add filter option to retry() and retryable() to allow for error filtering and control of retry flow. Resolves #1256.

3 files changed, 154 insertions, 3 deletions

diff --git a/lib/retry.js b/lib/retry.js
index 8163ad9..a700516 100644
--- a/lib/retry.js
+++ b/lib/retry.js
@@ -19,6 +19,10 @@ import constant from 'lodash/constant';
  * * `interval` - The time to wait between retries, in milliseconds.  The
  *   default is `0`. The interval may also be specified as a function of the
  *   retry count (see example).
+ * * `filter` - Synchronous function that is invoked on erroneous result with the
+ *   the error. If it returns `true` the retry attempts will continue, if the
+ *   function returns `false` the retry flow is aborting with the current
+ *   attempt's error and result being returned to the final callback.
  * * If `opts` is a number, the number specifies the number of times to retry,
  *   with the default interval of `0`.
  * @param {Function} task - A function which receives two arguments: (1) a
@@ -62,6 +66,16 @@ import constant from 'lodash/constant';
  *     // do something with the result
  * });
  *
+ * // try calling apiMethod only when error condition satisfies, all other
+ * // errors will abort the retry control flow and return to final callback
+ * async.retry({
+ *   filter: function(err) {
+ *     return err.message === 'Temporary error'; // only retry on a specific error
+ *   }
+ * }, apiMethod, function(err, result) {
+ *     // do something with the result
+ * });
+ *
  * // It can also be embedded within other control flow functions to retry
  * // individual methods that are not as reliable, like this:
  * async.auto({
@@ -70,6 +84,7 @@ import constant from 'lodash/constant';
  * }, function(err, results) {
  *     // do something with the results
  * });
+ *
  */
 export default function retry(opts, task, callback) {
     var DEFAULT_TIMES = 5;
@@ -87,6 +102,10 @@ export default function retry(opts, task, callback) {
             acc.intervalFunc = typeof t.interval === 'function' ?
                 t.interval :
                 constant(+t.interval || DEFAULT_INTERVAL);
+
+            if(typeof t.filter === 'function') {
+                acc.filter = t.filter;
+            }
         } else if (typeof t === 'number' || typeof t === 'string') {
             acc.times = +t || DEFAULT_TIMES;
         } else {
@@ -94,7 +113,6 @@ export default function retry(opts, task, callback) {
         }
     }
 
-
     if (arguments.length < 3 && typeof opts === 'function') {
         callback = task || noop;
         task = opts;
@@ -111,7 +129,16 @@ export default function retry(opts, task, callback) {
     function retryAttempt() {
         task(function(err) {
             if (err && attempt++ < options.times) {
-                setTimeout(retryAttempt, options.intervalFunc(attempt));
+                var proceed = true;
+                if(options.filter) {
+                    proceed = options.filter(err);
+                }
+
+                if(proceed) {
+                    setTimeout(retryAttempt, options.intervalFunc(attempt));
+                } else {
+                    callback.apply(null, arguments);
+                }
             } else {
                 callback.apply(null, arguments);
             }
diff --git a/mocha_test/retry.js b/mocha_test/retry.js
index 4d7b241..1cfbcab 100644
--- a/mocha_test/retry.js
+++ b/mocha_test/retry.js
@@ -156,5 +156,105 @@ describe("retry", function () {
         async.retry(5, fn, function(err, result) {
             expect(result).to.be.eql({a: 1});
         });
-    })
+    });
+
+    it('retry when all attempts fail and error filter returns true',function(done) {
+        var times = 3;
+        var callCount = 0;
+        var error = 'ERROR';
+        var special = 'SPECIAL_ERROR';
+        var erroredResult = 'RESULT';
+        function fn(callback) {
+            callCount++;
+            callback(error + callCount, erroredResult + callCount);
+        }
+        function filter(err) {
+            return err && err !== special;
+        }
+        var options = {
+            times: times,
+            filter: filter
+        };
+        async.retry(options, fn, function(err, result){
+            assert.equal(callCount, 3, "did not retry the correct number of times");
+            assert.equal(err, error + times, "Incorrect error was returned");
+            assert.equal(result, erroredResult + times, "Incorrect result was returned");
+            done();
+        });
+    });
+
+    it('retry when some attempts fail and error filter returns false at some invokation',function(done) {
+        var callCount = 0;
+        var error = 'ERROR';
+        var special = 'SPECIAL_ERROR';
+        var erroredResult = 'RESULT';
+        function fn(callback) {
+            callCount++;
+            var err = callCount === 2 ? special : error + callCount;
+            callback(err, erroredResult + callCount);
+        }
+        function filter(err) {
+            return err && err === error + callCount; // just a different pattern
+        }
+        var options = {
+            filter: filter
+        };
+        async.retry(options, fn, function(err, result){
+            assert.equal(callCount, 2, "did not retry the correct number of times");
+            assert.equal(err, special, "Incorrect error was returned");
+            assert.equal(result, erroredResult + 2, "Incorrect result was returned");
+            done();
+        });
+    });
+
+    it('retry with interval when some attempts fail and error filter returns false at some invokation',function(done) {
+        var interval = 50;
+        var callCount = 0;
+        var error = 'ERROR';
+        var erroredResult = 'RESULT';
+        var special = 'SPECIAL_ERROR';
+        var specialCount = 3;
+        function fn(callback) {
+            callCount++;
+            var err = callCount === specialCount ? special : error + callCount;
+            callback(err, erroredResult + callCount);
+        }
+        function filter(err) {
+            return err && err !== special;
+        }
+        var start = new Date().getTime();
+        async.retry({ interval: interval, filter: filter }, fn, function(err, result){
+            var now = new Date().getTime();
+            var duration = now - start;
+            assert(duration >= (interval * (specialCount - 1)),  'did not include interval');
+            assert.equal(callCount, specialCount, "did not retry the correct number of times");
+            assert.equal(err, special, "Incorrect error was returned");
+            assert.equal(result, erroredResult + specialCount, "Incorrect result was returned");
+            done();
+        });
+    });
+
+    it('retry when first attempt succeeds and error filter should not be called',function(done) {
+        var callCount = 0;
+        var error = 'ERROR';
+        var erroredResult = 'RESULT';
+        var filterCalled = false;
+        function fn(callback) {
+            callCount++;
+            callback(null, erroredResult + callCount);
+        }
+        function filter(err) {
+            filterCalled = true;
+            return err && err === error;
+        }
+        var options = {
+            filter: filter
+        };
+        async.retry(options, fn, _.rest(function(args) {
+            assert.equal(callCount, 1, "did not retry the correct number of times");
+            expect(args).to.be.eql([null, erroredResult + callCount]);
+            assert.equal(filterCalled, false, "filter function was called");
+            done();
+        }));
+    });
 });
diff --git a/mocha_test/retryable.js b/mocha_test/retryable.js
index 7147269..0a229f5 100644
--- a/mocha_test/retryable.js
+++ b/mocha_test/retryable.js
@@ -21,6 +21,30 @@ describe('retryable', function () {
         }, 15);
     });
 
+    it('basics with filter function', function (done) {
+        var calls = 0;
+        var special = 'special';
+        var opts = {
+            filter: function(err) {
+                return err == special;
+            }
+        };
+        var retryableTask = async.retryable(opts, function (arg, cb) {
+            calls++;
+            expect(arg).to.equal(42);
+            cb(calls === 3 ? 'fail' : special);
+        });
+
+        retryableTask(42, function (err) {
+            expect(err).to.equal('fail');
+            expect(calls).to.equal(3);
+            done();
+        });
+
+        setTimeout(function () {
+        }, 15);
+    });
+
     it('should work as an embedded task', function(done) {
         var retryResult = 'RETRY';
         var fooResults;