Replace lodash with built-ins where possible to reduce bundle size (#1766)

* add tslint rule to disallow lodash.isUndefined

* add tslint rule to disallow lodash.isNull

* apply fixes

packages/tslint-config/rules/noLodashIsnullRule.ts

@@ -0,0 +1,49 @@
+import * as Lint from 'tslint';
+import * as ts from 'typescript';
+
+export class Rule extends Lint.Rules.AbstractRule {
+    public static FAILURE_STRING = `Use built-in equivalent`;
+
+    public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
+        return this.applyWithFunction(sourceFile, walk);
+    }
+}
+
+function walk(ctx: Lint.WalkContext<void>): void {
+    // Recursively walk the AST starting with root node, `ctx.sourceFile`.
+    // Call the function `cb` (defined below) for each child.
+    return ts.forEachChild(ctx.sourceFile, cb);
+
+    function cb(node: ts.Node): void {
+        if (node.kind === ts.SyntaxKind.CallExpression) {
+            const firstChild = node.getChildAt(0, ctx.sourceFile);
+            if (
+                firstChild.kind === ts.SyntaxKind.PropertyAccessExpression &&
+                firstChild.getText(ctx.sourceFile) === '_.isNull'
+            ) {
+                return ctx.addFailureAtNode(node, Rule.FAILURE_STRING, getFix(node));
+            }
+        }
+        // Continue recursion into the AST by calling function `cb` for every child of the current node.
+        return ts.forEachChild(node, cb);
+    }
+
+    function getFix(node: ts.Node): Lint.Replacement {
+        const isNegated =
+            node.parent.kind === ts.SyntaxKind.PrefixUnaryExpression && node.parent.getText(ctx.sourceFile)[0] === '!';
+        const args = node.getChildAt(2, ctx.sourceFile).getText(ctx.sourceFile);
+        if (isNegated) {
+            return new Lint.Replacement(
+                node.parent.getStart(ctx.sourceFile),
+                node.parent.getWidth(ctx.sourceFile),
+                `${args} !== null`,
+            );
+        } else {
+            return new Lint.Replacement(
+                node.getStart(ctx.sourceFile),
+                node.getWidth(ctx.sourceFile),
+                `${args} === null`,
+            );
+        }
+    }
+}