Throw error if duplicate names [fix]

overlookmotel · Dec 30, 2019 · a9d3e8a · a9d3e8a
1 parent 1d46dfc
commit a9d3e8a
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Showing 2 changed files with 11 additions and 0 deletions.
diff --git a/lib/index.js b/lib/index.js
@@ -14,9 +14,14 @@ module.exports = function makeSymbols(namespace, names, options) {
 	if (!isFullString(namespace)) throw new TypeError('namespace must be a string');
 	if (!isArray(names)) throw new TypeError('names must be an array of strings');
 
+	const namesSet = new Set();
 	for (const name of names) {
 		if (!isFullString(name)) throw new TypeError('names must be an array of strings');
 		if (name.toUpperCase() !== name) throw new Error('symbol names must be all capitalized');
+		if (namesSet.has(name)) {
+			throw new Error(`symbol names must be unique - '${name}' was duplicated`);
+		}
+		namesSet.add(name);
 	}
 
 	const symbols = {};

diff --git a/test/index.test.js b/test/index.test.js
@@ -73,6 +73,12 @@ describe('throws error if', () => {
 				makeSymbols('foo', ['BAR', 'Qux']);
 			}).toThrowWithMessage(Error, 'symbol names must be all capitalized');
 		});
+
+		it('contains duplicates', () => {
+			expect(() => {
+				makeSymbols('foo', ['BAR', 'QUX', 'BAR']);
+			}).toThrowWithMessage(Error, "symbol names must be unique - 'BAR' was duplicated");
+		});
 	});
 
 	describe('options', () => {