Improve auto completions (#350)

* Improve auto completions

1. Load .tags file relative to active view, the same way as for GotoSymbol
2. Directly iterate through .tags file without using awk.
3. Restrict auto completions to .tag files with 100MB of size or less.
4. Drop a lot of type conversions between lists and sets.
5. Don't return completions for metadata `!_TAG_...` lines.
6. Cache completions per tag_file. Doing so globally may have unwanted side
   effects when multiple projects/windows are open.
7. Drop extracting and merging with ST completions, as merging all sources is
   already performed by ST. No need to do it here.

* Fix typo

ctagsplugin.py

@@ -908,66 +908,51 @@ def tags_built(tag_file):
 
             tags_built(result)
 
-        GetAllCTagsList.ctags_list = []  # clear the cached ctags list
+        if tag_file in ctags_completions:
+            del ctags_completions[tag_file]  # clear the cached ctags list
 
 # Autocomplete commands
 
 
-class GetAllCTagsList():
-    """
-    Cache all the ctags list.
-    """
-    ctags_list = []
-
-    def __init__(self, list):
-        self.ctags_list = list
+ctags_completions = {}
 
 
 class CTagsAutoComplete(sublime_plugin.EventListener):
 
     def on_query_completions(self, view, prefix, locations):
-        if setting('autocomplete'):
-            prefix = prefix.strip().lower()
-            tags_path = view.window().folders()[0] + '/' + setting('tag_file')
+        if not setting('autocomplete'):
+            return None
 
-            sub_results = [v.extract_completions(prefix)
-                           for v in sublime.active_window().views()]
-            sub_results = [(item, item) for sublist in sub_results
-                           for item in sublist]  # flatten
+        prefix = prefix.lower()
 
-            if GetAllCTagsList.ctags_list:
-                results = [sublist for sublist in GetAllCTagsList.ctags_list
-                           if sublist[0].lower().startswith(prefix)]
-                results = sorted(set(results).union(set(sub_results)))
+        tags_path = find_tags_relative_to(
+            view.file_name(), setting('tag_file'))
 
-                return results
-            else:
-                tags = []
+        if not tags_path:
+            return None
 
-                # check if a project is open and the tags file exists
-                if not (view.window().folders() and os.path.exists(tags_path)):
-                    return tags
+        if not os.path.exists(tags_path):
+            return None
 
-                if sublime.platform() == "windows":
-                    prefix = ""
-                else:
-                    prefix = "\\"
+        if os.path.getsize(tags_path) > 100 * 1024 * 1024:
+            return None
+
+        if tags_path not in ctags_completions:
+            tags = set()
 
-                f = os.popen(
-                    "awk \"{ print " + prefix + "$1 }\" \"" + tags_path + "\"")
+            with open(tags_path, "r", encoding="utf-8") as fobj:
+                for line in fobj:
+                    line = line.strip()
+                    if not line or line.startswith("!_TAG"):
+                        continue
+                    cols = line.split("\t", 1)
+                    tags.add(cols[0])
 
-                for i in f.readlines():
-                    tags.append([i.strip()])
+            ctags_completions[tags_path] = tags
 
-                tags = [(item, item) for sublist in tags
-                        for item in sublist]  # flatten
-                tags = sorted(set(tags))  # make unique
-                GetAllCTagsList.ctags_list = tags
-                results = [sublist for sublist in GetAllCTagsList.ctags_list
-                           if sublist[0].lower().startswith(prefix)]
-                results = sorted(set(results).union(set(sub_results)))
+        return [tag for tag in ctags_completions[tags_path]
+                if tag.lower().startswith(prefix)]
 
-                return results
 
 # Test CTags commands