invalid input", () => {
+    // These are valid booleans in YAML
+    expect(() => parseBoolean("y" as any)).toThrowError();
+    expect(() => parseBoolean("Y" as any)).toThrowError();
+    expect(() => parseBoolean("yes" as any)).toThrowError();
+    expect(() => parseBoolean("Yes" as any)).toThrowError();
+    expect(() => parseBoolean("YES" as any)).toThrowError();
+    expect(() => parseBoolean("n" as any)).toThrowError();
+    expect(() => parseBoolean("N" as any)).toThrowError();
+    expect(() => parseBoolean("no" as any)).toThrowError();
+    expect(() => parseBoolean("No" as any)).toThrowError();
+    expect(() => parseBoolean("NO" as any)).toThrowError();
+    expect(() => parseBoolean("True" as any)).toThrowError();
+    expect(() => parseBoolean("TRUE" as any)).toThrowError();
+    expect(() => parseBoolean("False" as any)).toThrowError();
+    expect(() => parseBoolean("FALSE" as any)).toThrowError();
+    expect(() => parseBoolean("on" as any)).toThrowError();
+    expect(() => parseBoolean("On" as any)).toThrowError();
+    expect(() => parseBoolean("ON" as any)).toThrowError();
+    expect(() => parseBoolean("off" as any)).toThrowError();
+    expect(() => parseBoolean("Off" as any)).toThrowError();
+    expect(() => parseBoolean("OFF" as any)).toThrowError();
+
+    // These would be resolve to false using Boolean
+    expect(() => parseBoolean(0 as any)).toThrowError();
+    expect(() => parseBoolean(null as any)).toThrowError();
+    expect(() => parseBoolean("" as any)).toThrowError();
+    expect(() => parseBoolean(false as any)).toThrowError();
+
+    // These would resolve to true using Boolean
+    expect(() => parseBoolean(true as any)).toThrowError();
+    expect(() => parseBoolean("Su Lin" as any)).toThrowError();
+    expect(() => parseBoolean([] as any)).toThrowError();
+    expect(() => parseBoolean({} as any)).toThrowError();
+  });
+});

packages/smithy-client/src/boolean.ts

@@ -0,0 +1,16 @@
+/**
+ * Give an input string, stritctly parses a boolean value.
+ *
+ * @param value The boolean string to parse.
+ * @returns true for "true", false for "false", otherwise an error is thrown.
+ */
+export function parseBoolean(value: "true" | "false"): boolean {
+  switch (value) {
+    case "true":
+      return true;
+    case "false":
+      return false;
+    default:
+      throw new Error(`Unable to parse boolean value "${value}"`);
+  }
+}

packages/smithy-client/src/index.ts

@@ -1,3 +1,4 @@
+export * from "./boolean";
 export * from "./client";
 export * from "./command";
 export * from "./document-type";