Treat :error and :error tuples as function failure

README.md

@@ -39,10 +39,15 @@ proceed_with(user_id)
 
 ## Semantics
 
-The call to `eventually` will succeed if the passed function returns some value
-other than `false` within the provided number of retries.  Otherwise, it will
-either raise a `Liveness` exception or reraise the last exception raised by the
-function.
+The call to `eventually` will succeed within the provided number of retries if
+the passed function returns some value other than:
+
+* `false`
+* `:error`
+* a tuple starting with `:error`
+
+Otherwise, it will either raise a `Liveness` exception or reraise the last
+exception raised by the function.
 
 By default, `eventually` will attempt to execute the function 250 times, every
 20 milliseconds. Both parameters can be altered by passing them to

lib/liveness.ex

@@ -16,13 +16,14 @@ defmodule Liveness do
   milliseconds, the next try will be attempted immediately after `f` returns.
 
   A function is deemed to have failed if it returns `false` or `nil` (a falsy
-  value), or if it crashes (exits, raises, or `:erlang.error`s out).
+  value), `:error` or a tuple starting with `:error`, or if it crashes (exits,
+  raises, or `:erlang.error`s out).
 
   If the function returns successfully, its return value becomes the value of
   the call to `eventually`.
 
-  If the function returns a falsy value (`false` or `nil`) upon the last try,
-  then the `Liveness` exception is raised.
+  If the function fails upon the last try, then the `Liveness` exception is
+  raised.
 
   If the function raises an exception upon the last try, this exception is
   re-raised by `eventually` with the *original* stacktrace.
@@ -45,7 +46,7 @@ defmodule Liveness do
 
     try do
       case f.() do
-        x when is_nil(x) or false == x ->
+        x when is_nil(x) or false == x or :error == x or (is_tuple(x) and elem(x, 0) == :error) ->
           sleep_remaining(started_at, interval)
           exception = %__MODULE__{message: "function returned #{inspect(x)}"}
           eventually(f, tries - 1, interval, exception, nil)

mix.exs

@@ -17,7 +17,7 @@ defmodule Liveness.MixProject do
   def application, do: []
 
   defp deps do
-    [{:ex_doc, "~> 0.21.2", only: :dev, runtime: false}]
+    [{:ex_doc, "~> 0.0", only: :dev, runtime: false}]
   end
 
   defp docs do

mix.lock

@@ -1,7 +1,9 @@
 %{
-  "earmark": {:hex, :earmark, "1.4.2", "3aa0bd23bc4c61cf2f1e5d752d1bb470560a6f8539974f767a38923bb20e1d7f", [:mix], [], "hexpm"},
-  "ex_doc": {:hex, :ex_doc, "0.21.2", "caca5bc28ed7b3bdc0b662f8afe2bee1eedb5c3cf7b322feeeb7c6ebbde089d6", [:mix], [{:earmark, "~> 1.3.3 or ~> 1.4", [hex: :earmark, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, repo: "hexpm", optional: false]}], "hexpm"},
-  "makeup": {:hex, :makeup, "1.0.0", "671df94cf5a594b739ce03b0d0316aa64312cee2574b6a44becb83cd90fb05dc", [:mix], [{:nimble_parsec, "~> 0.5.0", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm"},
-  "makeup_elixir": {:hex, :makeup_elixir, "0.14.0", "cf8b7c66ad1cff4c14679698d532f0b5d45a3968ffbcbfd590339cb57742f1ae", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm"},
-  "nimble_parsec": {:hex, :nimble_parsec, "0.5.1", "c90796ecee0289dbb5ad16d3ad06f957b0cd1199769641c961cfe0b97db190e0", [:mix], [], "hexpm"},
+  "earmark": {:hex, :earmark, "1.4.47", "7e7596b84fe4ebeb8751e14cbaeaf4d7a0237708f2ce43630cfd9065551f94ca", [:mix], [], "hexpm", "3e96bebea2c2d95f3b346a7ff22285bc68a99fbabdad9b655aa9c6be06c698f8"},
+  "earmark_parser": {:hex, :earmark_parser, "1.4.41", "ab34711c9dc6212dda44fcd20ecb87ac3f3fce6f0ca2f28d4a00e4154f8cd599", [:mix], [], "hexpm", "a81a04c7e34b6617c2792e291b5a2e57ab316365c2644ddc553bb9ed863ebefa"},
+  "ex_doc": {:hex, :ex_doc, "0.34.2", "13eedf3844ccdce25cfd837b99bea9ad92c4e511233199440488d217c92571e8", [:mix], [{:earmark_parser, "~> 1.4.39", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_c, ">= 0.1.0", [hex: :makeup_c, repo: "hexpm", optional: true]}, {:makeup_elixir, "~> 0.14 or ~> 1.0", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1 or ~> 1.0", [hex: :makeup_erlang, repo: "hexpm", optional: false]}, {:makeup_html, ">= 0.1.0", [hex: :makeup_html, repo: "hexpm", optional: true]}], "hexpm", "5ce5f16b41208a50106afed3de6a2ed34f4acfd65715b82a0b84b49d995f95c1"},
+  "makeup": {:hex, :makeup, "1.1.2", "9ba8837913bdf757787e71c1581c21f9d2455f4dd04cfca785c70bbfff1a76a3", [:mix], [{:nimble_parsec, "~> 1.2.2 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "cce1566b81fbcbd21eca8ffe808f33b221f9eee2cbc7a1706fc3da9ff18e6cac"},
+  "makeup_elixir": {:hex, :makeup_elixir, "0.16.2", "627e84b8e8bf22e60a2579dad15067c755531fea049ae26ef1020cad58fe9578", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.2.3 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "41193978704763f6bbe6cc2758b84909e62984c7752b3784bd3c218bb341706b"},
+  "makeup_erlang": {:hex, :makeup_erlang, "1.0.1", "c7f58c120b2b5aa5fd80d540a89fdf866ed42f1f3994e4fe189abebeab610839", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "8a89a1eeccc2d798d6ea15496a6e4870b75e014d1af514b1b71fa33134f57814"},
+  "nimble_parsec": {:hex, :nimble_parsec, "1.4.0", "51f9b613ea62cfa97b25ccc2c1b4216e81df970acd8e16e8d1bdc58fef21370d", [:mix], [], "hexpm", "9c565862810fb383e9838c1dd2d7d2c437b3d13b267414ba6af33e50d2d1cf28"},
 }

test/liveness_test.exs

@@ -6,6 +6,8 @@ defmodule LivenessTest do
   test "it returns value immediately if fun neither returns false nor raises" do
     assert eventually(fn -> 123 end) == 123
     assert eventually(fn -> :ok end) == :ok
+    assert eventually(fn -> {:ok, 123} end) == {:ok, 123}
+    assert eventually(fn -> {:ok, 123, 456} end) == {:ok, 123, 456}
     assert eventually(fn -> "foo" end) == "foo"
   end
 
@@ -21,6 +23,24 @@ defmodule LivenessTest do
     end
   end
 
+  test "it raises an exception if fun returns :error" do
+    assert_raise Liveness, "function returned :error", fn ->
+      eventually(fn -> :error end, 2, 20)
+    end
+  end
+
+  test "it raises an exception if fun returns a tuple with :error as the first element" do
+    assert_raise Liveness, ~s(function returned {:error, "Something went wrong"}), fn ->
+      eventually(fn -> {:error, "Something went wrong"} end, 2, 20)
+    end
+
+    assert_raise Liveness,
+                 ~s(function returned {:error, "Something went wrong", :server_error}),
+                 fn ->
+                   eventually(fn -> {:error, "Something went wrong", :server_error} end, 2, 20)
+                 end
+  end
+
   test "it raises an exception that fun raises" do
     assert_raise ArgumentError, "this is an argument error", fn ->
       eventually(fn -> raise(ArgumentError, "this is an argument error") end, 2, 20)