1 files changed, 54 insertions, 0 deletions
diff --git a/node_modules/release-zalgo/lib/unwrapSync.js b/node_modules/release-zalgo/lib/unwrapSync.js
new file mode 100644
index 000000000..baa130b18
--- /dev/null
+++ b/node_modules/release-zalgo/lib/unwrapSync.js
@@ -0,0 +1,54 @@
+'use strict'
+
+const ExtendableError = require('es6-error')
+
+const constants = require('./constants')
+
+class UnwrapError extends ExtendableError {
+  constructor (thenable) {
+    super('Could not unwrap asynchronous thenable')
+    this.thenable = thenable
+  }
+}
+
+// Logic is derived from the Promise Resolution Procedure, as described in the
+// Promises/A+ specification: https://promisesaplus.com/#point-45
+//
+// Note that there is no cycle detection.
+function unwrapSync (x) {
+  if (!x || typeof x !== 'object' && typeof x !== 'function') {
+    return x
+  }
+
+  const then = x.then
+  if (typeof then !== 'function') return x
+
+  let state = constants.PENDING
+  let value
+  const unwrapValue = y => {
+    if (state === constants.PENDING) {
+      state = constants.RESOLVED
+      value = y
+    }
+  }
+  const unwrapReason = r => {
+    if (state === constants.PENDING) {
+      state = constants.REJECTED
+      value = r
+    }
+  }
+  then.call(x, unwrapValue, unwrapReason)
+
+  if (state === constants.PENDING) {
+    state = constants.ASYNC
+    throw new UnwrapError(x)
+  }
+
+  if (state === constants.RESOLVED) {
+    return unwrapSync(value)
+  }
+
+  // state === REJECTED
+  throw value
+}
+module.exports = unwrapSync