Merge pull request #200 from reventlov/debug_stop_after_step

Add `--debug-stop-before-step` flag.

compiler/front_end/emboss_front_end.py

@@ -55,6 +55,11 @@ def _parse_command_line(argv):
         help="Show the module-level IR of the main input file "
         "before symbol resolution.",
     )
+    parser.add_argument(
+        "--debug-stop-before-step",
+        type=str,
+        help="Stop processing before the specified step.",
+    )
     parser.add_argument(
         "--debug-show-full-ir",
         action="store_true",
@@ -146,7 +151,7 @@ def _find_and_read(file_name):
     return _find_and_read
 
 
-def parse_and_log_errors(input_file, import_dirs, color_output):
+def parse_and_log_errors(input_file, import_dirs, color_output, stop_before_step=None):
     """Fully parses an .emb and logs any errors.
 
     Arguments:
@@ -158,7 +163,9 @@ def parse_and_log_errors(input_file, import_dirs, color_output):
       (ir, debug_info, errors)
     """
     ir, debug_info, errors = glue.parse_emboss_file(
-        input_file, _find_in_dirs_and_read(import_dirs)
+        input_file,
+        _find_in_dirs_and_read(import_dirs),
+        stop_before_step=stop_before_step,
     )
     if errors:
         _show_errors(errors, ir, color_output)
@@ -168,7 +175,10 @@ def parse_and_log_errors(input_file, import_dirs, color_output):
 
 def main(flags):
     ir, debug_info, errors = parse_and_log_errors(
-        flags.input_file[0], flags.import_dirs, flags.color_output
+        flags.input_file[0],
+        flags.import_dirs,
+        flags.color_output,
+        stop_before_step=flags.debug_stop_before_step,
     )
     if errors:
         return 1

compiler/front_end/glue.py

@@ -19,6 +19,7 @@
 """
 
 import collections
+import sys
 
 from compiler.front_end import attribute_checker
 from compiler.front_end import constraints
@@ -323,9 +324,11 @@ def process_ir(ir, stop_before_step):
         constraints.check_constraints,
         write_inference.set_write_methods,
     )
-    assert stop_before_step in [None] + [
-        f.__name__ for f in passes
-    ], "Bad value for stop_before_step."
+    valid_step_names = [f.__name__ for f in passes]
+    assert stop_before_step in [None] + valid_step_names, (
+        f"Bad value '{stop_before_step}' for stop_before_step.  Valid values: "
+        + " ".join(valid_step_names)
+    )
     # Some parts of the IR are synthesized from "natural" parts of the IR, before
     # the natural parts have been fully error checked.  Because of this, the
     # synthesized parts can have errors; in a couple of cases, they can have