fix __pretty__ get (#52)

* fix __pretty__ get

needs tests

* catch errors in pretty print

Author: samuelcolvin

devtools/debug.py

@@ -42,13 +42,22 @@ def str(self, highlight=False) -> str:
         s = ''
         if self.name:
             s = sformat(self.name, sformat.blue, apply=highlight) + ': '
-        s += pformat(self.value, indent=4, highlight=highlight)
-        suffix = (
-            ' ({0.value.__class__.__name__}) {1}'
-            .format(self, ' '.join('{}={}'.format(k, v) for k, v in self.extra))
-            .rstrip(' ')  # trailing space if extra is empty
+
+        suffix = sformat(
+            ' ({.value.__class__.__name__}){}'.format(self, ''.join(' {}={}'.format(k, v) for k, v in self.extra)),
+            sformat.dim,
+            apply=highlight
         )
-        s += sformat(suffix, sformat.dim, apply=highlight)
+        try:
+            s += pformat(self.value, indent=4, highlight=highlight)
+        except Exception as exc:
+            s += '{!r}{}\n    {}'.format(
+                self.value,
+                suffix,
+                sformat('!!! error pretty printing value: {!r}'.format(exc), sformat.yellow, apply=highlight),
+            )
+        else:
+            s += suffix
         return s
 
     def __str__(self) -> str:

devtools/prettier.py

@@ -1,6 +1,7 @@
 import io
 import os
 import textwrap
+import warnings
 from collections import OrderedDict
 from collections.abc import Generator
 from typing import Any, Union
@@ -89,10 +90,13 @@ def _format(self, value: Any, indent_current: int, indent_first: bool):
             self._stream.write(indent_current * self._c)
 
         pretty_func = getattr(value, '__pretty__', None)
-        if pretty_func and not isinstance(value, MockCall):
+        if pretty_func and callable(pretty_func) and not isinstance(value, MockCall):
             try:
                 gen = pretty_func(fmt=fmt, skip_exc=SkipPretty)
                 self._render_pretty(gen, indent_current)
+            except TypeError as e:
+                if e.args != ("__pretty__() missing 1 required positional argument: 'self'",):
+                    raise
             except SkipPretty:
                 pass
             else:

tests/test_custom_pretty.py

@@ -47,3 +47,19 @@ def __pretty__(self, fmt, **kwargs):
     my_cls = CustomCls()
     v = pformat(my_cls)
     assert v == "'xxx'123"
+
+
+def test_pretty_not_func():
+    class Foobar:
+        __pretty__ = 1
+
+    assert '<locals>.Foobar object' in pformat(Foobar())
+
+
+def test_pretty_class():
+    class Foobar:
+        def __pretty__(self, fmt, **kwargs):
+            yield 'xxx'
+
+    assert pformat(Foobar()) == 'xxx'
+    assert pformat(Foobar).endswith(".test_pretty_class.<locals>.Foobar'>")

tests/test_main.py

@@ -95,6 +95,7 @@ def test_small_call_frame_warning():
         2,
         3,
     )
+    print(str(v))
     assert re.sub(r':\d{2,}', ':<line no>', str(v)) == (
         "tests/test_main.py:<line no> test_small_call_frame_warning "
         "(error passing code, found <class '_ast.Tuple'> not Call)\n"
@@ -239,3 +240,19 @@ def test_starred_kwargs():
         '    foo: 1 (int)',
         '    bar: 2 (int)',
     }
+
+
+def test_pretty_error():
+    class BadPretty:
+        def __getattr__(self, item):
+            raise RuntimeError('this is an error')
+
+    b = BadPretty()
+    v = debug.format(b)
+    s = re.sub(r':\d{2,}', ':<line no>', str(v))
+    s = re.sub(r'0x[0-9a-f]+', '0x000', s)
+    assert s == (
+        "tests/test_main.py:<line no> test_pretty_error\n"
+        "    b: <tests.test_main.test_pretty_error.<locals>.BadPretty object at 0x000> (BadPretty)\n"
+        "    !!! error pretty printing value: RuntimeError('this is an error')"
+    )