Drop passing has_differences around, fixing an issue with generating files called '-'

Signed-off-by: Chris Lamb <lamby@debian.org>

diffoscope/presenters/formats.py

@@ -76,7 +76,7 @@ class PresenterManager(object):
 
         # If no output specified, default to printing --text output to stdout
         if not self.config:
-            parsed_args.text_output = FORMATS['text']['target'] = '-'
+            FORMATS['text']['target'] = '-'
             self.config['text'] = FORMATS['text']
 
         logger.debug(
@@ -85,16 +85,25 @@ class PresenterManager(object):
         )
 
     def output(self, difference, parsed_args, has_differences):
+        # As a special case, write an empty file instead of an empty diff.
+        if not has_differences:
+            try:
+                target = self.config['text']['target']
+
+                if target != '-':
+                    open(target, 'w').close()
+            except KeyError:
+                pass
+            return
+
+        if difference is None:
+            return
+
         for name, data in self.config.items():
             logger.debug("Generating %r output at %r", name, data['target'])
 
             with profile('output', name):
-                data['klass'].run(
-                    data,
-                    difference,
-                    parsed_args,
-                    has_differences,
-                )
+                data['klass'].run(data, difference, parsed_args)
 
     def compute_visual_diffs(self):
         """

diffoscope/presenters/html/html.py

@@ -82,7 +82,7 @@ class HTMLPresenter(Presenter):
     supports_visual_diffs = True
 
     @classmethod
-    def run(cls, data, difference, parsed_args, has_differences):
+    def run(cls, data, difference, parsed_args):
         with make_printer(parsed_args.html_output) as fn:
             output_html(
                 difference,
@@ -93,7 +93,7 @@ class HTMLPresenter(Presenter):
 
 class HTMLDirectoryPresenter(HTMLPresenter):
     @classmethod
-    def run(cls, data, difference, parsed_args, has_differences):
+    def run(cls, data, difference, parsed_args):
         output_html_directory(
             parsed_args.html_output_directory,
             difference,

diffoscope/presenters/text.py

@@ -44,13 +44,8 @@ class TextPresenter(Presenter):
         super().__init__()
 
     @classmethod
-    def run(cls, data, difference, parsed_args, has_differences):
-        # As a special case, write an empty file instead of an empty diff.
-        if not has_differences:
-            open(parsed_args.text_output, 'w').close()
-            return
-
-        with make_printer(parsed_args.text_output or '-') as fn:
+    def run(cls, data, difference, parsed_args):
+        with make_printer(data['target']) as fn:
             color = {
                 'auto': fn.output.isatty(),
                 'never': False,

diffoscope/presenters/utils.py

@@ -29,7 +29,7 @@ class Presenter(object):
         self.depth = 0
 
     @classmethod
-    def run(cls, data, difference, parsed_args, has_differences):
+    def run(cls, data, difference, parsed_args):
         with make_printer(data['target']) as fn:
             cls(fn).start(difference)