Inlcude zeros in SHACL regex bounds

We included the regex pattern as-is from the input. Instead, with this
patch, we parse it from the input and re-render it into the canonical
form so that many more regex engines can work with it.

For example, in the input, we omit the minimum bound 0 (*e.g.*,
``{,4}``), which breaks with the Java regex engine beneath
the SHACL validator. Now, the pattern is correctly rendered with an
explicit 0 (``{0,4}``).

Discovered in [aas-core-meta issue 342].

[aas-core-meta issue 342]: aas-core-works/aas-core-meta#342

aas_core_codegen/rdf_shacl/shacl.py

@@ -7,6 +7,7 @@
 
 from aas_core_codegen import intermediate, specific_implementations, infer_for_schema
 from aas_core_codegen.common import Stripped, Error, assert_never, Identifier
+from aas_core_codegen.parse import retree as parse_retree
 from aas_core_codegen.rdf_shacl import (
     naming as rdf_shacl_naming,
     common as rdf_shacl_common,
@@ -214,7 +215,33 @@ def _define_property_shape(
     # region Define patterns
 
     for pattern_constraint in pattern_constraints:
-        pattern_literal = rdf_shacl_common.string_literal(pattern_constraint.pattern)
+        # NOTE (mristin):
+        # We need to render the regular expression so that the pattern appears in
+        # the canonical form. The original pattern in the specification might be written
+        # in Python dialect, which does not translate directly to many Regex Engines.
+        #
+        # For example, repetition bounds can be given with 0 omitted (*e.g.*, ``{,4}``),
+        # while SHACL and Java need an explicit zero (``{0, 4}``). Our standard renderer
+        # puts an explicit zero.
+
+        regex, parse_error = parse_retree.parse([pattern_constraint.pattern])
+        if parse_error is not None:
+            return None, Error(
+                prop.parsed.node,
+                f"(mristin): "
+                f"The pattern could not be parsed: {pattern_constraint.pattern}",
+            )
+        assert regex is not None
+
+        rendered_pattern = parse_retree.render(regex)
+
+        assert len(rendered_pattern) == 1 and isinstance(rendered_pattern[0], str), (
+            "Expected strictly only a string output from rendering "
+            f"a string pattern (*e.g.*, no FormattedValues), "
+            f"but got: {rendered_pattern}"
+        )
+
+        pattern_literal = rdf_shacl_common.string_literal(rendered_pattern[0])
 
         stmts.append(Stripped(f"sh:pattern {pattern_literal} ;"))