stdlib: Deprecate gen_fsm

6 files changed, 45 insertions, 385 deletions

diff --git a/system/doc/design_principles/fsm.xml b/system/doc/design_principles/fsm.xml
deleted file mode 100644
index 4f2b75e6e8..0000000000
--- a/system/doc/design_principles/fsm.xml
+++ /dev/null
@@ -1,338 +0,0 @@
-<?xml version="1.0" encoding="utf-8" ?>
-<!DOCTYPE chapter SYSTEM "chapter.dtd">
-
-<chapter>
-  <header>
-    <copyright>
-      <year>1997</year><year>2016</year>
-      <holder>Ericsson AB. All Rights Reserved.</holder>
-    </copyright>
-    <legalnotice>
-      Licensed under the Apache License, Version 2.0 (the "License");
-      you may not use this file except in compliance with the License.
-      You may obtain a copy of the License at
- 
-          http://www.apache.org/licenses/LICENSE-2.0
-
-      Unless required by applicable law or agreed to in writing, software
-      distributed under the License is distributed on an "AS IS" BASIS,
-      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-      See the License for the specific language governing permissions and
-      limitations under the License.
-    
-    </legalnotice>
-
-    <title>gen_fsm Behaviour</title>
-    <prepared></prepared>
-    <docno></docno>
-    <date></date>
-    <rev></rev>
-    <file>fsm.xml</file>
-  </header>
-  <marker id="gen_fsm behaviour"></marker>
-    <note>
-      <p>
-	There is a new behaviour
-	<seealso marker="statem"><c>gen_statem</c></seealso>
-	that is intended to replace <c>gen_fsm</c> for new code.
-	It has the same features and add some really useful.
-	This module will not be removed for the foreseeable future
-	to keep old state machine implementations running.
-      </p>
-    </note>
-  <p>This section is to be read with the <c>gen_fsm(3)</c> manual page
-    in STDLIB, where all interface functions and callback
-    functions are described in detail.</p>
-
-  <section>
-    <title>Finite-State Machines</title>
-    <p>A Finite-State Machine (FSM) can be described as a set of
-      relations of the form:</p>
-    <pre>
-State(S) x Event(E) -> Actions(A), State(S')</pre>
-    <p>These relations are interpreted as meaning:</p>
-    <quote>
-      <p>If we are in state <c>S</c> and event <c>E</c> occurs, we
-        are to perform actions <c>A</c> and make a transition to
-        state <c>S'</c>.</p>
-    </quote>
-    <p>For an FSM implemented using the <c>gen_fsm</c> behaviour,
-      the state transition rules are written as a number of Erlang
-      functions, which conform to the following convention:</p>
-    <pre>
-StateName(Event, StateData) ->
-    .. code for actions here ...
-    {next_state, StateName', StateData'}</pre>
-  </section>
-
-  <section>
-    <title>Example</title>
-    <p>A door with a code lock can be viewed as an FSM. Initially,
-      the door is locked. Anytime someone presses a button, this
-      generates an event. Depending on what buttons have been pressed
-      before, the sequence so far can be correct, incomplete, or wrong.</p>
-    <p>If it is correct, the door is unlocked for 30 seconds (30,000 ms).
-      If it is incomplete, we wait for another button to be pressed. If
-      it is is wrong, we start all over, waiting for a new button
-      sequence.</p>
-    <p>Implementing the code lock FSM using <c>gen_fsm</c> results in
-      the following callback module:</p>
-    <marker id="ex"></marker>
-    <code type="none"><![CDATA[
--module(code_lock).
--behaviour(gen_fsm).
-
--export([start_link/1]).
--export([button/1]).
--export([init/1, locked/2, open/2]).
-
-start_link(Code) ->
-    gen_fsm:start_link({local, code_lock}, code_lock, lists:reverse(Code), []).
-
-button(Digit) ->
-    gen_fsm:send_event(code_lock, {button, Digit}).
-
-init(Code) ->
-    {ok, locked, {[], Code}}.
-
-locked({button, Digit}, {SoFar, Code}) ->
-    case [Digit|SoFar] of
-        Code ->
-            do_unlock(),
-            {next_state, open, {[], Code}, 30000};
-        Incomplete when length(Incomplete)<length(Code) ->
-            {next_state, locked, {Incomplete, Code}};
-        _Wrong ->
-            {next_state, locked, {[], Code}}
-    end.
-
-open(timeout, State) ->
-    do_lock(),
-    {next_state, locked, State}.]]></code>
-    <p>The code is explained in the next sections.</p>
-  </section>
-
-  <section>
-    <title>Starting gen_fsm</title>
-    <p>In the example in the previous section, the <c>gen_fsm</c> is
-      started by calling <c>code_lock:start_link(Code)</c>:</p>
-    <code type="none">
-start_link(Code) ->
-    gen_fsm:start_link({local, code_lock}, code_lock, lists:reverse(Code), []).
-    </code>
-    <p><c>start_link</c> calls the function <c>gen_fsm:start_link/4</c>,
-    which spawns and links to a new process, a <c>gen_fsm</c>.</p>
-    <list type="bulleted">
-      <item>
-        <p>The first argument, <c>{local, code_lock}</c>, specifies
-          the name. In this case, the <c>gen_fsm</c> is locally
-	  registered as <c>code_lock</c>.</p>
-        <p>If the name is omitted, the <c>gen_fsm</c> is not registered.
-          Instead its pid must be used. The name can also be given
-	  as <c>{global, Name}</c>, in which case the <c>gen_fsm</c> is
-	  registered using <c>global:register_name/2</c>.</p>
-      </item>
-      <item>
-        <p>The second argument, <c>code_lock</c>, is the name of
-          the callback module, that is, the module where the callback
-          functions are located.</p>
-        <p>The interface functions (<c>start_link</c> and <c>button</c>)
-	  are then located in the same module as the callback
-          functions (<c>init</c>, <c>locked</c>, and <c>open</c>). This
-          is normally good programming practice, to have the code
-          corresponding to one process contained in one module.</p>
-      </item>
-      <item>
-        <p>The third argument, <c>Code</c>, is a list of digits that
-	  which is passed reversed to the callback function <c>init</c>.
-	  Here, <c>init</c>
-          gets the correct code for the lock as indata.</p>
-      </item>
-      <item>
-        <p>The fourth argument, <c>[]</c>, is a list of options. See
-          the <c>gen_fsm(3)</c> manual page for available options.</p>
-      </item>
-    </list>
-    <p>If name registration succeeds, the new <c>gen_fsm</c> process calls
-      the callback function <c>code_lock:init(Code)</c>. This function
-      is expected to return <c>{ok, StateName, StateData}</c>, where
-      <c>StateName</c> is the name of the initial state of the
-      <c>gen_fsm</c>. In this case <c>locked</c>, assuming the door is
-      locked to begin with. <c>StateData</c> is the internal state of
-      the <c>gen_fsm</c>. (For <c>gen_fsm</c>, the internal state is
-      often referred to 'state data' to
-      distinguish it from the state as in states of a state machine.)
-      In this case, the state data is the button sequence so far (empty
-      to begin with) and the correct code of the lock.</p>
-    <code type="none">
-init(Code) ->
-    {ok, locked, {[], Code}}.</code>
-    <p><c>gen_fsm:start_link</c> is synchronous. It does not return until
-    the <c>gen_fsm</c> has been initialized and is ready to
-      receive notifications.</p>
-    <p><c>gen_fsm:start_link</c> must be used if the <c>gen_fsm</c> is
-      part of a supervision tree, that is, started by a supervisor. There
-      is another function, <c>gen_fsm:start</c>, to start a standalone
-      <c>gen_fsm</c>, that is, a <c>gen_fsm</c> that is not part of a
-      supervision tree.</p>
-  </section>
-
-  <section>
-    <title>Notifying about Events</title>
-    <p>The function notifying the code lock about a button event is
-      implemented using <c>gen_fsm:send_event/2</c>:</p>
-    <code type="none">
-button(Digit) ->
-    gen_fsm:send_event(code_lock, {button, Digit}).</code>
-    <p><c>code_lock</c> is the name of the <c>gen_fsm</c> and must
-      agree with the name used to start it.
-      <c>{button, Digit}</c> is the actual event.</p>
-    <p>The event is made into a message and sent to the <c>gen_fsm</c>.
-      When the event is received, the <c>gen_fsm</c> calls
-      <c>StateName(Event, StateData)</c>, which is expected to return a
-      tuple <c>{next_state,StateName1,StateData1}</c>.
-      <c>StateName</c> is the name of the current state and
-      <c>StateName1</c> is the name of the next state to go to.
-      <c>StateData1</c> is a new value for the state data of
-      the <c>gen_fsm</c>.</p>
-    <code type="none"><![CDATA[
-locked({button, Digit}, {SoFar, Code}) ->
-    case [Digit|SoFar] of
-        Code ->
-            do_unlock(),
-            {next_state, open, {[], Code}, 30000};
-        Incomplete when length(Incomplete)<length(Code) ->
-            {next_state, locked, {Incomplete, Code}};
-        _Wrong ->
-            {next_state, locked, {[], Code}};
-    end.
-
-open(timeout, State) ->
-    do_lock(),
-    {next_state, locked, State}.]]></code>
-    <p>If the door is locked and a button is pressed, the complete
-      button sequence so far is compared with the correct code for
-      the lock and, depending on the result, the door is either unlocked
-      and the <c>gen_fsm</c> goes to state <c>open</c>, or the door
-      remains in state <c>locked</c>.</p>
-  </section>
-
-  <section>
-    <title>Time-Outs</title>
-    <p>When a correct code has been given, the door is unlocked and
-      the following tuple is returned from <c>locked/2</c>:</p>
-    <code type="none">
-{next_state, open, {[], Code}, 30000};</code>
-    <p>30,000 is a time-out value in milliseconds. After this time,
-      that is, 30 seconds, a time-out occurs. Then,
-      <c>StateName(timeout, StateData)</c> is called. The time-out
-      then occurs when the door has been in state <c>open</c> for 30
-      seconds. After that the door is locked again:</p>
-    <code type="none">
-open(timeout, State) ->
-    do_lock(),
-    {next_state, locked, State}.</code>
-  </section>
-
-  <section>
-    <title>All State Events</title>
-    <p>Sometimes an event can arrive at any state of the <c>gen_fsm</c>.
-      Instead of sending the message with <c>gen_fsm:send_event/2</c>
-      and writing one clause handling the event for each state function,
-      the message can be sent with <c>gen_fsm:send_all_state_event/2</c>
-      and handled with <c>Module:handle_event/3</c>:</p>
-    <code type="none">
--module(code_lock).
-...
--export([stop/0]).
-...
-
-stop() ->
-    gen_fsm:send_all_state_event(code_lock, stop).
-
-...
-
-handle_event(stop, _StateName, StateData) ->
-    {stop, normal, StateData}.</code>
-  </section>
-
-  <section>
-    <title>Stopping</title>
-
-    <section>
-      <title>In a Supervision Tree</title>
-      <p>If the <c>gen_fsm</c> is part of a supervision tree, no stop
-        function is needed. The <c>gen_fsm</c> is automatically
-	terminated by its supervisor. Exactly how this is done is
-	defined by a
-	<seealso marker="sup_princ#shutdown">shutdown strategy</seealso>
-        set in the supervisor.</p>
-      <p>If it is necessary to clean up before termination, the shutdown
-        strategy must be a time-out value and the <c>gen_fsm</c> must be
-	set to trap exit signals in the <c>init</c> function. When ordered
-        to shutdown, the <c>gen_fsm</c> then calls the callback function
-        <c>terminate(shutdown, StateName, StateData)</c>:</p>
-      <code type="none">
-init(Args) ->
-    ...,
-    process_flag(trap_exit, true),
-    ...,
-    {ok, StateName, StateData}.
-
-...
-
-terminate(shutdown, StateName, StateData) ->
-    ..code for cleaning up here..
-    ok.</code>
-    </section>
-
-    <section>
-      <title>Standalone gen_fsm</title>
-      <p>If the <c>gen_fsm</c> is not part of a supervision tree, a stop
-        function can be useful, for example:</p>
-      <code type="none">
-...
--export([stop/0]).
-...
-
-stop() ->
-    gen_fsm:send_all_state_event(code_lock, stop).
-...
-
-handle_event(stop, _StateName, StateData) ->
-    {stop, normal, StateData}.
-
-...
-
-terminate(normal, _StateName, _StateData) ->
-    ok.</code>
-      <p>The callback function handling the <c>stop</c> event returns a
-        tuple, <c>{stop,normal,StateData1}</c>, where <c>normal</c>
-        specifies that it is a normal termination and <c>StateData1</c>
-        is a new value for the state data of the <c>gen_fsm</c>. This
-        causes the <c>gen_fsm</c> to call
-        <c>terminate(normal,StateName,StateData1)</c> and then
-        it terminates gracefully:</p>
-    </section>
-  </section>
-
-  <section>
-    <title>Handling Other Messages</title>
-    <p>If the <c>gen_fsm</c> is to be able to receive other messages
-      than events, the callback function
-      <c>handle_info(Info, StateName, StateData)</c> must be implemented
-      to handle them. Examples of
-      other messages are exit messages, if the <c>gen_fsm</c> is linked to
-      other processes (than the supervisor) and trapping exit signals.</p>
-    <code type="none">
-handle_info({'EXIT', Pid, Reason}, StateName, StateData) ->
-    ..code to handle exits here..
-    {next_state, StateName1, StateData1}.</code>
-    <p>The code_change method must also be implemented.</p>
-    <code type="none">
-code_change(OldVsn, StateName, StateData, Extra) ->
-    ..code to convert state (and more) during code change
-    {ok, NextStateName, NewStateData}</code>
-  </section>
-</chapter>
-
diff --git a/system/doc/design_principles/part.xml b/system/doc/design_principles/part.xml
index 6495211e04..d52070a674 100644
--- a/system/doc/design_principles/part.xml
+++ b/system/doc/design_principles/part.xml
@@ -30,7 +30,6 @@
   </header>
   <xi:include href="des_princ.xml"/>
   <xi:include href="gen_server_concepts.xml"/>
-  <xi:include href="fsm.xml"/>
   <xi:include href="statem.xml"/>
   <xi:include href="events.xml"/>
   <xi:include href="sup_princ.xml"/>
diff --git a/system/doc/design_principles/spec_proc.xml b/system/doc/design_principles/spec_proc.xml
index 5b156ac263..d663c5df79 100644
--- a/system/doc/design_principles/spec_proc.xml
+++ b/system/doc/design_principles/spec_proc.xml
@@ -45,61 +45,63 @@
     <p>The <c>sys</c> module has functions for simple debugging of
     processes implemented using behaviours. The <c>code_lock</c>
     example from
-    <seealso marker="fsm#ex">gen_fsm Behaviour</seealso>
+    <seealso marker="statem#Example">gen_statem Behaviour</seealso>
     is used to illustrate this:</p>
     <pre>
-% <input>erl</input>
-Erlang (BEAM) emulator version 5.2.3.6 [hipe] [threads:0]
+Erlang/OTP 20 [DEVELOPMENT] [erts-9.0] [source-5ace45e] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:10] [hipe] [kernel-poll:false]
 
-Eshell V5.2.3.6  (abort with ^G)
-1> <input>code_lock:start_link([1,2,3,4]).</input>
-{ok,&lt;0.32.0>}
-2> <input>sys:statistics(code_lock, true).</input>
+Eshell V9.0  (abort with ^G)
+1>  code_lock:start_link([1,2,3,4]).
+Lock
+{ok,&lt;0.63.0>}
+2> sys:statistics(code_lock, true).
 ok
-3> <input>sys:trace(code_lock, true).</input>
+3>  sys:trace(code_lock, true).
 ok
-4> <input>code_lock:button(4).</input>
-*DBG* code_lock got event {button,4} in state closed
+4>  code_lock:button(1).
+*DBG* code_lock receive cast {button,1} in state locked
 ok
-*DBG* code_lock switched to state closed
-5> <input>code_lock:button(3).</input>
-*DBG* code_lock got event {button,3} in state closed
+*DBG* code_lock consume cast {button,1} in state locked
+5>  code_lock:button(2).
+*DBG* code_lock receive cast {button,2} in state locked
 ok
-*DBG* code_lock switched to state closed
-6> <input>code_lock:button(2).</input>
-*DBG* code_lock got event {button,2} in state closed
+*DBG* code_lock consume cast {button,2} in state locked
+6>  code_lock:button(3).
+*DBG* code_lock receive cast {button,3} in state locked
 ok
-*DBG* code_lock switched to state closed
-7> <input>code_lock:button(1).</input>
-*DBG* code_lock got event {button,1} in state closed
+*DBG* code_lock consume cast {button,3} in state locked
+7>  code_lock:button(4).
+*DBG* code_lock receive cast {button,4} in state locked
 ok
-OPEN DOOR
-*DBG* code_lock switched to state open
-*DBG* code_lock got event timeout in state open
-CLOSE DOOR
-*DBG* code_lock switched to state closed
-8> <input>sys:statistics(code_lock, get).</input> 
-{ok,[{start_time,{{2003,6,12},{14,11,40}}},
-     {current_time,{{2003,6,12},{14,12,14}}},
-     {reductions,333},
+Unlock
+*DBG* code_lock consume cast {button,4} in state locked
+*DBG* code_lock receive state_timeout lock in state open
+Lock
+*DBG* code_lock consume state_timeout lock in state open
+8> sys:statistics(code_lock, get).
+{ok,[{start_time,{{2017,4,21},{16,8,7}}},
+     {current_time,{{2017,4,21},{16,9,42}}},
+     {reductions,2973},
      {messages_in,5},
      {messages_out,0}]}
-9> <input>sys:statistics(code_lock, false).</input>
+9> sys:statistics(code_lock, false).
 ok
-10> <input>sys:trace(code_lock, false).</input>     
+10> sys:trace(code_lock, false).
 ok
-11> <input>sys:get_status(code_lock).</input>
-{status,&lt;0.32.0>,
-        {module,gen_fsm},
-        [[{'$ancestors',[&lt;0.30.0>]},
-          {'$initial_call',{gen,init_it,
-                                [gen_fsm,&lt;0.30.0>,&lt;0.30.0>,
-                                 {local,code_lock},
-                                 code_lock,
-                                 [1,2,3,4],
-                                 []]}}],
-         running,&lt;0.30.0>,[],
-         [code_lock,closed,{[],[1,2,3,4]},code_lock,infinity]]}</pre>
+11> sys:get_status(code_lock).
+{status,&lt;0.63.0>,
+        {module,gen_statem},
+        [[{'$initial_call',{code_lock,init,1}},
+          {'$ancestors',[&lt;0.61.0>]}],
+         running,&lt;0.61.0>,[],
+         [{header,"Status for state machine code_lock"},
+          {data,[{"Status",running},
+                 {"Parent",&lt;0.61.0>},
+                 {"Logged Events",[]},
+                 {"Postponed",[]}]},
+          {data,[{"State",
+                  {locked,#{code => [1,2,3,4],remaining => [1,2,3,4]}}}]}]]}
+    </pre>
   </section>
 
   <section>
diff --git a/system/doc/design_principles/sup_princ.xml b/system/doc/design_principles/sup_princ.xml
index 478d1bf714..4fd210aa48 100644
--- a/system/doc/design_principles/sup_princ.xml
+++ b/system/doc/design_principles/sup_princ.xml
@@ -276,7 +276,6 @@ child_spec() = #{id => child_id(),       % mandatory
 	<list type="bulleted">
 	  <item><c>supervisor:start_link</c></item>
 	  <item><c>gen_server:start_link</c></item>
-	  <item><c>gen_fsm:start_link</c></item>
 	  <item><c>gen_statem:start_link</c></item>
 	  <item><c>gen_event:start_link</c></item>
 	  <item>A function compliant with these functions. For details,
@@ -341,7 +340,7 @@ child_spec() = #{id => child_id(),       % mandatory
         <p><c>modules</c> are to be a list with one element
           <c>[Module]</c>, where <c>Module</c> is the name of
           the callback module, if the child process is a supervisor,
-          gen_server, gen_fsm or gen_statem.
+          gen_server, gen_statem.
 	  If the child process is a gen_event,
           the value shall be <c>dynamic</c>.</p>
         <p>This information is used by the release handler during
diff --git a/system/doc/design_principles/xmlfiles.mk b/system/doc/design_principles/xmlfiles.mk
index e476255d62..8877e94f39 100644
--- a/system/doc/design_principles/xmlfiles.mk
+++ b/system/doc/design_principles/xmlfiles.mk
@@ -24,7 +24,6 @@ DESIGN_PRINCIPLES_CHAPTER_FILES = \
 	des_princ.xml \
 	distributed_applications.xml \
 	events.xml \
-	fsm.xml \
 	statem.xml \
 	gen_server_concepts.xml \
 	included_applications.xml \
diff --git a/system/doc/reference_manual/modules.xml b/system/doc/reference_manual/modules.xml
index 96968b547e..6fe6680c84 100644
--- a/system/doc/reference_manual/modules.xml
+++ b/system/doc/reference_manual/modules.xml
@@ -143,7 +143,6 @@ fact(0) ->           %  |
         standard behaviours:</p>
 	<list type="bulleted">
 	  <item><c>gen_server</c></item>
-	  <item><c>gen_fsm</c></item>
 	  <item><c>gen_statem</c></item>
 	  <item><c>gen_event</c></item>
 	  <item><c>supervisor</c></item>