fix(treesitter): TSNode:field() returns all children with the given field

runtime/doc/treesitter.txt

@@ -713,7 +713,7 @@ TSNode:extra()                                                *TSNode:extra()*
         (`boolean`)
 
 TSNode:field({name})                                          *TSNode:field()*
-    Returns a table of the nodes corresponding to the {name} field.
+    Returns a list of all the node's children that have the given field name.
 
     Parameters: ~
       • {name}  (`string`)

runtime/lua/vim/treesitter/_meta/tsnode.lua

@@ -43,7 +43,7 @@ function TSNode:prev_named_sibling() end
 --- @return fun(): TSNode, string
 function TSNode:iter_children() end
 
---- Returns a table of the nodes corresponding to the {name} field.
+--- Returns a list of all the node's children that have the given field name.
 --- @param name string
 --- @return TSNode[]
 function TSNode:field(name) end

src/nvim/lua/treesitter.c

@@ -998,16 +998,21 @@ static int node_symbol(lua_State *L)
 static int node_field(lua_State *L)
 {
   TSNode node = node_check(L, 1);
+  uint32_t count = ts_node_child_count(node);
+  int curr_index = 0;
 
   size_t name_len;
   const char *field_name = luaL_checklstring(L, 2, &name_len);
 
-  lua_newtable(L);  // [table]
+  lua_newtable(L);
 
-  TSNode field = ts_node_child_by_field_name(node, field_name, (uint32_t)name_len);
-  if (!ts_node_is_null(field)) {
-    push_node(L, field, 1);  // [table, node]
-    lua_rawseti(L, -2, 1);
+  for (uint32_t i = 0; i < count; i++) {
+    const char *child_field_name = ts_node_field_name_for_child(node, i);
+    if (strequal(field_name, child_field_name)) {
+      TSNode child = ts_node_child(node, i);
+      push_node(L, child, 1);
+      lua_rawseti(L, -2, ++curr_index);
+    }
   }
 
   return 1;

test/functional/treesitter/node_spec.lua

@@ -186,4 +186,23 @@ describe('treesitter node API', function()
     eq(lua_eval('value:type()'), lua_eval('declarator:child_with_descendant(value):type()'))
     eq(vim.NIL, lua_eval('value:child_with_descendant(value)'))
   end)
+
+  it('gets all children with a given field name', function()
+    insert([[
+      function foo(a,b,c)
+      end
+    ]])
+
+    exec_lua(function()
+      local tree = vim.treesitter.get_parser(0, 'lua'):parse()[1]
+      _G.parameters_node = assert(tree:root():named_descendant_for_range(0, 18, 0, 18))
+      _G.children_by_field = _G.parameters_node:field('name')
+    end)
+
+    eq('parameters', lua_eval('parameters_node:type()'))
+    eq(3, lua_eval('#children_by_field'))
+    eq('a', lua_eval('vim.treesitter.get_node_text(children_by_field[1], 0)'))
+    eq('b', lua_eval('vim.treesitter.get_node_text(children_by_field[2], 0)'))
+    eq('c', lua_eval('vim.treesitter.get_node_text(children_by_field[3], 0)'))
+  end)
 end)