Repository: mahmoud/boltons

Issue:
research should accept remap args
https://github.com/mahmoud/boltons/blob/6a363e6c4837a2cca606eba5903ea6f4ae83d745/boltons/iterutils.py#L1355

for the case where you have you custom `enter`.

Discussion:
@mahmoud: Interesting, sure, I guess I could see a custom `enter` if you were trying to traverse iterables which `default_enter` doesn't support.

Just looking at this, I think I would change `research` to use `visit` instead of `enter` and then allow a custom `enter` to be passed. But I don't think there's much value to a custom `visit` or `exit`, can you think of any?@majidaldo: > Interesting, sure, I guess I could see a custom `enter` if you were trying to traverse iterables which `default_enter` doesn't support.
> 
> Just looking at this, I think I would change `research` to use `visit` instead of `enter` and then allow a custom `enter` to be passed. But I don't think there's much value to a custom `visit` or `exit`, can you think of any?

Didn't understand "and then allow a custom `enter` to be passed".  The case that I had in mind, is when the object at the *root* is 'custom'... you need a way to compose/decompose.

```{python}
 from types import SimpleNamespace as NS
 NS(
        a='a',
        b='b',
            c=NS(aa='aa') )
```
@mahmoud: @majidaldo just pushed a PR (#372) that I think is closer to what you might have expected. check out the test to see it in action with SimpleNamespace.

Solution patch:
diff --git a/boltons/iterutils.py b/boltons/iterutils.py
index fb3d366..e0a5b90 100644
--- a/boltons/iterutils.py
+++ b/boltons/iterutils.py
@@ -165,15 +165,15 @@ def split_iter(src, sep=None, maxsplit=None):
         sep_func = sep
     elif not is_scalar(sep):
         sep = frozenset(sep)
-        sep_func = lambda x: x in sep
+        def sep_func(x): return x in sep
     else:
-        sep_func = lambda x: x == sep
+        def sep_func(x): return x == sep
 
     cur_group = []
     split_count = 0
     for s in src:
         if maxsplit is not None and split_count >= maxsplit:
-            sep_func = lambda x: False
+            def sep_func(x): return False
         if sep_func(s):
             if sep is None and not cur_group:
                 # If sep is none, str.split() "groups" separators
@@ -229,7 +229,7 @@ def rstrip(iterable, strip_value=None):
     ['Foo', 'Bar']
 
     """
-    return list(rstrip_iter(iterable,strip_value))
+    return list(rstrip_iter(iterable, strip_value))
 
 
 def rstrip_iter(iterable, strip_value=None):
@@ -253,7 +253,7 @@ def rstrip_iter(iterable, strip_value=None):
                 else:
                     broken = True
                     break
-            if not broken: # Return to caller here because the end of the
+            if not broken:  # Return to caller here because the end of the
                 return     # iterator has been reached
             yield from cache
         yield i
@@ -268,10 +268,10 @@ def strip(iterable, strip_value=None):
     ['Foo', 'Bar', 'Bam']
 
     """
-    return list(strip_iter(iterable,strip_value))
+    return list(strip_iter(iterable, strip_value))
 
 
-def strip_iter(iterable,strip_value=None):
+def strip_iter(iterable, strip_value=None):
     """Strips values from the beginning and end of an iterable. Stripped items
     will match the value of the argument strip_value. Functionality is
     analogous to that of the method str.strip. Returns a generator.
@@ -280,7 +280,7 @@ def strip_iter(iterable,strip_value=None):
     ['Foo', 'Bar', 'Bam']
 
     """
-    return rstrip_iter(lstrip_iter(iterable,strip_value),strip_value)
+    return rstrip_iter(lstrip_iter(iterable, strip_value), strip_value)
 
 
 def chunked(src, size, count=None, **kw):
@@ -340,11 +340,12 @@ def chunked_iter(src, size, **kw):
         raise ValueError('got unexpected keyword arguments: %r' % kw.keys())
     if not src:
         return
-    postprocess = lambda chk: chk
+
+    def postprocess(chk): return chk
     if isinstance(src, (str, bytes)):
-        postprocess = lambda chk, _sep=type(src)(): _sep.join(chk)
+        def postprocess(chk, _sep=type(src)()): return _sep.join(chk)
         if isinstance(src, bytes):
-            postprocess = lambda chk: bytes(chk)
+            def postprocess(chk): return bytes(chk)
     src_iter = iter(src)
     while True:
         cur_chunk = list(itertools.islice(src_iter, size))
@@ -385,15 +386,19 @@ def chunk_ranges(input_size, chunk_size, input_offset=0, overlap_size=0, align=F
     >>> list(chunk_ranges(input_offset=3, input_size=15, chunk_size=5, overlap_size=1, align=True))
     [(3, 5), (4, 9), (8, 13), (12, 17), (16, 18)]
     """
-    input_size = _validate_positive_int(input_size, 'input_size', strictly_positive=False)
+    input_size = _validate_positive_int(
+        input_size, 'input_size', strictly_positive=False)
     chunk_size = _validate_positive_int(chunk_size, 'chunk_size')
-    input_offset = _validate_positive_int(input_offset, 'input_offset', strictly_positive=False)
-    overlap_size = _validate_positive_int(overlap_size, 'overlap_size', strictly_positive=False)
+    input_offset = _validate_positive_int(
+        input_offset, 'input_offset', strictly_positive=False)
+    overlap_size = _validate_positive_int(
+        overlap_size, 'overlap_size', strictly_positive=False)
 
     input_stop = input_offset + input_size
 
     if align:
-        initial_chunk_len = chunk_size - input_offset % (chunk_size - overlap_size)
+        initial_chunk_len = chunk_size - \
+            input_offset % (chunk_size - overlap_size)
         if initial_chunk_len != overlap_size:
             yield (input_offset, min(input_offset + initial_chunk_len, input_stop))
             if input_offset + initial_chunk_len >= input_stop:
@@ -479,7 +484,7 @@ def windowed_iter(src, size, fill=_UNSET):
 
     With *fill* set, the iterator always yields a number of windows
     equal to the length of the *src* iterable.
-    
+
     >>> windowed(range(4), 3, fill=None)
     [(0, 1, 2), (1, 2, 3), (2, 3, None), (3, None, None)]
 
@@ -495,9 +500,9 @@ def windowed_iter(src, size, fill=_UNSET):
         except StopIteration:
             return zip([])
         return zip(*tees)
-    
+
     for i, t in enumerate(tees):
-        for _ in range(i):  
+        for _ in range(i):
             try:
                 next(t)
             except StopIteration:
@@ -505,7 +510,6 @@ def windowed_iter(src, size, fill=_UNSET):
     return zip_longest(*tees, fillvalue=fill)
 
 
-
 def xfrange(stop, start=None, step=1.0):
     """Same as :func:`frange`, but generator-based instead of returning a
     list.
@@ -726,21 +730,21 @@ def bucketize(src, key=bool, value_transform=None, key_filter=None):
         src = zip(key, src)
 
     if isinstance(key, str):
-        key_func = lambda x: getattr(x, key, x)
+        def key_func(x): return getattr(x, key, x)
     elif callable(key):
         key_func = key
     elif isinstance(key, list):
-        key_func = lambda x: x[0]
+        def key_func(x): return x[0]
     else:
         raise TypeError('expected key to be callable or a string or a list')
 
     if value_transform is None:
-        value_transform = lambda x: x
+        def value_transform(x): return x
     if not callable(value_transform):
         raise TypeError('expected callable value transform function')
     if isinstance(key, list):
         f = value_transform
-        value_transform=lambda x: f(x[1])
+        def value_transform(x): return f(x[1])
 
     ret = {}
     for val in src:
@@ -807,11 +811,11 @@ def unique_iter(src, key=None):
     if not is_iterable(src):
         raise TypeError('expected an iterable, not %r' % type(src))
     if key is None:
-        key_func = lambda x: x
+        def key_func(x): return x
     elif callable(key):
         key_func = key
     elif isinstance(key, str):
-        key_func = lambda x: getattr(x, key, x)
+        def key_func(x): return getattr(x, key, x)
     else:
         raise TypeError('"key" expected a string or callable, not %r' % key)
     seen = set()
@@ -862,7 +866,7 @@ def redundant(src, key=None, groups=False):
     elif callable(key):
         key_func = key
     elif isinstance(key, (str, bytes)):
-        key_func = lambda x: getattr(x, key, x)
+        def key_func(x): return getattr(x, key, x)
     else:
         raise TypeError('"key" expected a string or callable, not %r' % key)
     seen = {}  # key to first seen item
@@ -964,6 +968,7 @@ def flatten_iter(iterable):
         else:
             yield item
 
+
 def flatten(iterable):
     """``flatten()`` returns a collapsed list of all the elements from
     *iterable* while collapsing any nested iterables.
@@ -1006,6 +1011,7 @@ def default_visit(path, key, value):
     # print('visit(%r, %r, %r)' % (path, key, value))
     return key, value
 
+
 # enable the extreme: monkeypatching iterutils with a different default_visit
 _orig_default_visit = default_visit
 
@@ -1128,6 +1134,9 @@ def remap(root, visit=default_visit, enter=default_enter, exit=default_exit,
             callable. When set to ``False``, remap ignores any errors
             raised by the *visit* callback. Items causing exceptions
             are kept. See examples for more details.
+        trace (bool): Pass ``trace=True`` to print out the entire
+            traversal. Or pass a tuple of ``'visit'``, ``'enter'``,
+            or ``'exit'`` to print only the selected events.
 
     remap is designed to cover the majority of cases with just the
     *visit* callable. While passing in multiple callables is very
@@ -1156,6 +1165,15 @@ def remap(root, visit=default_visit, enter=default_enter, exit=default_exit,
     if not callable(exit):
         raise TypeError('exit expected callable, not: %r' % exit)
     reraise_visit = kwargs.pop('reraise_visit', True)
+    trace = kwargs.pop('trace', ())
+    if trace is True:
+        trace = ('visit', 'enter', 'exit')
+    elif isinstance(trace, str):
+        trace = (trace,)
+    if not isinstance(trace, (tuple, list, set)):
+        raise TypeError('trace expected tuple of event names, not: %r' % trace)
+    trace_enter, trace_exit, trace_visit = 'enter' in trace, 'exit' in trace, 'visit' in trace
+
     if kwargs:
         raise TypeError('unexpected keyword arguments: %r' % kwargs.keys())
 
@@ -1168,14 +1186,23 @@ def remap(root, visit=default_visit, enter=default_enter, exit=default_exit,
             key, new_parent, old_parent = value
             id_value = id(old_parent)
             path, new_items = new_items_stack.pop()
+            if trace_exit:
+                print(' .. remap exit:', path, '-', key, '-',
+                      old_parent, '-', new_parent, '-', new_items)
             value = exit(path, key, old_parent, new_parent, new_items)
+            if trace_exit:
+                print(' .. remap exit result:', value)
             registry[id_value] = value
             if not new_items_stack:
                 continue
         elif id_value in registry:
             value = registry[id_value]
         else:
+            if trace_enter:
+                print(' .. remap enter:', path, '-', key, '-', value)
             res = enter(path, key, value)
+            if trace_enter:
+                print(' .. remap enter result:', res)
             try:
                 new_parent, new_items = res
             except TypeError:
@@ -1191,21 +1218,29 @@ def remap(root, visit=default_visit, enter=default_enter, exit=default_exit,
                 stack.append((_REMAP_EXIT, (key, new_parent, value)))
                 if new_items:
                     stack.extend(reversed(list(new_items)))
+                if trace_enter:
+                    print(' .. remap stack size now:', len(stack))
                 continue
         if visit is _orig_default_visit:
             # avoid function call overhead by inlining identity operation
             visited_item = (key, value)
         else:
             try:
+                if trace_visit:
+                    print(' .. remap visit:', path, '-', key, '-', value)
                 visited_item = visit(path, key, value)
             except Exception:
                 if reraise_visit:
                     raise
                 visited_item = True
             if visited_item is False:
+                if trace_visit:
+                    print(' .. remap visit result: <drop>')
                 continue  # drop
             elif visited_item is True:
                 visited_item = (key, value)
+            if trace_visit:
+                print(' .. remap visit result:', visited_item)
             # TODO: typecheck?
             #    raise TypeError('expected (key, value) from visit(),'
             #                    ' not: %r' % visited_item)
@@ -1221,6 +1256,7 @@ class PathAccessError(KeyError, IndexError, TypeError):
     representing what can occur when looking up a path in a nested
     object.
     """
+
     def __init__(self, exc, seg, path):
         self.exc = exc
         self.seg = seg
@@ -1296,7 +1332,7 @@ def get_path(root, path, default=_UNSET):
     return cur
 
 
-def research(root, query=lambda p, k, v: True, reraise=False):
+def research(root, query=lambda p, k, v: True, reraise=False, enter=default_enter):
     """The :func:`research` function uses :func:`remap` to recurse over
     any data nested in *root*, and find values which match a given
     criterion, specified by the *query* callable.
@@ -1343,16 +1379,16 @@ def research(root, query=lambda p, k, v: True, reraise=False):
     if not callable(query):
         raise TypeError('query expected callable, not: %r' % query)
 
-    def enter(path, key, value):
+    def _enter(path, key, value):
         try:
             if query(path, key, value):
                 ret.append((path + (key,), value))
         except Exception:
             if reraise:
                 raise
-        return default_enter(path, key, value)
+        return enter(path, key, value)
 
-    remap(root, enter=enter)
+    remap(root, enter=_enter)
     return ret
 
 
@@ -1383,6 +1419,7 @@ class GUIDerator:
     detect a fork on next iteration and reseed accordingly.
 
     """
+
     def __init__(self, size=24):
         self.size = size
         if size < 20 or size > 36:
@@ -1495,13 +1532,16 @@ def soft_sorted(iterable, first=None, last=None, key=None, reverse=False):
     last = last or []
     key = key or (lambda x: x)
     seq = list(iterable)
-    other = [x for x in seq if not ((first and key(x) in first) or (last and key(x) in last))]
+    other = [x for x in seq if not (
+        (first and key(x) in first) or (last and key(x) in last))]
     other.sort(key=key, reverse=reverse)
 
     if first:
-        first = sorted([x for x in seq if key(x) in first], key=lambda x: first.index(key(x)))
+        first = sorted([x for x in seq if key(x) in first],
+                       key=lambda x: first.index(key(x)))
     if last:
-        last = sorted([x for x in seq if key(x) in last], key=lambda x: last.index(key(x)))
+        last = sorted([x for x in seq if key(x) in last],
+                      key=lambda x: last.index(key(x)))
     return first + other + last
 
 
@@ -1536,7 +1576,7 @@ def untyped_sorted(iterable, key=None, reverse=False):
                 ret = obj < other
             except TypeError:
                 ret = ((type(obj).__name__, id(type(obj)), obj)
-                        < (type(other).__name__, id(type(other)), other))
+                       < (type(other).__name__, id(type(other)), other))
             return ret
 
     if key is not None and not callable(key):
@@ -1545,6 +1585,7 @@ def untyped_sorted(iterable, key=None, reverse=False):
 
     return sorted(iterable, key=_Wrapper, reverse=reverse)
 
+
 """
 May actually be faster to do an isinstance check for a str path
 


Test patch:
diff --git a/tests/test_iterutils.py b/tests/test_iterutils.py
index cbe52bb..f661f68 100644
--- a/tests/test_iterutils.py
+++ b/tests/test_iterutils.py
@@ -396,6 +396,28 @@ def test_research():
     assert research(root, broken_query) == []
 
 
+def test_research_custom_enter():
+    # see #368
+    from types import SimpleNamespace as NS
+    root = NS(
+        a='a',
+        b='b',
+        c=NS(aa='aa') )
+
+    def query(path, key, value):
+        return value.startswith('a')
+    
+    def custom_enter(path, key, value):
+        if isinstance(value, NS):
+            return [], value.__dict__.items()
+        return default_enter(path, key, value)
+
+    with pytest.raises(TypeError):
+        research(root, query)
+    assert research(root, query, enter=custom_enter) == [(('a',), 'a'), (('c', 'aa'), 'aa')]
+
+
+
 def test_backoff_basic():
     from boltons.iterutils import backoff