Merge syntax config per block

syntax in g:vim_vue_plugin_config replaced the whole default, so
{'syntax': {'script': ['javascript', 'typescript']}} removed template
and style, which then had no highlight or indent. Replace the default
of each key separately, like vim-svelte-plugin. A block can be removed
by setting it to [].

README.md

@@ -92,6 +92,7 @@ It has the following options
         - `lang="..."` on block tag decides the effective syntax
         - When no valid `lang="..."` is present, the first syntax in the list will be used.
         - By default, only syntax files from `['$VIMRUNTIME', '$VIM/vimfiles', '$HOME/.vim']` are loaded. If none is found, then **full** syntax files, including those from plugins, will be loaded
+    - Each key replaces the default of the same key, so `{'syntax': {'script': ['javascript', 'typescript']}}` keeps `template` as `['html']` and `style` as `['css']`. Set a key to `[]` to remove the block
 - **full_syntax**: *string list*. Syntax whose **full** syntax files will always be loaded
 - **initial_indent**: *string list*. Tag/syntax with initial one tab indent. The format can be `tag.syntax`, `tag`, or `syntax`
 

autoload/vue.vim

@@ -28,10 +28,16 @@ function! s:MergeUserConfigIntoDefault(user)
         \'debug': 0,
         \}
 
+  " Each key of syntax replaces the default of the same key, so blocks not in
+  " user config keep their default syntax
   let user = a:user
   for key in keys(default)
     if has_key(user, key)
-      let default[key] = user[key]
+      if key ==# 'syntax' && type(user[key]) == v:t_dict
+        call extend(default[key], user[key])
+      else
+        let default[key] = user[key]
+      endif
     endif
   endfor
 

test/cases/no-css.vim

@@ -1,5 +1,8 @@
-" Without css syntax, like only script in config
-let g:vim_vue_plugin_config = {'syntax': {'script': ['javascript']}}
+" Without css syntax, like only script in config, removing template and style
+" by []
+let g:vim_vue_plugin_config = {
+      \'syntax': {'script': ['javascript'], 'template': [], 'style': []},
+      \}
 let g:test_flatten = 1
 
 function! Check()

test/cases/syntax-merge.vim

@@ -0,0 +1,10 @@
+" Each key of syntax replaces the default of the same key, so template and
+" style keep html and css
+let g:vim_vue_plugin_config = {'syntax': {'script': ['javascript', 'typescript']}}
+let g:test_flatten = 1
+
+function! Check()
+  call ExpectBlock('<div>', 'template', 'html', 'htmlTemplateBlock')
+  call ExpectBlock('let count', 'script', 'typescript', 'typescriptScriptBlock')
+  call ExpectBlock('color: red', 'style', 'css', 'cssStyleBlock')
+endfunction

test/cases/syntax-merge.vue

@@ -0,0 +1,13 @@
+<template>
+  <div>{{ count }}</div>
+</template>
+
+<script lang="ts">
+let count: number = 0
+</script>
+
+<style>
+p {
+  color: red;
+}
+</style>