grpc-js-core: remove simple uses of lodash

This commit removes lodash as a production dependency. It
remains as a devDependency because it's used in tests, but the
uses in the src/ directory were easily replaced with vanilla
JavaScript.

packages/grpc-js-core/package.json

@@ -20,6 +20,7 @@
     "@types/node": "^10.5.4",
     "clang-format": "^1.0.55",
     "gts": "^0.5.1",
+    "lodash": "^4.17.4",
     "typescript": "~2.7.0"
   },
   "contributors": [
@@ -41,7 +42,6 @@
     "posttest": "npm run check"
   },
   "dependencies": {
-    "lodash": "^4.17.4",
     "semver": "^5.5.0"
   },
   "files": [

packages/grpc-js-core/src/call-credentials.ts

@@ -1,5 +1,3 @@
-import {map} from 'lodash';
-
 import {Metadata} from './metadata';
 
 export type CallMetadataOptions = {
@@ -53,7 +51,7 @@ class ComposedCallCredentials extends CallCredentials {
   async generateMetadata(options: CallMetadataOptions): Promise<Metadata> {
     const base: Metadata = new Metadata();
     const generated: Metadata[] = await Promise.all(
-        map(this.creds, (cred) => cred.generateMetadata(options)));
+        this.creds.map((cred) => cred.generateMetadata(options)));
     for (const gen of generated) {
       base.merge(gen);
     }

packages/grpc-js-core/src/filter-stack.ts

@@ -1,5 +1,3 @@
-import {map} from 'lodash';
-
 import {Call, StatusObject, WriteObject} from './call-stream';
 import {Filter, FilterFactory} from './filter';
 import {Metadata} from './metadata';
@@ -63,6 +61,6 @@ export class FilterStackFactory implements FilterFactory<FilterStack> {
 
   createFilter(callStream: Call): FilterStack {
     return new FilterStack(
-        map(this.factories, (factory) => factory.createFilter(callStream)));
+        this.factories.map((factory) => factory.createFilter(callStream)));
   }
 }

packages/grpc-js-core/src/make-client.ts

@@ -1,5 +1,3 @@
-import * as _ from 'lodash';
-
 import {ChannelCredentials} from './channel-credentials';
 import {ChannelOptions} from './channel-options';
 import {Client} from './client';
@@ -73,10 +71,11 @@ export function makeClientConstructor(
     [methodName: string]: Function;
   }
 
-  _.each(methods, (attrs, name) => {
+  Object.keys(methods).forEach((name) => {
+    const attrs = methods[name];
     let methodType: keyof typeof requesterFuncs;
     // TODO(murgatroid99): Verify that we don't need this anymore
-    if (_.startsWith(name, '$')) {
+    if (typeof name === 'string' && name.charAt(0) === '$') {
       throw new Error('Method names cannot start with $');
     }
     if (attrs.requestStream) {
@@ -94,11 +93,11 @@ export function makeClientConstructor(
     }
     const serialize = attrs.requestSerialize;
     const deserialize = attrs.responseDeserialize;
-    const methodFunc = _.partial(
-        requesterFuncs[methodType], attrs.path, serialize, deserialize);
+    const methodFunc =
+        partial(requesterFuncs[methodType], attrs.path, serialize, deserialize);
     ServiceClientImpl.prototype[name] = methodFunc;
     // Associate all provided attributes with the method
-    _.assign(ServiceClientImpl.prototype[name], attrs);
+    Object.assign(ServiceClientImpl.prototype[name], attrs);
     if (attrs.originalName) {
       ServiceClientImpl.prototype[attrs.originalName] =
           ServiceClientImpl.prototype[name];
@@ -110,6 +109,15 @@ export function makeClientConstructor(
   return ServiceClientImpl;
 }
 
+function partial(
+    fn: Function, path: string, serialize: Function,
+    deserialize: Function): Function {
+  // tslint:disable-next-line:no-any
+  return function(this: any, ...args: any[]) {
+    return fn.call(this, path, serialize, deserialize, ...args);
+  };
+}
+
 export type GrpcObject = {
   [index: string]: GrpcObject|ServiceClientConstructor;
 };