Display retype errors (#52)

* Display retype errors

Catch retype failures and print the error so the user has a better
idea of what went wrong.

* Update changelog

CHANGES.rst

@@ -4,6 +4,8 @@ Changelog
 master
 ------
 
+* Display retype errors when stub application fails. Merge of #42, fixes #49.
+
 * Add ``monkeytype run -m`` for running a module as a script. Merge of
   #41. Thanks Simon Gomizelj.
 

monkeytype/cli.py

@@ -101,6 +101,10 @@ def get_stub(args: argparse.Namespace, stdout: IO, stderr: IO) -> Optional[Stub]
     return stubs.get(module, None)
 
 
+class HandlerError(Exception):
+    pass
+
+
 def apply_stub_handler(args: argparse.Namespace, stdout: IO, stderr: IO) -> None:
     stub = get_stub(args, stdout, stderr)
     if stub is None:
@@ -121,7 +125,10 @@ def apply_stub_handler(args: argparse.Namespace, stdout: IO, stderr: IO) -> None
             '--target-dir ' + src_dir,
             src_path
         ])
-        subprocess.run(cmd, shell=True, check=True, stderr=subprocess.PIPE, stdout=subprocess.PIPE)
+        try:
+            subprocess.run(cmd, shell=True, check=True, stderr=subprocess.STDOUT, stdout=subprocess.PIPE)
+        except subprocess.CalledProcessError as cpe:
+            raise HandlerError(f"Failed applying stub with retype:\n{cpe.stdout.decode('utf-8')}")
 
 
 def print_stub_handler(args: argparse.Namespace, stdout: IO, stderr: IO) -> None:
@@ -274,7 +281,11 @@ def main(argv: List[str], stdout: IO, stderr: IO) -> int:
         return 1
 
     with args.config.cli_context(args.command):
-        handler(args, stdout, stderr)
+        try:
+            handler(args, stdout, stderr)
+        except HandlerError as err:
+            print(f"ERROR: {err}", file=stderr)
+            return 1
 
     return 0
 

tests/test_cli.py

@@ -8,6 +8,7 @@
 import os
 import pytest
 import sqlite3
+import subprocess
 import tempfile
 from typing import Iterator
 
@@ -117,6 +118,24 @@ def test_display_sample_count_from_cli(store_data, stdout, stderr):
     assert ret == 0
 
 
+def test_retype_failure(store_data, stdout, stderr):
+    store, db_file = store_data
+    traces = [
+        CallTrace(func, {'a': int, 'b': str}, NoneType),
+        CallTrace(func2, {'a': int, 'b': int}, NoneType),
+    ]
+    store.add(traces)
+    msg = "this is a test"
+    err = subprocess.CalledProcessError(returncode=100, cmd='retype')
+    err.stdout = msg.encode()
+    with mock.patch.dict(os.environ, {DefaultConfig.DB_PATH_VAR: db_file.name}):
+        with mock.patch('subprocess.run', side_effect=err):
+            ret = cli.main(['apply', func.__module__], stdout, stderr)
+    assert stdout.getvalue() == ""
+    assert stderr.getvalue() == f"ERROR: Failed applying stub with retype:\n{msg}\n"
+    assert ret == 1
+
+
 def test_cli_context_manager_activated(capsys, stdout, stderr):
     ret = cli.main(['-c', f'{__name__}:LoudContextConfig()', 'stub', 'some.module'], stdout, stderr)
     out, err = capsys.readouterr()