Fixed IndentedBlock

1 files changed, 80 insertions, 0 deletions

diff --git a/pyparsing/core.py b/pyparsing/core.py
index 775c7b4..9370101 100644
--- a/pyparsing/core.py
+++ b/pyparsing/core.py
@@ -3753,6 +3753,24 @@ class And(ParseExpression):
                 self.exprs = [e for e in self.exprs if e is not None]
 
         super().streamline()
+
+        # link any IndentedBlocks to the prior expression
+        for prev, cur in zip(self.exprs, self.exprs[1:]):
+            # traverse cur or any first embedded expr of cur looking for an IndentedBlock
+            # (but watch out for recursive grammar)
+            seen = set()
+            while cur:
+                if id(cur) in seen:
+                    break
+                seen.add(id(cur))
+                if isinstance(cur, IndentedBlock):
+                    prev.add_parse_action(
+                        lambda s, l, t: setattr(cur, "parent_anchor", col(l, s))
+                    )
+                    break
+                subs = cur.recurse()
+                cur = next(iter(subs), None)
+
         self.mayReturnEmpty = all(e.mayReturnEmpty for e in self.exprs)
         return self
 
@@ -4305,6 +4323,68 @@ class ParseElementEnhance(ParserElement):
     leaveWhitespace = leave_whitespace
 
 
+class IndentedBlock(ParseElementEnhance):
+    """
+    Expression to match one or more expressions at a given indentation level.
+    Useful for parsing text where structure is implied by indentation (like Python source code).
+    """
+
+    class _Indent(Empty):
+        def __init__(self, ref_col: int):
+            super().__init__()
+            self.errmsg = "expected indent at column {}".format(ref_col)
+            self.add_condition(lambda s, l, t: col(l, s) == ref_col)
+
+    class _IndentGreater(Empty):
+        def __init__(self, ref_col: int):
+            super().__init__()
+            self.errmsg = "expected indent at column greater than {}".format(ref_col)
+            self.add_condition(lambda s, l, t: col(l, s) > ref_col)
+
+    def __init__(self, expr: ParserElement, *, recursive: bool = False, grouped=True):
+        super().__init__(expr, savelist=True)
+        # if recursive:
+        #     raise NotImplementedError("IndentedBlock with recursive is not implemented")
+        self._recursive = recursive
+        self._grouped = grouped
+        self.parent_anchor = 1
+
+    def parseImpl(self, instring, loc, doActions=True):
+        # advance parse position to non-whitespace by using an Empty()
+        # this should be the column to be used for all subsequent indented lines
+        anchor_loc = Empty().preParse(instring, loc)
+
+        # see if self.expr matches at the current location - if not it will raise an exception
+        # and no further work is necessary
+        self.expr.try_parse(instring, anchor_loc, doActions)
+
+        indent_col = col(anchor_loc, instring)
+        peer_detect_expr = self._Indent(indent_col)
+
+        inner_expr = Empty() + peer_detect_expr + self.expr
+        if self._recursive:
+            sub_indent = self._IndentGreater(indent_col)
+            nested_block = IndentedBlock(
+                self.expr, recursive=self._recursive, grouped=self._grouped
+            )
+            nested_block.set_debug(self.debug)
+            nested_block.parent_anchor = indent_col
+            inner_expr += Opt(sub_indent + nested_block)
+
+        inner_expr.set_name(f"inner {hex(id(inner_expr))[-4:].upper()}@{indent_col}")
+        block = OneOrMore(inner_expr)
+
+        trailing_undent = self._Indent(self.parent_anchor) | StringEnd()
+
+        if self._grouped:
+            wrapper = Group
+        else:
+            wrapper = lambda expr: expr
+        return (wrapper(block) + Optional(trailing_undent)).parseImpl(
+            instring, anchor_loc, doActions
+        )
+
+
 class AtStringStart(ParseElementEnhance):
     """Matches if expression matches at the beginning of the parse
     string::