refactoring contexts, moved json writer to a class as it make more sense.

bonobo/io/json.py

@@ -1,18 +1,25 @@
 import json
 
-from bonobo.util.lifecycle import with_context, set_initializer, set_finalizer
+from bonobo.util.lifecycle import with_context
 
-__all__ = ['to_json', ]
+__all__ = [
+    'from_json',
+    'to_json',
+]
 
 
-def to_json(path_or_buf):
-    # todo different cases + documentation
-    # case 1: path_or_buf is str, we consider it filename, open and write
-    # case 2: pob is None, json should be yielded
-    # case 3: pob is stream, filelike, write, gogog.
+@with_context
+class JsonWriter:
+    def __init__(self, path_or_buf):
+        self.path_or_buf = path_or_buf
 
-    @with_context
-    def _to_json(ctx, row):
+    def initialize(self, ctx):
+        assert not hasattr(ctx, 'fp'), 'One at a time, baby.'
+        ctx.fp = open(self.path_or_buf, 'w+')
+        ctx.fp.write('[\n')
+        ctx.first = True
+
+    def __call__(self, ctx, row):
         if ctx.first:
             prefix = ''
             ctx.first = False
@@ -20,19 +27,14 @@ def to_json(path_or_buf):
             prefix = ',\n'
         ctx.fp.write(prefix + json.dumps(row))
 
-    @set_initializer(_to_json)
-    def _to_json_initialize(ctx):
-        assert not hasattr(ctx, 'fp'), 'One at a time, baby.'
-        ctx.fp = open(path_or_buf, 'w+')
-        ctx.fp.write('[\n')
-        ctx.first = True
-
-    @set_finalizer(_to_json)
-    def _to_json_finalize(ctx):
+    def finalize(self, ctx):
         ctx.fp.write('\n]')
         ctx.fp.close()
         del ctx.fp, ctx.first
 
-    _to_json.__name__ = 'to_json'
 
-    return _to_json
+def from_json(path_or_buf):
+    pass
+
+
+to_json = JsonWriter