patch 8.0.0105v8.0.0105

Problem:    When using ch_read() with zero timeout, can't tell the difference
            between reading an empty line and nothing available.
Solution:   Add ch_canread().

8 files changed, 65 insertions, 14 deletions

diff --git a/runtime/doc/channel.txt b/runtime/doc/channel.txt
index 73105986f6..2c3f837300 100644
--- a/runtime/doc/channel.txt
+++ b/runtime/doc/channel.txt
@@ -418,7 +418,11 @@ This uses the channel timeout.  To read without a timeout, just get any
 message that is available: >
 	let output = ch_read(channel, {'timeout': 0})
 When no message was available then the result is v:none for a JSON or JS mode
-channels, an empty string for a RAW or NL channel.
+channels, an empty string for a RAW or NL channel.  You can use |ch_canread()|
+to check if there is something to read.
+
+Note that when there is no callback message are dropped.  To avoid that add a
+close callback to the channel.
 
 To read all output from a RAW channel that is available: >
 	let output = ch_readraw(channel)
@@ -470,6 +474,11 @@ This depends on the system (on Unix this happens because closing the write end
 of a pipe causes the read end to get EOF).  To avoid this make the job sleep
 for a short while before it exits.
 
+Note that if the job exits before you read the output, the output may be lost.
+This depends on the system (on Unix this happens because closing the write end
+of a pipe causes the read end to get EOF).  To avoid this make the job sleep
+for a short while before it exits.
+
 The handler defined for "out_cb" will not receive stderr.  If you want to
 handle that separately, add an "err_cb" handler: >
     let job = job_start(command, {"out_cb": "MyHandler",
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 1a11a41411..75c2ea1132 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -2009,6 +2009,7 @@ byteidxcomp({expr}, {nr})	Number	byte index of {nr}'th char in {expr}
 call({func}, {arglist} [, {dict}])
 				any	call {func} with arguments {arglist}
 ceil({expr})			Float	round {expr} up
+ch_canread({handle})		Number	check if there is something to read
 ch_close({handle})		none	close {handle}
 ch_close_in({handle})		none	close in part of {handle}
 ch_evalexpr({handle}, {expr} [, {options}])
@@ -2980,16 +2981,28 @@ confirm({msg} [, {choices} [, {default} [, {type}]]])
 		don't fit, a vertical layout is used anyway.  For some systems
 		the horizontal layout is always used.
 
+ch_canread({handle})						*ch_canread()*
+		Return non-zero when there is something to read from {handle}.
+		{handle} can be a Channel or a Job that has a Channel.
+
+		This is useful to read from a channel at a convenient time,
+		e.g. from a timer.
+
+		Note that messages are dropped when the channel does not have
+		a callback.  Add a close callback to avoid that.
+
+		{only available when compiled with the |+channel| feature}
+
 ch_close({handle})						*ch_close()*
 		Close {handle}.  See |channel-close|.
-		{handle} can be Channel or a Job that has a Channel.
+		{handle} can be a Channel or a Job that has a Channel.
 		A close callback is not invoked.
 
 		{only available when compiled with the |+channel| feature}
 
 ch_close_in({handle})						*ch_close_in()*
 		Close the "in" part of {handle}.  See |channel-close-in|.
-		{handle} can be Channel or a Job that has a Channel.
+		{handle} can be a Channel or a Job that has a Channel.
 		A close callback is not invoked.
 
 		{only available when compiled with the |+channel| feature}
@@ -2998,7 +3011,7 @@ ch_evalexpr({handle}, {expr} [, {options}])			*ch_evalexpr()*
 		Send {expr} over {handle}.  The {expr} is encoded
 		according to the type of channel.  The function cannot be used
 		with a raw channel.  See |channel-use|.
-		{handle} can be Channel or a Job that has a Channel.
+		{handle} can be a Channel or a Job that has a Channel.
 								*E917*
 		{options} must be a Dictionary.  It must not have a "callback"
 		entry.  It can have a "timeout" entry to specify the timeout
@@ -3012,7 +3025,7 @@ ch_evalexpr({handle}, {expr} [, {options}])			*ch_evalexpr()*
 
 ch_evalraw({handle}, {string} [, {options}])		*ch_evalraw()*
 		Send {string} over {handle}.
-		{handle} can be Channel or a Job that has a Channel.
+		{handle} can be a Channel or a Job that has a Channel.
 
 		Works like |ch_evalexpr()|, but does not encode the request or
 		decode the response.  The caller is responsible for the
@@ -3025,7 +3038,7 @@ ch_evalraw({handle}, {string} [, {options}])		*ch_evalraw()*
 
 ch_getbufnr({handle}, {what})				 *ch_getbufnr()*
 		Get the buffer number that {handle} is using for {what}.
-		{handle} can be Channel or a Job that has a Channel.
+		{handle} can be a Channel or a Job that has a Channel.
 		{what} can be "err" for stderr, "out" for stdout or empty for
 		socket output.
 		Returns -1 when there is no buffer.
@@ -3099,7 +3112,7 @@ ch_open({address} [, {options}])				*ch_open()*
 
 ch_read({handle} [, {options}])					*ch_read()*
 		Read from {handle} and return the received message.
-		{handle} can be Channel or a Job that has a Channel.
+		{handle} can be a Channel or a Job that has a Channel.
 		See |channel-more|.
 		{only available when compiled with the |+channel| feature}
 
@@ -3113,7 +3126,7 @@ ch_sendexpr({handle}, {expr} [, {options}])			*ch_sendexpr()*
 		according to the type of channel.  The function cannot be used
 		with a raw channel.
 		See |channel-use|.				*E912*
-		{handle} can be Channel or a Job that has a Channel.
+		{handle} can be a Channel or a Job that has a Channel.
 
 		{only available when compiled with the |+channel| feature}
 
@@ -3134,7 +3147,7 @@ ch_setoptions({handle}, {options})			*ch_setoptions()*
 			"timeout"	default read timeout in msec
 			"mode"		mode for the whole channel
 		See |ch_open()| for more explanation.
-		{handle} can be Channel or a Job that has a Channel.
+		{handle} can be a Channel or a Job that has a Channel.
 
 		Note that changing the mode may cause queued messages to be
 		lost.
@@ -3148,7 +3161,7 @@ ch_status({handle} [, {options}])				*ch_status()*
 			"open"		channel can be used
 			"buffered"	channel can be read, not written to
 			"closed"	channel can not be used
-		{handle} can be Channel or a Job that has a Channel.
+		{handle} can be a Channel or a Job that has a Channel.
 		"buffered" is used when the channel was closed but there is
 		still data that can be obtained with |ch_read()|.
 
diff --git a/src/channel.c b/src/channel.c
index 6c5a4ff1d6..e5f28003ee 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -2603,7 +2603,7 @@ channel_is_open(channel_T *channel)
 /*
  * Return TRUE if "channel" has JSON or other typeahead.
  */
-    static int
+    int
 channel_has_readahead(channel_T *channel, ch_part_T part)
 {
     ch_mode_T	ch_mode = channel->ch_part[part].ch_mode;
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 846a914165..88e4852fea 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -76,6 +76,7 @@ static void f_call(typval_T *argvars, typval_T *rettv);
 static void f_ceil(typval_T *argvars, typval_T *rettv);
 #endif
 #ifdef FEAT_JOB_CHANNEL
+static void f_ch_canread(typval_T *argvars, typval_T *rettv);
 static void f_ch_close(typval_T *argvars, typval_T *rettv);
 static void f_ch_close_in(typval_T *argvars, typval_T *rettv);
 static void f_ch_evalexpr(typval_T *argvars, typval_T *rettv);
@@ -499,6 +500,7 @@ static struct fst
     {"ceil",		1, 1, f_ceil},
 #endif
 #ifdef FEAT_JOB_CHANNEL
+    {"ch_canread",	1, 1, f_ch_canread},
     {"ch_close",	1, 1, f_ch_close},
     {"ch_close_in",	1, 1, f_ch_close_in},
     {"ch_evalexpr",	2, 3, f_ch_evalexpr},
@@ -1779,6 +1781,21 @@ f_ceil(typval_T *argvars, typval_T *rettv)
 
 #ifdef FEAT_JOB_CHANNEL
 /*
+ * "ch_canread()" function
+ */
+    static void
+f_ch_canread(typval_T *argvars, typval_T *rettv)
+{
+    channel_T *channel = get_channel_arg(&argvars[0], TRUE, TRUE, 0);
+
+    rettv->vval.v_number = 0;
+    if (channel != NULL)
+	rettv->vval.v_number = channel_has_readahead(channel, PART_SOCK)
+			    || channel_has_readahead(channel, PART_OUT)
+			    || channel_has_readahead(channel, PART_ERR);
+}
+
+/*
  * "ch_close()" function
  */
     static void
diff --git a/src/proto/channel.pro b/src/proto/channel.pro
index 8640fa7bb7..f127268ed1 100644
--- a/src/proto/channel.pro
+++ b/src/proto/channel.pro
@@ -25,6 +25,7 @@ void channel_consume(channel_T *channel, ch_part_T part, int len);
 int channel_collapse(channel_T *channel, ch_part_T part, int want_nl);
 int channel_can_write_to(channel_T *channel);
 int channel_is_open(channel_T *channel);
+int channel_has_readahead(channel_T *channel, ch_part_T part);
 char *channel_status(channel_T *channel, int req_part);
 void channel_info(channel_T *channel, dict_T *dict);
 void channel_close(channel_T *channel, int invoke_close_cb);
diff --git a/src/testdir/shared.vim b/src/testdir/shared.vim
index 45a2ea496d..8160af3851 100644
--- a/src/testdir/shared.vim
+++ b/src/testdir/shared.vim
@@ -88,7 +88,7 @@ func RunServer(cmd, testfunc, args)
 
     call call(function(a:testfunc), [port])
   catch
-    call assert_false(1, "Caught exception: " . v:exception)
+    call assert_false(1, 'Caught exception: "' . v:exception . '" in ' . v:throwpoint)
   finally
     call s:kill_server(a:cmd)
   endtry
diff --git a/src/testdir/test_channel.vim b/src/testdir/test_channel.vim
index 42e0e04b81..85f80e25cc 100644
--- a/src/testdir/test_channel.vim
+++ b/src/testdir/test_channel.vim
@@ -58,6 +58,9 @@ func Ch_communicate(port)
   " string with ][ should work
   call assert_equal('this][that', ch_evalexpr(handle, 'echo this][that'))
 
+  " nothing to read now
+  call assert_equal(0, ch_canread(handle))
+
   " sending three messages quickly then reading should work
   for i in range(3)
     call ch_sendexpr(handle, 'echo hello ' . i)
@@ -368,7 +371,7 @@ func Ch_raw_one_time_callback(port)
   endif
   call ch_setoptions(handle, {'mode': 'raw'})
 
-  " The message are sent raw, we do our own JSON strings here.
+  " The messages are sent raw, we do our own JSON strings here.
   call ch_sendraw(handle, "[1, \"hello!\"]\n", {'callback': 'Ch_handleRaw1'})
   call WaitFor('g:Ch_reply1 != ""')
   call assert_equal("[1, \"got it\"]", g:Ch_reply1)
@@ -431,7 +434,10 @@ func Test_raw_pipe()
     return
   endif
   call ch_log('Test_raw_pipe()')
-  let job = job_start(s:python . " test_channel_pipe.py", {'mode': 'raw'})
+  " Add a dummy close callback to avoid that messages are dropped when calling
+  " ch_canread().
+  let job = job_start(s:python . " test_channel_pipe.py",
+	\ {'mode': 'raw', 'close_cb': {chan -> 0}})
   call assert_equal(v:t_job, type(job))
   call assert_equal("run", job_status(job))
 
@@ -458,6 +464,9 @@ func Test_raw_pipe()
     call assert_equal("something\n", substitute(msg, "\r", "", 'g'))
 
     call ch_sendraw(job, "double this\n")
+    let g:handle = job_getchannel(job)
+    call WaitFor('ch_canread(g:handle)')
+    unlet g:handle
     let msg = ch_readraw(job)
     call assert_equal("this\nAND this\n", substitute(msg, "\r", "", 'g'))
 
diff --git a/src/version.c b/src/version.c
index 0e3554ddcb..02d1be454b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@ static char *(features[]) =
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    105,
+/**/
     104,
 /**/
     103,