patch 8.2.4981: it is not possible to manipulate autocommands

Problem:    It is not possible to manipulate autocommands.
Solution:   Add functions to add, get and set autocommands. (Yegappan
            Lakshmanan, closes #10291)

Author: yegappan

runtime/doc/autocmd.txt

@@ -82,6 +82,9 @@ triggered.
 		  /<start
 		}
 
+The |autocmd_add()| function can be used to add a list of autocmds and autocmd
+groups from a Vim script.
+
 Note: The ":autocmd" command can only be followed by another command when the
 '|' appears where the pattern is expected.  This works: >
 	:augroup mine | au! BufRead | augroup END
@@ -146,6 +149,9 @@ prompt.  When one command outputs two messages this can happen anyway.
 ==============================================================================
 3. Removing autocommands				*autocmd-remove*
 
+In addition to the below described commands, the |autocmd_delete()| function can
+be used to remove a list of autocmds and autocmd groups from a Vim script.
+
 :au[tocmd]! [group] {event} {aupat} [++once] [++nested] {cmd}
 			Remove all autocommands associated with {event} and
 			{aupat}, and add the command {cmd}.
@@ -198,6 +204,9 @@ argument behavior differs from that for defining and removing autocommands.
 In order to list buffer-local autocommands, use a pattern in the form <buffer>
 or <buffer=N>.  See |autocmd-buflocal|.
 
+The |autocmd_get()| function can be used from a Vim script to get a list of
+autocmds.
+
 							*:autocmd-verbose*
 When 'verbose' is non-zero, listing an autocommand will also display where it
 was last defined. Example: >

runtime/doc/builtin.txt

@@ -60,6 +60,9 @@ assert_report({msg})		Number	report a test failure
 assert_true({actual} [, {msg}])	Number	assert {actual} is true
 atan({expr})			Float	arc tangent of {expr}
 atan2({expr1}, {expr2})		Float	arc tangent of {expr1} / {expr2}
+autocmd_add({acmds})		Bool	add a list of autocmds and groups
+autocmd_delete({acmds})		Bool	delete a list of autocmds and groups
+autocmd_get([{opts}])		List	return a list of autocmds
 balloon_gettext()		String	current text in the balloon
 balloon_show({expr})		none	show {expr} inside the balloon
 balloon_split({msg})		List	split {msg} as used for a balloon
@@ -922,6 +925,145 @@ atan2({expr1}, {expr2})					*atan2()*
 <
 		{only available when compiled with the |+float| feature}
 
+
+autocmd_add({acmds})					*autocmd_add()*
+		Adds a List of autocmds and autocmd groups.
+
+		The {acmds} argument is a List where each item is a Dict with
+		the following optional items:
+		    bufnr	buffer number to add a buffer-local autocmd.
+				If this item is specified, then the "pattern"
+				item is ignored.
+		    cmd		Ex command to execute for this autocmd event
+		    event	autocmd event name. Refer to |autocmd-events|.
+		    group	autocmd group name. Refer to |autocmd-groups|.
+				If this group doesn't exist then it is
+				created.  If not specified or empty, then the
+				default group is used.
+		    nested	set to v:true to add a nested autocmd.
+				Refer to |autocmd-nested|.
+		    once	set to v:true to add a autocmd which executes
+				only once. Refer to |autocmd-once|.
+		    pattern	autocmd pattern string. Refer to
+				|autocmd-patterns|.  If "bufnr" item is
+				present, then this item is ignored.
+
+		Returns v:true on success and v:false on failure.
+		Examples: >
+			" Create a buffer-local autocmd for buffer 5
+			let acmd = {}
+			let acmd.group = 'MyGroup'
+			let acmd.event = 'BufEnter'
+			let acmd.bufnr = 5
+			let acmd.cmd = 'call BufEnterFunc()'
+			call autocmd_add([acmd])
+
+		Can also be used as a |method|: >
+			GetAutocmdList()->autocmd_add()
+<
+autocmd_delete({acmds})					*autocmd_delete()*
+		Deletes a List of autocmds and autocmd groups.
+
+		The {acmds} argument is a List where each item is a Dict with
+		the following optional items:
+		    bufnr	buffer number to delete a buffer-local autocmd.
+				If this item is specified, then the "pattern"
+				item is ignored.
+		    cmd		Ex command for this autocmd event
+		    event	autocmd event name. Refer to |autocmd-events|.
+				If '*' then all the autocmd events in this
+				group are deleted.
+		    group	autocmd group name. Refer to |autocmd-groups|.
+				If not specified or empty, then the default
+				group is used.
+		    nested	set to v:true for a nested autocmd.
+				Refer to |autocmd-nested|.
+		    once	set to v:true for an autocmd which executes
+				only once. Refer to |autocmd-once|.
+		    pattern	autocmd pattern string. Refer to
+				|autocmd-patterns|.  If "bufnr" item is
+				present, then this item is ignored.
+
+		If only {group} is specified in a {acmds} entry and {event},
+		{pattern} and {cmd} are not specified, then that autocmd group
+		is deleted.
+
+		Returns v:true on success and v:false on failure.
+		Examples: >
+			" :autocmd! BufLeave *.vim
+			let acmd = #{event: 'BufLeave', pattern: '*.vim'}
+			call autocmd_delete([acmd]})
+			" :autocmd! MyGroup1 BufLeave
+			let acmd = #{group: 'MyGroup1', event: 'BufLeave'}
+			call autocmd_delete([acmd])
+			" :autocmd! MyGroup2 BufEnter *.c
+			let acmd = #{group: 'MyGroup2', event: 'BufEnter',
+							\ pattern: '*.c'}
+			" :autocmd! MyGroup2 * *.c
+			let acmd = #{group: 'MyGroup2', event: '*',
+							\ pattern: '*.c'}
+			call autocmd_delete([acmd])
+			" :autocmd! MyGroup3
+			let acmd = #{group: 'MyGroup3'}
+			call autocmd_delete([acmd])
+<
+		Can also be used as a |method|: >
+			GetAutocmdList()->autocmd_delete()
+
+autocmd_get([{opts}])					*autocmd_get()*
+		Returns a |List| of autocmds. If {opts} is not supplied, then
+		returns the autocmds for all the events in all the groups.
+
+		The optional {opts} Dict argument supports the following
+		items:
+		    group	Autocmd group name. If specified, returns only
+				the autocmds defined in this group. If the
+				specified group doesn't exist, results in an
+				error message.  If set to an empty string,
+				then the default autocmd group is used.
+		    event	Autocmd event name. If specified, returns only
+				the autocmds defined for this event.  If set
+				to "*", then returns autocmds for all the
+				events.  If the specified event doesn't exist,
+				results in an error message.
+		    pattern	Autocmd pattern. If specified, returns only
+				the autocmds defined for this pattern.
+		A combination of the above three times can be supplied in
+		{opts}.
+
+		Each Dict in the returned List contains the following items:
+		    bufnr	For buffer-local autocmds, buffer number where
+				the autocmd is defined.
+		    cmd		Command executed for this autocmd.
+		    event	Autocmd event name.
+		    group	Autocmd group name.
+		    nested	Set to v:true for a nested autocmd. See
+				|autocmd-nested|.
+		    once	Set to v:true, if the autocmd will be executed
+				only once. See |autocmd-once|.
+		    pattern	Autocmd pattern.  For a buffer-local
+				autocmd, this will be of the form "<buffer=n>".
+		If there are multiple commands for an autocmd event in a
+		group, then separate items are returned for each command.
+
+		Examples: >
+			" :autocmd MyGroup
+			echo autocmd_get(#{group: 'Mygroup'})
+			" :autocmd G BufUnload
+			echo autocmd_get(#{group: 'G', event: 'BufUnload'})
+			" :autocmd G * *.ts
+			let acmd = #{group: 'G', event: '*', pattern: '*.ts'}
+			echo autocmd_get(acmd)
+			" :autocmd Syntax
+			echo autocmd_get(#{event: 'Syntax'})
+			" :autocmd G BufEnter *.ts
+			let acmd = #{group: 'G', event: 'BufEnter',
+							\ pattern: '*.ts'}
+			echo autocmd_get(acmd)
+<
+		Can also be used as a |method|: >
+			Getopts()->autocmd_get()
+<
 balloon_gettext()					*balloon_gettext()*
 		Return the current text in the balloon.  Only for the string,
 		not used for the List.

runtime/doc/usr_41.txt

@@ -925,6 +925,11 @@ Date and Time:				*date-functions* *time-functions*
 	reltimestr()		convert reltime() result to a string
 	reltimefloat()		convert reltime() result to a Float
 
+Autocmds:					*autocmd-functions*
+	autocmd_add()		add a list of autocmds and groups
+	autocmd_delete()	delete a list of autocmds and groups
+	autocmd_get()		return a list of autocmds
+
 			*buffer-functions* *window-functions* *arg-functions*
 Buffers, windows and the argument list:
 	argc()			number of entries in the argument list