Update progress after iteration (fix #651)

Reported "off by one" error is due to the fact that an interator is used
instead of a generator. As such there is no way for the bar to know when
it has iterated over the user's code block.

This commit swaps the iterator for a generator, and changes _when_ the
status report is updated, from before each iteration of a user's code
block, to _after_.

Updating the status report after the user's code has run allows the
report to convey how much work has been _done_ so far.

Accidental gain:
The associated unit test performs a black-box test on the generated
progress output. This test revealed a bug in the ETA time calculation
were the behavior differed between python 2 and 3, causing the unit test
to fail on python 3. The remedy employed to allow passing of the test is
to use integer division for the ETA calculation, which should also
address a related issue (fixes #485).

click/_termui_impl.py

@@ -102,7 +102,7 @@ def __iter__(self):
         if not self.entered:
             raise RuntimeError('You need to use progress bars in a with block.')
         self.render_progress()
-        return self
+        return self.generator()
 
     def render_finish(self):
         if self.is_hidden:
@@ -130,13 +130,13 @@ def eta(self):
 
     def format_eta(self):
         if self.eta_known:
-            t = self.eta + 1
+            t = int(self.eta)
             seconds = t % 60
-            t /= 60
+            t //= 60
             minutes = t % 60
-            t /= 60
+            t //= 60
             hours = t % 24
-            t /= 24
+            t //= 24
             if t > 0:
                 days = t
                 return '%dd %02d:%02d:%02d' % (days, hours, minutes, seconds)
@@ -253,23 +253,25 @@ def finish(self):
         self.current_item = None
         self.finished = True
 
-    def next(self):
+    def generator(self):
+        """
+        Returns a generator which yields the items added to the bar during
+        construction, and updates the progress bar *after* the yielded block
+        returns.
+        """
+        if not self.entered:
+            raise RuntimeError('You need to use progress bars in a with block.')
+
         if self.is_hidden:
-            return next(self.iter)
-        try:
-            rv = next(self.iter)
-            self.current_item = rv
-        except StopIteration:
+            for rv in self.iter:
+                yield rv
+        else:
+            for rv in self.iter:
+                self.current_item = rv
+                yield rv
+                self.update(1)
             self.finish()
             self.render_progress()
-            raise StopIteration()
-        else:
-            self.update(1)
-            return rv
-
-    if not PY2:
-        __next__ = next
-        del next
 
 
 def pager(text, color=None):

tests/test_termui.py

@@ -1,4 +1,5 @@
 import click
+import time
 
 
 def test_progressbar_strip_regression(runner, monkeypatch):
@@ -69,3 +70,41 @@ def test_secho(runner):
         click.secho(None, nl=False)
         bytes = out.getvalue()
         assert bytes == b''
+
+
+def test_progressbar_yields_all_items(runner):
+    with click.progressbar(range(3)) as progress:
+        assert len(list(progress)) == 3
+
+
+def test_progressbar_update(runner, monkeypatch):
+    class FakeClock(object):
+        def __init__(self):
+            self.now = time.time()
+
+        def advance_time(self, seconds=1):
+            self.now += seconds
+
+        def time(self):
+            return self.now
+
+    fake_clock = FakeClock()
+
+    @click.command()
+    def cli():
+        with click.progressbar(range(4)) as progress:
+            for _ in progress:
+                fake_clock.advance_time()
+                print("")
+
+    monkeypatch.setattr(time, 'time', fake_clock.time)
+    monkeypatch.setattr(click._termui_impl, 'isatty', lambda _: True)
+    output = runner.invoke(cli, []).output
+
+    lines = [line for line in output.split('\n') if '[' in line]
+
+    assert '  0%' in lines[0]
+    assert ' 25%  00:00:03' in lines[1]
+    assert ' 50%  00:00:02' in lines[2]
+    assert ' 75%  00:00:01' in lines[3]
+    assert '100%          ' in lines[4]