fallback catch all exceptions (#148)

Author: mandel

src/pdl/pdl_interpreter.py

@@ -318,7 +318,20 @@ def step_advanced_block(
         result, background, scope, trace = yield from step_block_body(
             state, scope, block, loc
         )
-    except PDLRuntimeError as exc:
+        trace = trace.model_copy(update={"result": result})
+        if block.parser is not None:
+            result = parse_result(block.parser, result)
+        if block.spec is not None and not isinstance(block, FunctionBlock):
+            errors = type_check_spec(result, block.spec, block.location)
+            if len(errors) > 0:
+                message = "Type errors during spec checking:\n" + "\n".join(errors)
+                raise PDLRuntimeError(
+                    message,
+                    loc=loc,
+                    trace=ErrorBlock(msg=message, program=trace),
+                    fallback=result,
+                )
+    except Exception as exc:
         if block.fallback is None:
             raise exc from exc
         (
@@ -334,29 +347,19 @@ def step_advanced_block(
             scope,
             loc=loc,
         )
-    trace = trace.model_copy(update={"result": result})
-    if block.parser is not None:
-        try:
-            result = parse_result(block.parser, result)
-        except PDLRuntimeParserError as exc:
-            raise PDLRuntimeError(
-                exc.message,
-                loc=exc.loc or loc,
-                trace=ErrorBlock(msg=exc.message, program=trace, fallback=result),
-            ) from exc
+        if block.spec is not None and not isinstance(block, FunctionBlock):
+            errors = type_check_spec(result, block.spec, block.location)
+            if len(errors) > 0:
+                message = "Type errors during spec checking:\n" + "\n".join(errors)
+                raise PDLRuntimeError(  # pylint: disable=raise-missing-from
+                    message,
+                    loc=append(loc, "fallback"),
+                    trace=ErrorBlock(msg=message, program=trace),
+                    fallback=result,
+                )
     if block.assign is not None:
         var = block.assign
         scope = scope | {var: result}
-    if block.spec is not None and not isinstance(block, FunctionBlock):
-        errors = type_check_spec(result, block.spec, block.location)
-        if len(errors) > 0:
-            message = "Type errors during spec checking:\n" + "\n".join(errors)
-            raise PDLRuntimeError(
-                message,
-                loc=loc,
-                trace=ErrorBlock(msg=message, program=trace),
-                fallback=result,
-            )
     if ContributeTarget.RESULT not in block.contribute:
         result = ""
     if ContributeTarget.CONTEXT not in block.contribute:

tests/test_fallback.py

@@ -1,5 +1,13 @@
+import pytest
+
+from pdl.pdl import exec_str
 from pdl.pdl_ast import Program
-from pdl.pdl_interpreter import InterpreterState, empty_scope, process_prog
+from pdl.pdl_interpreter import (
+    InterpreterState,
+    PDLRuntimeError,
+    empty_scope,
+    process_prog,
+)
 
 direct_fallback_data = {"model": "raise an error", "fallback": "The error was caught"}
 
@@ -35,3 +43,48 @@ def test_error_in_sequence():
     data = Program.model_validate(error_in_sequence_data)
     text, _, _, _ = process_prog(state, empty_scope, data)
     assert text == "The error was caught"
+
+
+def test_python_exception():
+    prog_str = """
+code: "raise Exception()"
+lang: python
+fallback: "Exception caught"
+"""
+    result = exec_str(prog_str)
+    assert result == "Exception caught"
+
+
+def test_parse_regex_error():
+    prog_str = """
+text: "Hello"
+parser:
+    regex: "(e"
+fallback: "Exception caught"
+"""
+    result = exec_str(prog_str)
+    assert result == "Exception caught"
+
+
+def test_type_checking():
+    prog_str = """
+text: "Hello"
+spec: int
+fallback: 4012
+"""
+    result = exec_str(prog_str)
+    assert result == 4012
+
+
+def test_type_checking_in_fallback():
+    prog_str = """
+model: "raise an error"
+spec: int
+fallback: "Error"
+"""
+    with pytest.raises(PDLRuntimeError) as exc:
+        _ = exec_str(prog_str)
+    assert (
+        str(exc.value.message)
+        == "Type errors during spec checking:\nline 0 - Error should be of type <class 'int'>"  # TODO: check line number
+    )