Return false instead of throwing in validate() for a bad npm namespace

src/purl-type.js

@@ -305,9 +305,12 @@ module.exports = {
                             return false
                         }
                         if (code0 !== 64 /*'@'*/) {
-                            throw new PurlError(
-                                `npm "namespace" component must start with an "@" character`
-                            )
+                            if (throws) {
+                                throw new PurlError(
+                                    `npm "namespace" component must start with an "@" character`
+                                )
+                            }
+                            return false
                         }
                         const namespaceWithoutAtSign = namespace.slice(1)
                         if (

test/package-url.spec.js

@@ -31,7 +31,7 @@ const TEST_FILE = [
     ...require('./data/contrib-tests.json')
 ]
 
-const { PackageURL } = require('../src/package-url')
+const { PackageURL, PurlType } = require('../src/package-url')
 
 function getNpmId(purl) {
     const { name, namespace } = purl
@@ -545,4 +545,24 @@ describe('PackageURL', function () {
             )
         })
     })
+
+    describe('npm validate', function () {
+        it('should return false rather than throw for a bad namespace when throws is false', function () {
+            const purl = { type: 'npm', namespace: 'foo', name: 'bar' }
+            assert.strictEqual(PurlType.npm.validate(purl, false), false)
+        })
+
+        it('should still throw for a bad namespace when throws is true', function () {
+            const purl = { type: 'npm', namespace: 'foo', name: 'bar' }
+            assert.throws(
+                () => PurlType.npm.validate(purl, true),
+                /npm "namespace" component must start with an "@" character/
+            )
+        })
+
+        it('should accept a scoped namespace when throws is false', function () {
+            const purl = { type: 'npm', namespace: '@scope', name: 'bar' }
+            assert.strictEqual(PurlType.npm.validate(purl, false), true)
+        })
+    })
 })