Add pretty print debug

docs/src/markdown/about/changelog.md

@@ -8,6 +8,7 @@
   ignore empty ones. As the scraping environment is different that a browser environment, it was chosen not to
   aggressively forgive bad syntax and invalid features to ensure the user is alerted that their program may not perform
   as expected.
+- **NEW**: Add support to output a pretty print format of a compiled `SelectorList` for debug purposes.
 
 ## 2.2.1
 

docs/src/markdown/about/development.md

@@ -193,6 +193,63 @@ object that may chain other `SelectorLists` objects depending on the complexity
 a selector list, then you will get multiple `Selector` objects (one for each compound selector in the list) which in
 turn may chain other `Selector` objects.
 
+To view the selector list in in a compiled object for debugging purposes, one can access it via `SoupSieve.selectors`,
+though it is recommended to pretty print them:
+
+```pycon3
+>>> import soupsieve as sv
+>>> sv.compile('this > that.class[name=value]').selectors.pretty()
+SelectorList(
+    selectors=(
+        Selector(
+            tag=SelectorTag(
+                name='that',
+                prefix=None),
+            ids=(),
+            classes=(
+                'class',
+                ),
+            attributes=(
+                SelectorAttribute(
+                    attribute='name',
+                    prefix='',
+                    pattern=re.compile(
+                        '^value$'),
+                    xml_type_pattern=None),
+                ),
+            nth=(),
+            selectors=(),
+            relation=SelectorList(
+                selectors=(
+                    Selector(
+                        tag=SelectorTag(
+                            name='this',
+                            prefix=None),
+                        ids=(),
+                        classes=(),
+                        attributes=(),
+                        nth=(),
+                        selectors=(),
+                        relation=SelectorList(
+                            selectors=(),
+                            is_not=False,
+                            is_html=False),
+                        rel_type='>',
+                        contains=(),
+                        lang=(),
+                        flags=0),
+                    ),
+                is_not=False,
+                is_html=False),
+            rel_type=None,
+            contains=(),
+            lang=(),
+            flags=0),
+        ),
+    is_not=False,
+    is_html=False)
+```
+
 ### `SelectorList`
 
 ```py3

soupsieve/css_types.py

@@ -1,6 +1,7 @@
 """CSS selector structure items."""
 import copyreg
 from collections.abc import Hashable, Mapping
+from .pretty import pretty
 
 __all__ = (
     'Selector',
@@ -80,11 +81,16 @@ def __repr__(self):  # pragma: no cover
         """Representation."""
 
         return "{}({})".format(
-            self.__base__(), ', '.join(["{}={!r}".format(k, getattr(self, k)) for k in self.__slots__[:-1]])
+            self.__class__.__name__, ', '.join(["{}={!r}".format(k, getattr(self, k)) for k in self.__slots__[:-1]])
         )
 
     __str__ = __repr__
 
+    def pretty(self):  # pragma: no cover
+        """Pretty print."""
+
+        print(pretty(self))
+
 
 class ImmutableDict(Mapping):
     """Hashable, immutable dictionary."""

soupsieve/pretty.py

@@ -0,0 +1,136 @@
+"""
+Format a pretty string of a `SoupSieve` object for easy debugging.
+
+This won't necessarily support all types and such, and definitely
+not support custom outputs.
+
+It is mainly geared towards our types as the `SelectorList`
+object is a beast to look at without some indentation and newlines.
+The format and various output types is fairly known (though it
+hasn't been tested extensively to make sure we aren't missing corners).
+
+Example:
+
+```
+>>> import soupsieve as sv
+>>> sv.compile('this > that.class[name=value]').selectors.pretty()
+SelectorList(
+    selectors=(
+        Selector(
+            tag=SelectorTag(
+                name='that',
+                prefix=None),
+            ids=(),
+            classes=(
+                'class',
+                ),
+            attributes=(
+                SelectorAttribute(
+                    attribute='name',
+                    prefix='',
+                    pattern=re.compile(
+                        '^value$'),
+                    xml_type_pattern=None),
+                ),
+            nth=(),
+            selectors=(),
+            relation=SelectorList(
+                selectors=(
+                    Selector(
+                        tag=SelectorTag(
+                            name='this',
+                            prefix=None),
+                        ids=(),
+                        classes=(),
+                        attributes=(),
+                        nth=(),
+                        selectors=(),
+                        relation=SelectorList(
+                            selectors=(),
+                            is_not=False,
+                            is_html=False),
+                        rel_type='>',
+                        contains=(),
+                        lang=(),
+                        flags=0),
+                    ),
+                is_not=False,
+                is_html=False),
+            rel_type=None,
+            contains=(),
+            lang=(),
+            flags=0),
+        ),
+    is_not=False,
+    is_html=False)
+```
+"""
+import re
+
+RE_CLASS = re.compile(r'(?i)[a-z_][_a-z\d\.]+\(')
+RE_PARAM = re.compile(r'(?i)[_a-z][_a-z\d]+=')
+RE_EMPTY = re.compile(r'\(\)|\[\]|\{\}')
+RE_LSTRT = re.compile(r'\[')
+RE_DSTRT = re.compile(r'\{')
+RE_TSTRT = re.compile(r'\(')
+RE_LEND = re.compile(r'\]')
+RE_DEND = re.compile(r'\}')
+RE_TEND = re.compile(r'\)')
+RE_INT = re.compile(r'\d+')
+RE_KWORD = re.compile(r'(?i)[_a-z][_a-z\d]+')
+RE_DQSTR = re.compile(r'"(?:\\.|[^"\\])*"')
+RE_SQSTR = re.compile(r"'(?:\\.|[^'\\])*'")
+RE_SEP = re.compile(r'\s*(,)\s*')
+RE_DSEP = re.compile(r'\s*(:)\s*')
+
+TOKENS = {
+    'class': RE_CLASS,
+    'param': RE_PARAM,
+    'empty': RE_EMPTY,
+    'lstrt': RE_LSTRT,
+    'dstrt': RE_DSTRT,
+    'tstrt': RE_TSTRT,
+    'lend': RE_LEND,
+    'dend': RE_DEND,
+    'tend': RE_TEND,
+    'sqstr': RE_SQSTR,
+    'sep': RE_SEP,
+    'dsep': RE_DSEP,
+    'int': RE_INT,
+    'kword': RE_KWORD,
+    'dqstr': RE_DQSTR
+}
+
+
+def pretty(obj):  # pragma: no cover
+    """Make the object output string pretty."""
+
+    sel = str(obj)
+    index = 0
+    end = len(sel) - 1
+    indent = 0
+    output = []
+
+    while index <= end:
+        m = None
+        for k, v in TOKENS.items():
+            m = v.match(sel, index)
+
+            if m:
+                name = k
+                index = m.end(0)
+                if name in ('class', 'lstrt', 'dstrt', 'tstrt'):
+                    indent += 4
+                    output.append('{}\n{}'.format(m.group(0), " " * indent))
+                elif name in ('param', 'int', 'kword', 'sqstr', 'dqstr', 'empty'):
+                    output.append(m.group(0))
+                elif name in ('lend', 'dend', 'tend'):
+                    indent -= 4
+                    output.append(m.group(0))
+                elif name in ('sep',):
+                    output.append('{}\n{}'.format(m.group(1), " " * indent))
+                elif name in ('dsep',):
+                    output.append('{} '.format(m.group(1)))
+                break
+
+    return ''.join(output)