Merge branch 'saa/add_default_value_for_maps_get/OTP-11951' into maint

* saa/add_default_value_for_maps_get/OTP-11951:
  stdlib: Fix indentation of maps doc
  Add docs and test for maps:get/3
  Add default value for maps:get

4 files changed, 108 insertions, 2 deletions

diff --git a/lib/stdlib/doc/src/maps.xml b/lib/stdlib/doc/src/maps.xml
index 76137e3dee..b37f7fd7fd 100644
--- a/lib/stdlib/doc/src/maps.xml
+++ b/lib/stdlib/doc/src/maps.xml
@@ -108,6 +108,26 @@
 		</func>
 
 		<func>
+			<name name="get" arity="3"/>
+			<fsummary></fsummary>
+			<desc>
+				<p>
+					Returns the value <c><anno>Value</anno></c> associated with <c><anno>Key</anno></c> if
+					<c><anno>Map</anno></c> contains <c><anno>Key</anno></c>.
+					If no value is associated with <c><anno>Key</anno></c> then returns <c><anno>Default</anno></c>.
+				</p>
+				<p>Example:</p>
+				<code type="none">
+> Map = #{ key1 => val1, key2 => val2 }.
+#{key1 => val1,key2 => val2}
+> maps:get(key1, Map, "Default value").
+val1
+> maps:get(key3, Map, "Default value").
+"Default value"</code>
+			</desc>
+		</func>
+
+		<func>
 			<name name="is_key" arity="2"/>
 			<fsummary></fsummary>
 			<desc>
diff --git a/lib/stdlib/src/maps.erl b/lib/stdlib/src/maps.erl
index fd6d56fa47..4ef1638e6d 100644
--- a/lib/stdlib/src/maps.erl
+++ b/lib/stdlib/src/maps.erl
@@ -23,7 +23,8 @@
 	fold/3,
 	map/2,
 	size/1,
-	without/2
+    without/2,
+    get/3
     ]).
 
 
@@ -142,6 +143,21 @@ values(_) -> erlang:nif_error(undef).
 
 %%% End of BIFs
 
+-spec get(Key, Map, Default) -> Value | Default when
+        Key :: term(),
+        Map :: map(),
+        Value :: term(),
+        Default :: term().
+
+get(Key, Map, Default) ->
+    case maps:find(Key, Map) of
+        {ok, Value} ->
+            Value;
+        error ->
+            Default
+    end.
+
+
 -spec fold(Fun,Init,Map) -> Acc when
     Fun :: fun((K, V, AccIn) -> AccOut),
     Init :: term(),
diff --git a/lib/stdlib/test/Makefile b/lib/stdlib/test/Makefile
index 39f6ce423a..a271229c59 100644
--- a/lib/stdlib/test/Makefile
+++ b/lib/stdlib/test/Makefile
@@ -85,7 +85,8 @@ MODULES= \
 	zip_SUITE \
 	random_unicode_list \
 	random_iolist \
-	error_logger_forwarder
+	error_logger_forwarder \
+	maps_SUITE
 
 ERL_FILES= $(MODULES:%=%.erl)
 
diff --git a/lib/stdlib/test/maps_SUITE.erl b/lib/stdlib/test/maps_SUITE.erl
new file mode 100644
index 0000000000..c826ee731a
--- /dev/null
+++ b/lib/stdlib/test/maps_SUITE.erl
@@ -0,0 +1,69 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 1997-2014. All Rights Reserved.
+%%
+%% The contents of this file are subject to the Erlang Public License,
+%% Version 1.1, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Erlang Public License along with this software. If not, it can be
+%% retrieved online at http://www.erlang.org/.
+%%
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%%
+%% %CopyrightEnd%
+%%
+%%%----------------------------------------------------------------
+%%% Purpose: Test suite for the 'maps' module.
+%%%-----------------------------------------------------------------
+
+-module(maps_SUITE).
+
+-include_lib("test_server/include/test_server.hrl").
+
+% Default timetrap timeout (set in init_per_testcase).
+% This should be set relatively high (10-15 times the expected
+% max testcasetime).
+-define(default_timeout, ?t:minutes(4)).
+
+% Test server specific exports
+-export([all/0]).
+-export([suite/0]).
+-export([init_per_suite/1]).
+-export([end_per_suite/1]).
+-export([init_per_testcase/2]).
+-export([end_per_testcase/2]).
+
+-export([get3/1]).
+
+suite() ->
+    [{ct_hooks, [ts_install_cth]}].
+
+all() ->
+    [get3].
+
+init_per_suite(Config) ->
+    Config.
+
+end_per_suite(_Config) ->
+    ok.
+
+init_per_testcase(_Case, Config) ->
+    ?line Dog=test_server:timetrap(?default_timeout),
+    [{watchdog, Dog}|Config].
+
+end_per_testcase(_Case, Config) ->
+    Dog=?config(watchdog, Config),
+    test_server:timetrap_cancel(Dog),
+    ok.
+
+get3(Config) when is_list(Config) ->
+    Map = #{ key1 => value1, key2 => value2 },
+    DefaultValue = "Default value",
+    ?line value1 = maps:get(key1, Map, DefaultValue),
+    ?line value2 = maps:get(key2, Map, DefaultValue),
+    ?line DefaultValue = maps:get(key3, Map, DefaultValue),
+    ok.