Add and export InvalidHeaderError

src/index.js

@@ -1,4 +1,5 @@
+import InvalidHeaderError from './invalid-header-error';
 import format from './format';
 import parse from './parse';
 
-export {format, parse};
+export {InvalidHeaderError, format, parse};

src/invalid-header-error.js

@@ -0,0 +1,10 @@
+const InvalidHeaderError = function InvalidHeaderError(message) {
+  this.name = 'InvalidHeaderError';
+  this.message = message;
+  this.stack = (new Error()).stack;
+};
+
+InvalidHeaderError.prototype = Object.create(TypeError.prototype);
+InvalidHeaderError.prototype.constructor = InvalidHeaderError;
+
+export default InvalidHeaderError;

src/parse.js

@@ -1,3 +1,4 @@
+import InvalidHeaderError from './invalid-header-error';
 import {isScheme, unquote} from './util';
 
 // lol dis
@@ -34,14 +35,14 @@ const parseProperties = (scheme, string) => {
 
 export default (str) => {
   if (typeof str !== 'string') {
-    throw new TypeError('Header value must be a string.');
+    throw new InvalidHeaderError('Header value must be a string.');
   }
 
   const start = str.indexOf(' ');
   const scheme = str.substr(0, start);
 
   if (!isScheme(scheme)) {
-    throw new TypeError(`Invalid scheme ${scheme}`);
+    throw new InvalidHeaderError(`Invalid scheme ${scheme}`);
   }
 
   return parseProperties(scheme, str.substr(start));

test/spec/invalid-header-error.spec.js

@@ -0,0 +1,16 @@
+import {expect} from 'chai';
+import InvalidHeaderError from '../../src/invalid-header-error';
+
+describe('InvalidHeaderError', () => {
+  it('should inherit from TypeError', () => {
+    expect(new InvalidHeaderError()).to.be.an.instanceof(TypeError);
+  });
+
+  it('should set given message', () => {
+    expect(new InvalidHeaderError('foobar').message).to.equal('foobar');
+  });
+
+  it('should set a stack trace', () => {
+    expect(new InvalidHeaderError().stack).to.not.be.undefined;
+  });
+});

test/spec/parse.spec.js

@@ -1,29 +1,30 @@
 import {expect} from 'chai';
+import InvalidHeaderError from '../../src/invalid-header-error';
 import parse from '../../src/parse';
 
 describe('parse', () => {
   it('should fail on invalid schemes', () => {
     expect(() => {
-      parse('@foo');
-    }).to.throw(TypeError);
+      parse('@ foo');
+    }).to.throw(InvalidHeaderError, 'Invalid scheme @');
   });
 
   it('should fail if a boolean', () => {
     expect(() => {
       parse(true);
-    }).to.throw(TypeError);
+    }).to.throw(InvalidHeaderError, 'Header value must be a string.');
   });
 
   it('should fail if an object', () => {
     expect(() => {
       parse({ });
-    }).to.throw(TypeError);
+    }).to.throw(InvalidHeaderError, 'Header value must be a string.');
   });
 
   it('should fail if null', () => {
     expect(() => {
       parse(null);
-    }).to.throw(TypeError);
+    }).to.throw(InvalidHeaderError, 'Header value must be a string.');
   });
 
   it('should coalesce many values', () => {