diff --git a/LICENSE b/LICENSE
new file mode 100644
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,30 @@
+Copyright (c) 2016, Google Inc.
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of Google Inc. nor the names of other
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/Setup.hs b/Setup.hs
new file mode 100644
--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,9 @@
+-- Copyright 2016 Google Inc. All Rights Reserved.
+--
+-- Use of this source code is governed by a BSD-style
+-- license that can be found in the LICENSE file or at
+-- https://developers.google.com/open-source/licenses/bsd
+
+import Data.ProtoLens.Setup
+
+main = defaultMainGeneratingProtos "tests"
diff --git a/dist/build/autogen/Proto/Combinators.hs b/dist/build/autogen/Proto/Combinators.hs
new file mode 100644
--- /dev/null
+++ b/dist/build/autogen/Proto/Combinators.hs
@@ -0,0 +1,277 @@
+{- This file was auto-generated from combinators.proto by the proto-lens-protoc program. -}
+{-# LANGUAGE ScopedTypeVariables, DataKinds, TypeFamilies,
+  MultiParamTypeClasses, FlexibleContexts, FlexibleInstances #-}
+{-# OPTIONS_GHC -fno-warn-unused-imports#-}
+module Proto.Combinators where
+import qualified Prelude
+import qualified Data.ProtoLens
+import qualified Data.ProtoLens.Message.Enum
+import qualified Lens.Family2
+import qualified Lens.Family2.Unchecked
+import qualified Data.Default.Class
+import qualified Data.Text
+import qualified Data.Int
+import qualified Data.Word
+import qualified Data.Map
+import qualified Data.ByteString
+
+data Foo = Foo{_Foo'quux :: Prelude.Maybe Data.Int.Int32,
+               _Foo'foo :: Prelude.Maybe Foo'Bar,
+               _Foo'bar :: Prelude.Maybe Foo'Bar,
+               _Foo'baz :: Prelude.Maybe Foo'Bar}
+         deriving (Prelude.Show, Prelude.Eq)
+
+type instance Data.ProtoLens.Field "quux" Foo = Data.Int.Int32
+
+instance Data.ProtoLens.HasField "quux" Foo Foo where
+        field _
+          = (Prelude..) maybe'quux
+              (Data.ProtoLens.maybeLens Data.ProtoLens.fieldDefault)
+
+type instance Data.ProtoLens.Field "maybe'quux" Foo =
+     Prelude.Maybe Data.Int.Int32
+
+instance Data.ProtoLens.HasField "maybe'quux" Foo Foo where
+        field _
+          = Lens.Family2.Unchecked.lens _Foo'quux
+              (\ x__ y__ -> x__{_Foo'quux = y__})
+
+type instance Data.ProtoLens.Field "foo" Foo = Foo'Bar
+
+instance Data.ProtoLens.HasField "foo" Foo Foo where
+        field _
+          = (Prelude..) maybe'foo
+              (Data.ProtoLens.maybeLens Data.Default.Class.def)
+
+type instance Data.ProtoLens.Field "maybe'foo" Foo =
+     Prelude.Maybe Foo'Bar
+
+instance Data.ProtoLens.HasField "maybe'foo" Foo Foo where
+        field _
+          = Lens.Family2.Unchecked.lens _Foo'foo
+              (\ x__ y__ -> x__{_Foo'foo = y__})
+
+type instance Data.ProtoLens.Field "bar" Foo = Foo'Bar
+
+instance Data.ProtoLens.HasField "bar" Foo Foo where
+        field _
+          = (Prelude..) maybe'bar
+              (Data.ProtoLens.maybeLens Data.Default.Class.def)
+
+type instance Data.ProtoLens.Field "maybe'bar" Foo =
+     Prelude.Maybe Foo'Bar
+
+instance Data.ProtoLens.HasField "maybe'bar" Foo Foo where
+        field _
+          = Lens.Family2.Unchecked.lens _Foo'bar
+              (\ x__ y__ -> x__{_Foo'bar = y__})
+
+type instance Data.ProtoLens.Field "baz" Foo = Foo'Bar
+
+instance Data.ProtoLens.HasField "baz" Foo Foo where
+        field _
+          = (Prelude..) maybe'baz
+              (Data.ProtoLens.maybeLens Data.Default.Class.def)
+
+type instance Data.ProtoLens.Field "maybe'baz" Foo =
+     Prelude.Maybe Foo'Bar
+
+instance Data.ProtoLens.HasField "maybe'baz" Foo Foo where
+        field _
+          = Lens.Family2.Unchecked.lens _Foo'baz
+              (\ x__ y__ -> x__{_Foo'baz = y__})
+
+instance Data.Default.Class.Default Foo where
+        def
+          = Foo{_Foo'quux = Prelude.Nothing, _Foo'foo = Prelude.Nothing,
+                _Foo'bar = Prelude.Nothing, _Foo'baz = Prelude.Nothing}
+
+instance Data.ProtoLens.Message Foo where
+        descriptor
+          = let quux__field_descriptor
+                  = Data.ProtoLens.FieldDescriptor "quux"
+                      (Data.ProtoLens.Int32Field ::
+                         Data.ProtoLens.FieldTypeDescriptor Data.Int.Int32)
+                      (Data.ProtoLens.OptionalField maybe'quux)
+                foo__field_descriptor
+                  = Data.ProtoLens.FieldDescriptor "foo"
+                      (Data.ProtoLens.MessageField ::
+                         Data.ProtoLens.FieldTypeDescriptor Foo'Bar)
+                      (Data.ProtoLens.OptionalField maybe'foo)
+                bar__field_descriptor
+                  = Data.ProtoLens.FieldDescriptor "bar"
+                      (Data.ProtoLens.MessageField ::
+                         Data.ProtoLens.FieldTypeDescriptor Foo'Bar)
+                      (Data.ProtoLens.OptionalField maybe'bar)
+                baz__field_descriptor
+                  = Data.ProtoLens.FieldDescriptor "baz"
+                      (Data.ProtoLens.MessageField ::
+                         Data.ProtoLens.FieldTypeDescriptor Foo'Bar)
+                      (Data.ProtoLens.OptionalField maybe'baz)
+              in
+              Data.ProtoLens.MessageDescriptor
+                (Data.Map.fromList
+                   [(Data.ProtoLens.Tag 1, quux__field_descriptor),
+                    (Data.ProtoLens.Tag 2, foo__field_descriptor),
+                    (Data.ProtoLens.Tag 3, bar__field_descriptor),
+                    (Data.ProtoLens.Tag 4, baz__field_descriptor)])
+                (Data.Map.fromList
+                   [("quux", quux__field_descriptor), ("foo", foo__field_descriptor),
+                    ("bar", bar__field_descriptor), ("baz", baz__field_descriptor)])
+
+data Foo'Bar = Foo'Bar{_Foo'Bar'fizz ::
+                       Prelude.Maybe Data.Int.Int32,
+                       _Foo'Bar'buzz :: Prelude.Maybe Data.Text.Text}
+             deriving (Prelude.Show, Prelude.Eq)
+
+type instance Data.ProtoLens.Field "fizz" Foo'Bar = Data.Int.Int32
+
+instance Data.ProtoLens.HasField "fizz" Foo'Bar Foo'Bar where
+        field _
+          = (Prelude..) maybe'fizz
+              (Data.ProtoLens.maybeLens Data.ProtoLens.fieldDefault)
+
+type instance Data.ProtoLens.Field "maybe'fizz" Foo'Bar =
+     Prelude.Maybe Data.Int.Int32
+
+instance Data.ProtoLens.HasField "maybe'fizz" Foo'Bar Foo'Bar where
+        field _
+          = Lens.Family2.Unchecked.lens _Foo'Bar'fizz
+              (\ x__ y__ -> x__{_Foo'Bar'fizz = y__})
+
+type instance Data.ProtoLens.Field "buzz" Foo'Bar = Data.Text.Text
+
+instance Data.ProtoLens.HasField "buzz" Foo'Bar Foo'Bar where
+        field _
+          = (Prelude..) maybe'buzz
+              (Data.ProtoLens.maybeLens Data.ProtoLens.fieldDefault)
+
+type instance Data.ProtoLens.Field "maybe'buzz" Foo'Bar =
+     Prelude.Maybe Data.Text.Text
+
+instance Data.ProtoLens.HasField "maybe'buzz" Foo'Bar Foo'Bar where
+        field _
+          = Lens.Family2.Unchecked.lens _Foo'Bar'buzz
+              (\ x__ y__ -> x__{_Foo'Bar'buzz = y__})
+
+instance Data.Default.Class.Default Foo'Bar where
+        def
+          = Foo'Bar{_Foo'Bar'fizz = Prelude.Nothing,
+                    _Foo'Bar'buzz = Prelude.Nothing}
+
+instance Data.ProtoLens.Message Foo'Bar where
+        descriptor
+          = let fizz__field_descriptor
+                  = Data.ProtoLens.FieldDescriptor "fizz"
+                      (Data.ProtoLens.Int32Field ::
+                         Data.ProtoLens.FieldTypeDescriptor Data.Int.Int32)
+                      (Data.ProtoLens.OptionalField maybe'fizz)
+                buzz__field_descriptor
+                  = Data.ProtoLens.FieldDescriptor "buzz"
+                      (Data.ProtoLens.StringField ::
+                         Data.ProtoLens.FieldTypeDescriptor Data.Text.Text)
+                      (Data.ProtoLens.OptionalField maybe'buzz)
+              in
+              Data.ProtoLens.MessageDescriptor
+                (Data.Map.fromList
+                   [(Data.ProtoLens.Tag 1, fizz__field_descriptor),
+                    (Data.ProtoLens.Tag 2, buzz__field_descriptor)])
+                (Data.Map.fromList
+                   [("fizz", fizz__field_descriptor),
+                    ("buzz", buzz__field_descriptor)])
+
+bar ::
+    forall msg msg' . Data.ProtoLens.HasField "bar" msg msg' =>
+      Lens.Family2.Lens msg msg' (Data.ProtoLens.Field "bar" msg)
+        (Data.ProtoLens.Field "bar" msg')
+bar
+  = Data.ProtoLens.field
+      (Data.ProtoLens.ProxySym :: Data.ProtoLens.ProxySym "bar")
+
+baz ::
+    forall msg msg' . Data.ProtoLens.HasField "baz" msg msg' =>
+      Lens.Family2.Lens msg msg' (Data.ProtoLens.Field "baz" msg)
+        (Data.ProtoLens.Field "baz" msg')
+baz
+  = Data.ProtoLens.field
+      (Data.ProtoLens.ProxySym :: Data.ProtoLens.ProxySym "baz")
+
+buzz ::
+     forall msg msg' . Data.ProtoLens.HasField "buzz" msg msg' =>
+       Lens.Family2.Lens msg msg' (Data.ProtoLens.Field "buzz" msg)
+         (Data.ProtoLens.Field "buzz" msg')
+buzz
+  = Data.ProtoLens.field
+      (Data.ProtoLens.ProxySym :: Data.ProtoLens.ProxySym "buzz")
+
+fizz ::
+     forall msg msg' . Data.ProtoLens.HasField "fizz" msg msg' =>
+       Lens.Family2.Lens msg msg' (Data.ProtoLens.Field "fizz" msg)
+         (Data.ProtoLens.Field "fizz" msg')
+fizz
+  = Data.ProtoLens.field
+      (Data.ProtoLens.ProxySym :: Data.ProtoLens.ProxySym "fizz")
+
+foo ::
+    forall msg msg' . Data.ProtoLens.HasField "foo" msg msg' =>
+      Lens.Family2.Lens msg msg' (Data.ProtoLens.Field "foo" msg)
+        (Data.ProtoLens.Field "foo" msg')
+foo
+  = Data.ProtoLens.field
+      (Data.ProtoLens.ProxySym :: Data.ProtoLens.ProxySym "foo")
+
+maybe'bar ::
+          forall msg msg' . Data.ProtoLens.HasField "maybe'bar" msg msg' =>
+            Lens.Family2.Lens msg msg' (Data.ProtoLens.Field "maybe'bar" msg)
+              (Data.ProtoLens.Field "maybe'bar" msg')
+maybe'bar
+  = Data.ProtoLens.field
+      (Data.ProtoLens.ProxySym :: Data.ProtoLens.ProxySym "maybe'bar")
+
+maybe'baz ::
+          forall msg msg' . Data.ProtoLens.HasField "maybe'baz" msg msg' =>
+            Lens.Family2.Lens msg msg' (Data.ProtoLens.Field "maybe'baz" msg)
+              (Data.ProtoLens.Field "maybe'baz" msg')
+maybe'baz
+  = Data.ProtoLens.field
+      (Data.ProtoLens.ProxySym :: Data.ProtoLens.ProxySym "maybe'baz")
+
+maybe'buzz ::
+           forall msg msg' . Data.ProtoLens.HasField "maybe'buzz" msg msg' =>
+             Lens.Family2.Lens msg msg' (Data.ProtoLens.Field "maybe'buzz" msg)
+               (Data.ProtoLens.Field "maybe'buzz" msg')
+maybe'buzz
+  = Data.ProtoLens.field
+      (Data.ProtoLens.ProxySym :: Data.ProtoLens.ProxySym "maybe'buzz")
+
+maybe'fizz ::
+           forall msg msg' . Data.ProtoLens.HasField "maybe'fizz" msg msg' =>
+             Lens.Family2.Lens msg msg' (Data.ProtoLens.Field "maybe'fizz" msg)
+               (Data.ProtoLens.Field "maybe'fizz" msg')
+maybe'fizz
+  = Data.ProtoLens.field
+      (Data.ProtoLens.ProxySym :: Data.ProtoLens.ProxySym "maybe'fizz")
+
+maybe'foo ::
+          forall msg msg' . Data.ProtoLens.HasField "maybe'foo" msg msg' =>
+            Lens.Family2.Lens msg msg' (Data.ProtoLens.Field "maybe'foo" msg)
+              (Data.ProtoLens.Field "maybe'foo" msg')
+maybe'foo
+  = Data.ProtoLens.field
+      (Data.ProtoLens.ProxySym :: Data.ProtoLens.ProxySym "maybe'foo")
+
+maybe'quux ::
+           forall msg msg' . Data.ProtoLens.HasField "maybe'quux" msg msg' =>
+             Lens.Family2.Lens msg msg' (Data.ProtoLens.Field "maybe'quux" msg)
+               (Data.ProtoLens.Field "maybe'quux" msg')
+maybe'quux
+  = Data.ProtoLens.field
+      (Data.ProtoLens.ProxySym :: Data.ProtoLens.ProxySym "maybe'quux")
+
+quux ::
+     forall msg msg' . Data.ProtoLens.HasField "quux" msg msg' =>
+       Lens.Family2.Lens msg msg' (Data.ProtoLens.Field "quux" msg)
+         (Data.ProtoLens.Field "quux" msg')
+quux
+  = Data.ProtoLens.field
+      (Data.ProtoLens.ProxySym :: Data.ProtoLens.ProxySym "quux")
diff --git a/proto-lens-combinators.cabal b/proto-lens-combinators.cabal
new file mode 100644
--- /dev/null
+++ b/proto-lens-combinators.cabal
@@ -0,0 +1,42 @@
+name:                proto-lens-combinators
+version:             0.1.0.0
+synopsis:            Utilities functions to proto-lens.
+description:
+  Useful things for working with protos.
+
+homepage:            https://github.com/google/proto-lens
+license:             BSD3
+license-file:        LICENSE
+author:              Zie Weaver
+maintainer:          zearen+protolens@google.com
+copyright:           Google Inc.
+category:            Data
+build-type:          Custom
+cabal-version:       >=1.10
+extra-source-files:  tests/combinators.proto
+
+library
+  default-language: Haskell2010
+  hs-source-dirs: src
+  exposed-modules:     Data.ProtoLens.Combinators
+  build-depends:  proto-lens == 0.1.*
+                -- Used by the custom Setup script (for the test-suite).
+                , proto-lens-protoc == 0.1.*
+                , base == 4.8.*
+                , data-default-class == 0.0.*
+                , lens-family == 1.2.*
+                , transformers == 0.4.*
+
+Test-Suite combinators_test
+  default-language: Haskell2010
+  type: exitcode-stdio-1.0
+  main-is: combinators_test.hs
+  hs-source-dirs: tests
+  other-modules: Proto.Combinators
+  build-depends: HUnit
+               , base
+               , lens-family
+               , proto-lens-combinators
+               , proto-lens-protoc
+               , test-framework
+               , test-framework-hunit
diff --git a/src/Data/ProtoLens/Combinators.hs b/src/Data/ProtoLens/Combinators.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/ProtoLens/Combinators.hs
@@ -0,0 +1,47 @@
+-- Copyright 2016 Google Inc. All Rights Reserved.
+--
+-- Use of this source code is governed by a BSD-style
+-- license that can be found in the LICENSE file or at
+-- https://developers.google.com/open-source/licenses/bsd
+
+{-# LANGUAGE RankNTypes #-}
+-- | An assorted collection of functions useful when working with ProtoLens
+-- protocol buffers.  These functions are inspired by functionality found in
+-- the protobuf implementation in other languages.
+module Data.ProtoLens.Combinators
+    ( has
+    , clear
+    , make
+    , modifyInState
+    ) where
+
+import Control.Monad.Trans.State (State, execState)
+import Data.Default.Class (Default(def))
+import Data.Maybe (isJust)
+import Lens.Family2 (LensLike, Phantom, Setter, to, (.~))
+
+-- | Turns a 'LensLike' getting a 'Maybe' into a 'Getter' of a 'Bool'
+-- that returns @True@ when the 'Maybe' is @Just@ something.
+--
+-- I.e., makes a getter for a 'Maybe' field that returns whether it's set.
+has :: Phantom f => LensLike f a a' (Maybe b) b' -> LensLike f a a' Bool b''
+has = (. to isJust)
+
+-- | Sets the provided lens in @a@ to @Nothing@.
+clear :: Setter a a' b (Maybe b') -> a -> a'
+clear = (.~ Nothing)
+
+-- | Creates a 'Default' and then applies the provided `State` to it.  This is
+-- convenient for creating complicated structures.
+make :: Default def => State def a -> def
+make = modifyInState def
+
+-- | Allows one to modify a value in the 'State' monad.  Note that this is
+-- just for syntactic convenience with @do@ blocks, e.g.
+--
+-- @
+--    newThing = modifyInState thing $ do
+--        ...
+-- @
+modifyInState :: s -> State s a -> s
+modifyInState = flip execState
diff --git a/tests/combinators.proto b/tests/combinators.proto
new file mode 100644
--- /dev/null
+++ b/tests/combinators.proto
@@ -0,0 +1,16 @@
+syntax = "proto2";
+
+package combinators;
+
+message Foo {
+  optional int32 quux = 1;
+
+  message Bar {
+    optional int32 fizz = 1;
+    optional string buzz = 2;
+  }
+
+  optional Bar foo = 2;
+  optional Bar bar = 3;
+  optional Bar baz = 4;
+}
diff --git a/tests/combinators_test.hs b/tests/combinators_test.hs
new file mode 100644
--- /dev/null
+++ b/tests/combinators_test.hs
@@ -0,0 +1,55 @@
+-- Copyright 2016 Google Inc. All Rights Reserved.
+--
+-- Use of this source code is governed by a BSD-style
+-- license that can be found in the LICENSE file or at
+-- https://developers.google.com/open-source/licenses/bsd
+
+{-# LANGUAGE OverloadedStrings #-}
+module Main where
+
+import Data.ProtoLens (def)
+import Data.ProtoLens.Combinators
+import Lens.Family2 ((^.), (.~), (&))
+import Lens.Family2.State ((.=), (<~), use, zoom)
+import Proto.Combinators
+import Test.Framework (defaultMain)
+import Test.Framework.Providers.HUnit (hUnitTestToTests)
+import Test.HUnit ((~:), (~?=))
+
+main :: IO ()
+main = defaultMain $ hUnitTestToTests $ "" ~:
+    [ let proto = def & quux .~ 1 & foo .~ def :: Foo
+      in "has" ~:
+          [ "True" ~: proto ^. has maybe'quux ~?= True
+          , "False" ~: proto ^. has maybe'bar ~?= False
+          , "Nested" ~:
+              [ "True" ~: proto ^. has maybe'foo ~?= True
+              , "False" ~: proto ^. has (foo . maybe'buzz) ~?= False
+              ]
+          ]
+    , let proto = def & quux .~ 2 & foo . fizz .~ 3 :: Foo
+      in "clear" ~:
+          [ "no-op" ~: clear maybe'bar proto ~?= proto
+          , "scalar" ~: clear maybe'quux proto ~?= (def & foo . fizz .~ 3)
+          , "group" ~: clear maybe'foo proto ~?= (def & quux .~ 2)
+          , "nested" ~: clear (foo . maybe'fizz) proto ~?=
+              (def & quux .~ 2 & foo .~ def)
+          ]
+    , let actual :: Foo
+          actual = make $ do
+              quux .= 4
+              foo . buzz .= "A"
+              zoom bar $ do
+                  fizz .= 5
+                  buzz .= "B"
+              zoom baz $ return ()
+          expected = def & quux .~ 4 & foo . buzz .~ "A" &
+              bar .~ (def & fizz .~ 5 & buzz .~ "B") & baz .~ def
+      in "make" ~: actual ~?= expected
+    , let original = def & quux .~ 6 & baz . fizz .~ 7 :: Foo
+          actual = modifyInState original $ do
+              bar . fizz <~ use quux
+              quux .= 8
+          expected = def & quux .~ 8 & bar . fizz .~ 6 & baz . fizz .~ 7
+      in "modifyInState" ~: actual ~?= expected
+    ]