Add asSet (#173)

* add asSet accessor

env-var.d.ts

@@ -73,6 +73,12 @@ type PublicAccessors = {
    */
   asArray: (input: string, delimiter?: string) => Array<string>;
 
+  /**
+   * Reads an environment variable as a string, then splits it on each occurrence of the specified delimiter.
+   * By default a comma is used as the delimiter. For example a var set to "1,2,3" would become new Set(['1', '2', '3']).
+   */
+  asSet: (input: string, delimiter?: string) => Set<string>;
+
   /**
    * Attempt to parse the variable to a Boolean. Throws an exception if parsing fails.
    * The var must be set to either "true", "false" (upper or lowercase), 0 or 1 to succeed.
@@ -178,6 +184,12 @@ interface VariableAccessors <AlternateType = unknown> {
    */
   asArray: (delimiter?: string) => AlternateType extends undefined ? undefined|Array<string> : Array<string>;
 
+  /**
+   * Reads an environment variable as a string, then splits it on each occurrence of the specified delimiter.
+   * By default a comma is used as the delimiter. For example a var set to "1,2,3" would become new Set(['1', '2', '3']).
+   */
+  asSet: (delimiter?: string) => AlternateType extends undefined ? undefined|Set<string> : Set<string>;
+
   /**
    * Attempt to parse the variable to a Boolean. Throws an exception if parsing fails.
    * The var must be set to either "true", "false" (upper or lowercase), 0 or 1 to succeed.

lib/accessors/index.js

@@ -1,5 +1,6 @@
 module.exports = {
   asArray: require('./array'),
+  asSet: require('./set'),
 
   asBoolStrict: require('./bool-strict'),
   asBool: require('./bool'),

lib/accessors/set.js

@@ -0,0 +1,11 @@
+'use strict'
+
+const asArray = require('./array')
+
+module.exports = function asSet (value, delimiter) {
+  if (!value.length) {
+    return new Set()
+  } else {
+    return new Set(asArray(value, delimiter))
+  }
+}

test/index.js

@@ -20,6 +20,7 @@ describe('env-var', function () {
     JSON_ARRAY: '[1,2,3]',
     COMMA_ARRAY: '1,2,3',
     EMPTY_ARRAY: '',
+    DUPLICATE_ARRAY: '1,1,2,2,3,3',
     ARRAY_WITHOUT_DELIMITER: 'value',
     ARRAY_WITH_DELIMITER: 'value,',
     ARRAY_WITH_DELIMITER_PREFIX: ',value',
@@ -539,6 +540,40 @@ describe('env-var', function () {
     })
   })
 
+  describe('#asSet', function () {
+    it('should return an empty set when not set', function () {
+      expect(mod.get('.NOPE.').asSet()).to.deep.equal(undefined)
+    })
+
+    it('should return a set that was split on commas', function () {
+      expect(mod.get('COMMA_ARRAY').asSet()).to.deep.equal(new Set(['1', '2', '3']))
+    })
+
+    it('should return a set that was split on dashes', function () {
+      expect(mod.get('DASH_ARRAY').asSet('-')).to.deep.equal(new Set(['1', '2', '3']))
+    })
+
+    it('should return an empty set if empty env var was set', function () {
+      expect(mod.get('EMPTY_ARRAY').asSet()).to.deep.equal(new Set())
+    })
+
+    it('should return set with only one value if env var doesn\'t contain delimiter', function () {
+      expect(mod.get('ARRAY_WITHOUT_DELIMITER').asSet()).to.deep.equal(new Set(['value']))
+    })
+
+    it('should return set with only one value if env var contain delimiter', function () {
+      expect(mod.get('ARRAY_WITH_DELIMITER').asSet()).to.deep.equal(new Set(['value']))
+    })
+
+    it('should return set with only one value if env var contain delimiter as prefix', function () {
+      expect(mod.get('ARRAY_WITH_DELIMITER_PREFIX').asSet()).to.deep.equal(new Set(['value']))
+    })
+
+    it('should return a set of unique values', function () {
+      expect(mod.get('DUPLICATE_ARRAY').asSet()).to.deep.equal(new Set(['1', '2', '3']))
+    })
+  })
+
   describe('#asPortNumber', function () {
     it('should raise an error for ports less than 0', function () {
       process.env.PORT_NUMBER = '-2'

test/types/index.ts

@@ -196,6 +196,20 @@ describe('typescript tests', () => {
       })
     })
 
+    describe('#asSet', () => {
+      it('should return a Set of strings', () => {
+        const set = env.accessors.asSet('1,2,3');
+
+        expect(set).to.eql(new Set(['1', '2', '3']));
+      });
+
+      it('should return a Set of strings split by period chars', () => {
+        const set = env.accessors.asSet('1.2.3', '.');
+
+        expect(set).to.eql(new Set(['1', '2', '3']));
+      });
+    });
+
     describe('#asInt', () => {
       it('should return an integer', () => {
         const ret = env.accessors.asInt('1')

tsconfig.json

@@ -1,6 +1,7 @@
 {
   "compilerOptions": {
     "sourceMap": false,
+    "lib": ["es2015"],
     "target": "es5",
     "moduleResolution": "node",
     "skipLibCheck": false,