[RFC] Restore node

DOC.md

@@ -28,6 +28,7 @@ local i = ls.insert_node
 local f = ls.function_node
 local c = ls.choice_node
 local d = ls.dynamic_node
+local r = ls.restore_node
 local events = require("luasnip.util.events")
 ```
 
@@ -393,6 +394,82 @@ eg. 3, it would change to "3\nSample Text\nSample Text\nSample Text". Text
 that was inserted into any of the dynamicNodes insertNodes is kept when
 changing to a bigger number.
 
+# RESTORENODE
+
+This node can store and restore a snippetNode that was modified (changed
+choices, inserted text) by the user. It's usage is best demonstrated by an
+example:
+
+```lua
+s("paren_change", {
+	c(1, {
+		sn(nil, { t("("), r(1, "user_text"), t(")") }),
+		sn(nil, { t("["), r(1, "user_text"), t("]") }),
+		sn(nil, { t("{"), r(1, "user_text"), t("}") }),
+	}),
+}, {
+	stored = {
+		user_text = i(1, "default_text")
+	}
+})
+```
+
+Here the text entered into `user_text` is preserved upon changing choice.
+
+The constructor for the restoreNode, `r`, takes (at most) three parameters:
+- `pos`, when to jump to this node.
+- `key`, the key that identifies which `restoreNode`s should share their
+  content.
+- `nodes`, the contents of the `restoreNode`. Can either be a single node or
+  a table of nodes (both of which will be wrapped inside a `snippetNode`,
+  except if the single node already is a `snippetNode`).
+  The content of a given key may be defined multiple times, but if the
+  contents differ, it's undefined which will actually be used.
+  If a keys content is defined in a `dynamicNode`, it will not be used for
+  `restoreNodes` outside that `dynamicNode`. A way around this limitation is
+  defining the content in the `restoreNode` outside the `dynamicNode`.
+
+The content for a key may also be defined in the `opts`-parameter of the
+snippet-constructor, as seen in the example above. The `stored`-table accepts
+the same values as the `nodes`-parameter passed to `r`.
+If no content is defined for a key, it defaults to the empty `insertNode`.
+
+The `restoreNode` is also useful for storing user-input across updates of a
+`dynamicNode`. Consider this:
+
+```lua
+local function simple_restore(args, _)
+	return sn(nil, {i(1, args[1]), i(2, "user_text")})
+end
+
+s("rest", {
+	i(1, "preset"), t{"",""},
+	d(2, simple_restore, 1)
+}),
+```
+
+Every time the `i(1)` in the outer snippet is changed, the text inside the
+`dynamicNode` is reset to `"user_text"`. This can be prevented by using a
+`restoreNode`:
+
+```lua
+local function simple_restore(args, _)
+	return sn(nil, {i(1, args[1]), r(2, "dyn", i(nil, "user_text"))})
+end
+
+ss("rest", {
+	i(1, "preset"), t{"",""},
+	d(2, simple_restore, 1)
+}),
+("rest", {
+	i(1, "preset"), t{"",""},
+	d(2, simple_restore, 1)
+}),
+```
+Now the entered text is stored.
+
+`RestoreNode`s indent is not influenced by `indentSnippetNodes` right now. If
+that really bothers you feel free to open an issue.
 
 # EXTRAS
 

Examples/snippets.lua

@@ -7,8 +7,9 @@ local i = ls.insert_node
 local f = ls.function_node
 local c = ls.choice_node
 local d = ls.dynamic_node
+local r = ls.restore_node
 local l = require("luasnip.extras").lambda
-local r = require("luasnip.extras").rep
+local rep = require("luasnip.extras").rep
 local p = require("luasnip.extras").partial
 local m = require("luasnip.extras").match
 local n = require("luasnip.extras").nonempty
@@ -58,6 +59,9 @@ end
 
 -- complicated function for dynamicNode.
 local function jdocsnip(args, _, old_state)
+	-- !!! old_state is used to preserve user-input here. DON'T DO IT THAT WAY!
+	-- Using a restoreNode instead is much easier.
+	-- View this only as an example on how old_state functions.
 	local nodes = {
 		t({ "/**", " * " }),
 		i(1, "A short Description"),
@@ -200,12 +204,15 @@ ls.snippets = {
 				-- Inside Choices, Nodes don't need a position as the choice node is the one being jumped to.
 				sn(nil, {
 					t("extends "),
-					i(1),
+					-- restoreNode: stores and restores nodes.
+					-- pass position, store-key and nodes.
+					r(1, "other_class", i(1)),
 					t(" {"),
 				}),
 				sn(nil, {
 					t("implements "),
-					i(1),
+					-- no need to define the nodes for a given key a second time.
+					r(1, "other_class"),
 					t(" {"),
 				}),
 			}),
@@ -309,7 +316,7 @@ ls.snippets = {
 			i(0),
 		}),
 		-- Shorthand for repeating the text in a given node.
-		s("repeat", { i(1, "text"), t({ "", "" }), r(1) }),
+		s("repeat", { i(1, "text"), t({ "", "" }), rep(1) }),
 		-- Directly insert the ouput from a function evaluated at runtime.
 		s("part", p(os.date, "%Y")),
 		-- use matchNodes to insert text based on a pattern/function/lambda-evaluation.
@@ -391,9 +398,9 @@ ls.snippets = {
 			]],
 				{
 					i(1, "x"),
-					r(1),
+					rep(1),
 					i(2, "y"),
-					r(2),
+					rep(2),
 				}
 			)
 		),

doc/luasnip.txt

@@ -12,16 +12,17 @@ CONTENTS                                                        *luasnip-content
 6. SNIPPETNODE...............................................|luasnip-snippetnode|
 7. INDENTSNIPPETNODE...................................|luasnip-indentsnippetnode|
 8. DYNAMICNODE...............................................|luasnip-dynamicnode|
-9. EXTRAS.........................................................|luasnip-extras|
-10. LSP-SNIPPETS............................................|luasnip-lsp-snippets|
-11. VARIABLES..................................................|luasnip-variables|
-12. VSCODE SNIPPETS LOADER........................|luasnip-vscode_snippets_loader|
-13. EXT_OPTS....................................................|luasnip-ext_opts|
-14. DOCSTRING..................................................|luasnip-docstring|
-15. DOCSTRING-CACHE......................................|luasnip-docstring-cache|
-16. EVENTS........................................................|luasnip-events|
-17. CLEANUP......................................................|luasnip-cleanup|
-18. API-REFERENCE..........................................|luasnip-api-reference|
+9. RESTORENODE...............................................|luasnip-restorenode|
+10. EXTRAS........................................................|luasnip-extras|
+11. LSP-SNIPPETS............................................|luasnip-lsp-snippets|
+12. VARIABLES..................................................|luasnip-variables|
+13. VSCODE SNIPPETS LOADER........................|luasnip-vscode_snippets_loader|
+14. EXT_OPTS....................................................|luasnip-ext_opts|
+15. DOCSTRING..................................................|luasnip-docstring|
+16. DOCSTRING-CACHE......................................|luasnip-docstring-cache|
+17. EVENTS........................................................|luasnip-events|
+18. CLEANUP......................................................|luasnip-cleanup|
+19. API-REFERENCE..........................................|luasnip-api-reference|
 >
                 __                       ____                          
                /\ \                     /\  _`\           __           
@@ -51,6 +52,7 @@ All code-snippets in this help assume that
     local f = ls.function_node
     local c = ls.choice_node
     local d = ls.dynamic_node
+    local r = ls.restore_node
     local events = require("luasnip.util.events")
 <
 
@@ -408,6 +410,80 @@ eg. 3, it would change to "3\nSample Text\nSample Text\nSample Text". Text
 that was inserted into any of the dynamicNodes insertNodes is kept when
 changing to a bigger number.
 
+================================================================================
+RESTORENODE                                                  *luasnip-restorenode*
+
+This node can store and restore a snippetNode that was modified (changed
+choices, inserted text) by the user. It's usage is best demonstrated by an
+example:
+>
+    s("paren_change", {
+    	c(1, {
+    		sn(nil, { t("("), r(1, "user_text"), t(")") }),
+    		sn(nil, { t("["), r(1, "user_text"), t("]") }),
+    		sn(nil, { t("{"), r(1, "user_text"), t("}") }),
+    	}),
+    }, {
+    	stored = {
+    		user_text = i(1, "default_text")
+    	}
+    })
+<
+
+Here the text entered into `user_text` is preserved upon changing choice.
+
+The constructor for the restoreNode, `r`, takes (at most) three parameters:
+- `pos`, when to jump to this node.
+- `key`, the key that identifies which `restoreNode`s should share their
+  content.
+- `nodes`, the contents of the `restoreNode`. Can either be a single node or
+  a table of nodes (both of which will be wrapped inside a `snippetNode`,
+  except if the single node already is a `snippetNode`).
+  The content of a given key may be defined multiple times, but if the
+  contents differ, it's undefined which will actually be used.
+  If a keys content is defined in a `dynamicNode`, it will not be used for
+  `restoreNodes` outside that `dynamicNode`. A way around this limitation is
+  defining the content in the `restoreNode` outside the `dynamicNode`.
+
+The content for a key may also be defined in the `opts`-parameter of the
+snippet-constructor, as seen in the example above. The `stored`-table accepts
+the same values as the `nodes`-parameter passed to `r`.
+If no content is defined for a key, it defaults to the empty `insertNode`.
+
+The `restoreNode` is also useful for storing user-input across updates of a
+`dynamicNode`. Consider this:
+>
+    local function simple_restore(args, _)
+    	return sn(nil, {i(1, args[1]), i(2, "user_text")})
+    end
+    s("rest", {
+    	i(1, "preset"), t{"",""},
+    	d(2, simple_restore, 1)
+    }),
+<
+
+Every time the `i(1)` in the outer snippet is changed, the text inside the
+`dynamicNode` is reset to `"user_text"`. This can be prevented by using a
+`restoreNode`:
+>
+    local function simple_restore(args, _)
+    	return sn(nil, {i(1, args[1]), r(2, "dyn", i(nil, "user_text"))})
+    end
+    ss("rest", {
+    	i(1, "preset"), t{"",""},
+    	d(2, simple_restore, 1)
+    }),
+    ("rest", {
+    	i(1, "preset"), t{"",""},
+    	d(2, simple_restore, 1)
+    }),
+<
+
+Now the entered text is stored.
+
+`RestoreNode`s indent is not influenced by `indentSnippetNodes` right now. If
+that really bothers you feel free to open an issue.
+
 ================================================================================
 EXTRAS                                                            *luasnip-extras*
 

lua/luasnip/config.lua

@@ -60,6 +60,13 @@ local defaults = {
 			-- not used!
 			snippet_passive = { hl_group = "LuasnipSnippetSnippetPassive" },
 		},
+		[types.restoreNode] = {
+			active = { hl_group = "LuasnipRestoreNodeActive" },
+			passive = { hl_group = "LuasnipRestoreNodePassive" },
+			snippet_passive = {
+				hl_group = "LuasnipRestoreNodeSnippetPassive",
+			},
+		},
 	},
 	ext_base_prio = 200,
 	ext_prio_increase = 7,

lua/luasnip/init.lua

@@ -438,6 +438,7 @@ ls = {
 	i = require("luasnip.nodes.insertNode").I,
 	c = require("luasnip.nodes.choiceNode").C,
 	d = require("luasnip.nodes.dynamicNode").D,
+	r = require("luasnip.nodes.restoreNode").R,
 	snippet = snip_mod.S,
 	snippet_node = snip_mod.SN,
 	parent_indexer = snip_mod.P,
@@ -447,6 +448,7 @@ ls = {
 	insert_node = require("luasnip.nodes.insertNode").I,
 	choice_node = require("luasnip.nodes.choiceNode").C,
 	dynamic_node = require("luasnip.nodes.dynamicNode").D,
+	restore_node = require("luasnip.nodes.restoreNode").R,
 	parser = require("luasnip.util.parser"),
 	config = require("luasnip.config"),
 	snippets = { all = {} },

lua/luasnip/nodes/choiceNode.lua

@@ -169,14 +169,20 @@ function ChoiceNode:change_choice(dir)
 	self.active_choice:store()
 	-- tear down current choice.
 	self.active_choice:input_leave()
+	self.active_choice:exit()
+
+	-- store in old_choice, active_choice has to be disabled to prevent reading
+	-- from cleared mark in set_mark_rgrav (which will be called in
+	-- parent:set_text(self,...) a few lines below).
+	local old_choice = self.active_choice
+	self.active_choice = nil
+
 	-- clear text.
 	self.parent:set_text(self, { "" })
 
-	self.active_choice:exit()
-
 	-- stylua: ignore
-	self.active_choice = dir == 1 and self.active_choice.next_choice
-	                               or self.active_choice.prev_choice
+	self.active_choice = dir == 1 and old_choice.next_choice
+	                               or old_choice.prev_choice
 
 	self.active_choice.mark = self.mark:copy_pos_gravs(
 		vim.deepcopy(self.parent.ext_opts[self.active_choice.type].passive)
@@ -218,7 +224,10 @@ end
 -- val_begin/end may be nil, in this case that gravity won't be changed.
 function ChoiceNode:set_mark_rgrav(rgrav_beg, rgrav_end)
 	node.set_mark_rgrav(self, rgrav_beg, rgrav_end)
-	self.active_choice:set_mark_rgrav(rgrav_beg, rgrav_end)
+	-- may be set to temporarily in change_choice.
+	if self.active_choice then
+		self.active_choice:set_mark_rgrav(rgrav_beg, rgrav_end)
+	end
 end
 
 function ChoiceNode:set_ext_opts(name)

lua/luasnip/nodes/dynamicNode.lua

@@ -120,15 +120,16 @@ function DynamicNode:update()
 			self.snip.old_state,
 			unpack(self.user_args)
 		)
+		self.snip:exit()
+		self.snip = nil
+
 		-- enters node.
 		self.parent:set_text(self, { "" })
-		self.snip:exit()
 	else
 		-- also enter node here.
 		self.parent:enter_node(self.indx)
 		tmp = self.fn(self.last_args, self.parent, nil, unpack(self.user_args))
 	end
-	self.snip = nil
 
 	-- act as if snip is directly inside parent.
 	tmp.parent = self.parent
@@ -193,12 +194,18 @@ end
 function DynamicNode:update_restore()
 	-- only restore snippet if arg-values still match.
 	if self.snip and vim.deep_equal(self:get_args(), self.last_args) then
-		self.snip.mark = self.mark:copy_pos_gravs(
+		-- prevent entering the uninitialized snip in enter_node in a few lines.
+		local tmp = self.snip
+		self.snip = nil
+
+		tmp.mark = self.mark:copy_pos_gravs(
 			vim.deepcopy(self.parent.ext_opts[types.snippetNode].passive)
 		)
 		self.parent:enter_node(self.indx)
-		self.snip:put_initial(self.mark:pos_begin_raw())
-		self.snip:update_restore()
+		tmp:put_initial(self.mark:pos_begin_raw())
+		tmp:update_restore()
+
+		self.snip = tmp
 	else
 		self:update()
 	end