Merge pull request #520 from svozza/fromError-of

add _.of and _.fromError. Resolves #519.

CHANGELOG.md

@@ -5,6 +5,15 @@ This file does not aim to be comprehensive (you have git history for that),
 rather it lists changes that might impact your own code as a consumer of
 this library.
 
+2.10.0
+------
+### New additions
+* `of`: Creates a stream that sends a single value then ends. 
+  [#520](https://github.com/caolan/highland/pull/520).
+* `fromError`: Creates a stream that sends a single error then ends. 
+  [#520](https://github.com/caolan/highland/pull/520).  
+
+
 2.9.0
 -----
 ### New additions

lib/index.js

@@ -770,6 +770,41 @@ function Stream(/*optional*/xs, /*optional*/secondArg, /*optional*/mappingHint)
 }
 inherits(Stream, EventEmitter);
 
+/**
+ * Creates a stream that sends a single value then ends.
+ *
+ * @id of
+ * @name _.of(x)
+ * @param x - the value to send
+ * @section Utils
+ *
+ * _.of(1).toArray(_.log); // => [1]
+ */
+
+_.of = function (x) {
+    return _([x]);
+};
+
+/**
+ * Creates a stream that sends a single error then ends.
+ *
+ * @id fromError
+ * @name _.fromError(err)
+ * @param error - the error to send
+ * @section Utils
+ *
+ * _.fromError(new Error('Single Error')).toCallback(function (err, result) {
+ *     // err contains Error('Single Error') object
+ * }
+ */
+
+_.fromError = function (error) {
+    return _(function (push) {
+        push(error);
+        push(null, _.nil);
+    });
+};
+
 /**
  * adds a top-level _.foo(mystream) style export for Stream methods
  */

test/test.js

@@ -1079,6 +1079,31 @@ exports['generator throws error if push called after nil'] = function (test) {
     test.done();
 };
 
+exports.of = {
+    'creates stream of one item': function (test) {
+        test.expect(2);
+        _.of(1)
+            .toCallback(function (err, result) {
+                test.ifError(err);
+                test.same(result, 1);
+                test.done();
+            });
+    }
+};
+
+exports.fromError = {
+    'creates stream of one error': function (test) {
+        var error = new Error('This is an error');
+        test.expect(2);
+        _.fromError(error)
+            .toCallback(function (err, result) {
+                test.strictEqual(err, error);
+                test.strictEqual(result, void 0);
+                test.done();
+            });
+    }
+};
+
 exports['consume - throws error if push called after nil'] = function (test) {
     test.expect(1);
     var s = _([1, 2, 3]);