Merge pull request #2065 from Zac-HD/lark-fix

Fix for newest Lark parser

hypothesis-python/RELEASE.rst

@@ -3,3 +3,6 @@ RELEASE_TYPE: patch
 This patch tidies up the repr of several ``settings``-related objects,
 at runtime and in the documentation, and deprecates the undocumented
 edge case that ``phases=None`` was treated like ``phases=tuple(Phase)``.
+
+It *also* fixes :func:`~hypothesis.extra.lark.from_lark` with
+:pypi:`lark 0.7.2 <lark-parser>` and later.

hypothesis-python/scripts/basic-test.sh

@@ -33,6 +33,8 @@ pip uninstall -y dpcontracts
 
 pip install ".[lark]"
 $PYTEST tests/lark/
+pip install lark-parser==0.7.1
+$PYTEST tests/lark/
 pip uninstall -y lark-parser
 
 if [ "$(python -c 'import sys; print(sys.version_info[:2] in ((2, 7), (3, 6)))')" = "False" ] ; then

hypothesis-python/src/hypothesis/extra/lark.py

@@ -44,6 +44,7 @@
 
 import hypothesis._strategies as st
 from hypothesis.errors import InvalidArgument
+from hypothesis.internal.compat import getfullargspec
 from hypothesis.internal.conjecture.utils import calc_label_from_name
 from hypothesis.internal.validation import check_type
 from hypothesis.searchstrategy import SearchStrategy
@@ -78,9 +79,15 @@ def __init__(self, grammar, start=None):
         check_type(lark.lark.Lark, grammar, "grammar")
         if start is None:
             start = grammar.options.start
+        if not isinstance(start, list):
+            start = [start]
         self.grammar = grammar
 
-        terminals, rules, ignore_names = grammar.grammar.compile()
+        if "start" in getfullargspec(grammar.grammar.compile).args:
+            terminals, rules, ignore_names = grammar.grammar.compile(start)
+        else:  # pragma: no cover
+            # This branch is to support lark <= 0.7.1, without the start argument.
+            terminals, rules, ignore_names = grammar.grammar.compile()
 
         self.names_to_symbols = {}
 
@@ -91,7 +98,7 @@ def __init__(self, grammar, start=None):
         for t in terminals:
             self.names_to_symbols[t.name] = Terminal(t.name)
 
-        self.start = self.names_to_symbols[start]
+        self.start = st.sampled_from([self.names_to_symbols[s] for s in start])
 
         self.ignored_symbols = (
             st.sampled_from([self.names_to_symbols[n] for n in ignore_names])
@@ -120,7 +127,8 @@ def __init__(self, grammar, start=None):
 
     def do_draw(self, data):
         state = DrawState()
-        self.draw_symbol(data, self.start, state)
+        start = data.draw(self.start)
+        self.draw_symbol(data, start, state)
         return u"".join(state.result)
 
     def rule_label(self, name):

requirements/coverage.txt

@@ -5,7 +5,7 @@
 #    pip-compile --output-file=requirements/coverage.txt requirements/coverage.in
 #
 coverage==4.5.4
-lark-parser==0.7.1
+lark-parser==0.7.2
 numpy==1.17.0
 pandas==0.25.0
 python-dateutil==2.8.0    # via pandas