fix: Updates default http output binding (#308)

This updates the default value for the name of the HTTP output binding from $return to $res to work around an issue that existing within the Azure core tools http runtime..

A bug exists in the Azure core tools http runtime that evaluates $return binding incorrectly which causes serialization issues when returning arrays within an HTTP response.
Azure/azure-functions-nodejs-worker#228

Author: wbreza

src/services/azureKeyVaultService.ts

@@ -2,7 +2,7 @@ import Serverless from "serverless";
 import { BaseService } from "./baseService";
 import { FunctionAppService } from "./functionAppService";
 import { KeyVaultManagementClient } from "@azure/arm-keyvault";
-import { KeyPermissions, SecretPermissions, Vault } from "@azure/arm-keyvault/esm/models/index";
+import { Vault, SecretPermissions } from "@azure/arm-keyvault/esm/models";
 
 /**
  * Defines the Azure Key Vault configuration

src/shared/binding.test.ts

@@ -21,4 +21,51 @@ describe("Bindings", () => {
     BindingUtils.getBindingsMetaData(sls);
     expect(sls.cli.log).toBeCalledWith("Parsing Azure Functions Bindings.json...");
   });
+
+  it("Http output bindings should default to 'res'", () => {
+    const binding = BindingUtils.getHttpOutBinding();
+
+    expect(binding).toMatchObject({
+      type: "http",
+      direction: "out",
+      name: "res"
+    });
+  });
+
+  it("Gets the http binding with default settings", () => {
+    const serverless = MockFactory.createTestServerless();
+    const parsedBindings = BindingUtils.getBindingsMetaData(serverless);
+    const bindingType = "http";
+
+    const bindingTypes = parsedBindings.bindingTypes;
+    const bindingTypeIndex = bindingTypes.indexOf(bindingType);
+    const bindingSettings = parsedBindings.bindingSettings[bindingTypeIndex];
+
+    const binding = BindingUtils.getBinding(bindingType, bindingSettings, {});
+
+    expect(binding).toMatchObject({
+      type: "http",
+      direction: "out",
+      name: "res",
+    });
+  });
+
+  it("Gets the http binding with custom name", () => {
+    const serverless = MockFactory.createTestServerless();
+    const parsedBindings = BindingUtils.getBindingsMetaData(serverless);
+    const bindingType = "http";
+    const userSettings = { name: "custom" };
+
+    const bindingTypes = parsedBindings.bindingTypes;
+    const bindingTypeIndex = bindingTypes.indexOf(bindingType);
+    const bindingSettings = parsedBindings.bindingSettings[bindingTypeIndex];
+
+    const binding = BindingUtils.getBinding(bindingType, bindingSettings, userSettings);
+
+    expect(binding).toMatchObject({
+      type: "http",
+      direction: "out",
+      name: userSettings.name,
+    });
+  });
 });

src/shared/bindings.ts

@@ -57,15 +57,12 @@ export class BindingUtils {
     return bindingUserSettingsMetaData;
   }
 
-  public static getHttpOutBinding(bindingUserSettings) {
+  public static getHttpOutBinding() {
     const binding = {};
 
     binding[constants.type] = "http";
     binding[constants.direction] = constants.outDirection;
-    binding[constants.name] = "$return";
-    if (bindingUserSettings[constants.webHookType]) {
-      binding[constants.name] = "res";
-    }
+    binding[constants.name] = "res";
 
     return binding;
   }

src/shared/utils.ts

@@ -78,7 +78,7 @@ export class Utils {
     }
 
     if (bindingType === constants.httpTrigger) {
-      bindings.push(BindingUtils.getHttpOutBinding(bindingUserSettings));
+      bindings.push(BindingUtils.getHttpOutBinding());
     }
 
     functionsJson.bindings = bindings;