feat(parse): allow parsing straight into a single IntegrityMetadata object

Author: zkat

Diff for: README.md

@@ -92,6 +92,10 @@ will be an `Integrity` instance that has this shape:
 }
 ```
 
+If `opts.single` is truthy, a single `IntegrityMetadata` object will be
+returned. That is, a single object that looks like `{algorithm, digest,
+options}`, as opposed to a larger object with multiple of these.
+
 If `opts.strict` is truthy, the resulting object will be filtered such that
 it strictly follows the Subresource Integrity spec, throwing away any entries
 with any invalid components. This also means a restricted set of algorithms

Diff for: index.js

@@ -102,6 +102,9 @@ function parse (sri, opts) {
 function _parse (integrity, opts) {
   // 3.4.3. Parse metadata
   // https://w3c.github.io/webappsec-subresource-integrity/#parse-metadata
+  if (opts.single) {
+    return new IntegrityMetadata(integrity, opts)
+  }
   return integrity.trim().split(/\s+/).reduce((acc, string) => {
     const metadata = new IntegrityMetadata(string, opts)
     if (metadata.algorithm && metadata.digest) {

Diff for: test/parse.js

@@ -12,7 +12,7 @@ function hash (data, algorithm) {
   return crypto.createHash(algorithm).update(data).digest('base64')
 }
 
-test('parses single-entry inegrity string', t => {
+test('parses single-entry integrity string', t => {
   const sha = hash(TEST_DATA, 'sha512')
   const integrity = `sha512-${sha}`
   t.deepEqual(ssri.parse(integrity), {
@@ -26,6 +26,18 @@ test('parses single-entry inegrity string', t => {
   t.done()
 })
 
+test('can parse single-entry string directly into IntegrityMetadata', t => {
+  const sha = hash(TEST_DATA, 'sha512')
+  const integrity = `sha512-${sha}`
+  t.deepEqual(ssri.parse(integrity, {single: true}), {
+    source: integrity,
+    digest: sha,
+    algorithm: 'sha512',
+    options: []
+  }, 'single entry parsed into single IntegrityMetadata instance')
+  t.done()
+})
+
 test('accepts IntegrityMetadata-likes as input', t => {
   const algorithm = 'sha512'
   const digest = hash(TEST_DATA, 'sha512')