Add check for msbridge config files (#26)

lib/__tests__/msbridge.test.js

@@ -0,0 +1,43 @@
+jest.mock("fs");
+const { readdirSync } = require("fs");
+const { FatalError } = require("../errors");
+const hasMSBridgeConfig = require("../checks/msbridge");
+
+describe("Fail if yarn.lock exists", () => {
+  it("should fail for local config", () => {
+    jest
+      .mocked(readdirSync)
+      .mockImplementationOnce(() => [
+        "index.js",
+        ".msbridge.local.json",
+        "package.json",
+      ]);
+    expect(hasMSBridgeConfig()).toBeInstanceOf(FatalError);
+  });
+  it("should fail for amplify config", () => {
+    jest
+      .mocked(readdirSync)
+      .mockImplementationOnce(() => [
+        "index.js",
+        ".msbridge.amplify.json",
+        "package.json",
+      ]);
+    expect(hasMSBridgeConfig()).toBeInstanceOf(FatalError);
+  });
+  it("should fail for standard config", () => {
+    jest
+      .mocked(readdirSync)
+      .mockImplementationOnce(() => [
+        "index.js",
+        ".msbridge.json",
+        "package.json",
+      ]);
+    expect(hasMSBridgeConfig()).toBeInstanceOf(FatalError);
+  });
+  it("should not fail when no config", () => {
+    jest
+      .mocked(readdirSync)
+      .mockImplementationOnce(() => ["index.js", "package.json"]);
+    expect(hasMSBridgeConfig()).toBeUndefined();
+  });
+});

lib/checks/msbridge.js

@@ -0,0 +1,17 @@
+const { readdirSync } = require("fs");
+const { FatalError } = require("../errors");
+
+function hasMSBridgeConfig() {
+  try {
+    const allRootFiles = readdirSync(".");
+    for (const file of allRootFiles) {
+      if (file.startsWith(".msbridge") && file.endsWith(".json")) {
+        return new FatalError("Unexpected " + file + " file detected");
+      }
+    }
+  } catch (e) {
+    return undefined;
+  }
+}
+
+module.exports = hasMSBridgeConfig;