Enable system LanguageTool. Resolve #15.

README.rst

@@ -70,6 +70,9 @@ To overwrite the host part of URL that is used to download LanguageTool-{version
 
     - SET LANGUAGE_CHECK_DOWNLOAD_HOST = [alternate URL]
 
+To use an existing installation of LanguageTool in the CLASSPATH rather than downloading it::
+
+    - SET LANGUAGE_CHECK_SYSTEM_LANGUAGETOOL = 1
 
 Prerequisites
 -------------

language_check/__init__.py

@@ -568,9 +568,6 @@ def get_lt_dir(base_dir):
                 pass
             else:
                 language_check_dir = get_lt_dir(base_dir)
-            if not language_check_dir:
-                raise PathError("can't find LanguageTool directory in {!r}"
-                                .format(base_dir))
         cache['language_check_dir'] = language_check_dir
     return language_check_dir
 
@@ -594,8 +591,12 @@ def get_server_cmd(port=None):
         cmd = cache['server_cmd']
     except KeyError:
         java_path, jar_path = get_jar_info()
-        cmd = [java_path, '-cp', jar_path,
-               'org.languagetool.server.HTTPServer']
+
+        cmd = [java_path]
+        if jar_path:
+            cmd.extend(['-cp', jar_path])
+        cmd.append('org.languagetool.server.HTTPServer')
+
         cache['server_cmd'] = cmd
     return cmd if port is None else cmd + ['-p', str(port)]
 
@@ -609,17 +610,18 @@ def get_jar_info():
             raise JavaError("can't find Java")
         dir_name = get_directory()
         jar_path = None
-        for jar_name in JAR_NAMES:
-            for jar_path in glob.glob(os.path.join(dir_name, jar_name)):
-                if os.path.isfile(jar_path):
+        if dir_name:  # If no directory was found, assume jars are in CLASSPATH.
+            for jar_name in JAR_NAMES:
+                for jar_path in glob.glob(os.path.join(dir_name, jar_name)):
+                    if os.path.isfile(jar_path):
+                        break
+                else:
+                    jar_path = None
+                if jar_path:
                     break
             else:
-                jar_path = None
-            if jar_path:
-                break
-        else:
-            raise PathError("can't find languagetool-standalone in {!r}"
-                            .format(dir_name))
+                raise PathError("can't find languagetool-standalone in {!r}"
+                                .format(dir_name))
         cache['jar_info'] = java_path, jar_path
     return java_path, jar_path
 

setup.py

@@ -581,7 +581,8 @@ def language_tool_hook(config):
         del config['files']['package_data']
     elif any(arg.startswith(('install', 'build', 'bdist'))
              for arg in sys.argv):
-        download_lt()
+        if not os.environ.get('LANGUAGE_CHECK_SYSTEM_LANGUAGETOOL'):
+            download_lt()
 
 
 def main():