fix(no-unnecessary-collection): spread element (#289)

Resolves #288

Author: JasonWeinzierl

src/etc/is.ts

@@ -134,6 +134,10 @@ export function isRestElement(node: TSESTree.Node): node is TSESTree.RestElement
   return node.type === AST_NODE_TYPES.RestElement;
 }
 
+export function isSpreadElement(node: TSESTree.Node): node is TSESTree.SpreadElement {
+  return node.type === AST_NODE_TYPES.SpreadElement;
+}
+
 export function isThisExpression(node: TSESTree.Node): node is TSESTree.ThisExpression {
   return node.type === AST_NODE_TYPES.ThisExpression;
 }

src/rules/no-unnecessary-collection.ts

@@ -2,7 +2,7 @@ import {
   TSESTree as es,
 } from '@typescript-eslint/utils';
 import { MULTIPLE_OBSERVABLE_ACCEPTING_STATIC_OBSERVABLE_CREATORS, SOURCES_OBJECT_ACCEPTING_STATIC_OBSERVABLE_CREATORS } from '../constants';
-import { getTypeServices, isArrayExpression, isObjectExpression, isProperty } from '../etc';
+import { getTypeServices, isArrayExpression, isObjectExpression, isProperty, isSpreadElement } from '../etc';
 import { ruleCreator } from '../utils';
 
 export const noUnnecessaryCollectionRule = ruleCreator({
@@ -71,7 +71,7 @@ export const noUnnecessaryCollectionRule = ruleCreator({
       }
 
       // Single rest parameter argument.
-      if (args.length === 1 && couldBeObservable(firstArg)) {
+      if (args.length === 1 && !isSpreadElement(firstArg) && couldBeObservable(firstArg)) {
         context.report({
           messageId: 'forbidden',
           node: node.callee,

tests/rules/no-unnecessary-collection.test.ts

@@ -38,6 +38,13 @@ ruleTester({ types: true }).run('no-unnecessary-collection', noUnnecessaryCollec
       const b$ = of(2);
       const merged$ = merge(a$, b$);
     `,
+    stripIndent`
+      // merge with spread
+      import { merge, of } from "rxjs";
+
+      const arr = [of(1), of(2)];
+      const merged$ = merge(...arr);
+    `,
     stripIndent`
       // zip with multiple observables
       import { zip, of } from "rxjs";