feat: Show exceptions if they happened during loading a WSGI application

docs/changelog.rst

@@ -6,9 +6,18 @@ Changelog
 `Unreleased`_
 -------------
 
+Added
+~~~~~
+
+- Show exceptions if they happened during loading a WSGI application. Option ``--show-errors-tracebacks`` will display a
+  full traceback.
+
 `1.3.1`_ - 2020-04-27
 ---------------------
 
+Fixed
+~~~~~
+
 - Packaging issue
 
 `1.3.0`_ - 2020-04-27

src/schemathesis/cli/__init__.py

@@ -144,7 +144,13 @@ def schemathesis(pre_run: Optional[str] = None) -> None:
 )
 @click.option("--validate-schema", help="Enable or disable validation of input schema.", type=bool, default=True)
 @click.option("--junit-xml", help="Create junit-xml style report file at given path.", type=click.File("w"))
-@click.option("--show-errors-tracebacks", help="Show full tracebacks for internal errors.", is_flag=True, default=False)
+@click.option(
+    "--show-errors-tracebacks",
+    help="Show full tracebacks for internal errors.",
+    is_flag=True,
+    is_eager=True,
+    default=False,
+)
 @click.option("--store-network-log", help="Store requests and responses into a file", type=click.File("w"))
 @click.option(
     "--hypothesis-deadline",

src/schemathesis/cli/callbacks.py

@@ -44,12 +44,16 @@ def validate_app(ctx: click.core.Context, param: click.core.Parameter, raw_value
         # Since most of app instances are not-transferable to another process, they are passed as strings and
         # imported in a subprocess
         return raw_value
-    except (ImportError, ValueError, AttributeError):
-        raise click.BadParameter("Can not import application from the given module")
     except Exception as exc:
-        message = utils.format_exception(exc)
-        click.secho(f"Error: {message}", fg="red")
-        raise click.Abort
+        show_errors_tracebacks = ctx.params["show_errors_tracebacks"]
+        message = utils.format_exception(exc, show_errors_tracebacks)
+        click.secho(f"{message}\nCan not import application from the given module", fg="red")
+        if not show_errors_tracebacks:
+            click.secho(
+                "Add this option to your command line parameters to see full tracebacks: --show-errors-tracebacks",
+                fg="red",
+            )
+        raise click.exceptions.Exit(1)
 
 
 def validate_auth(

test/cli/test_callbacks.py

@@ -34,8 +34,8 @@ def test_validate_auth(value):
 
 @given(value=st.text())
 def test_validate_app(value):
-    with pytest.raises(click.BadParameter):
-        callbacks.validate_app(None, None, value)
+    with pytest.raises(click.exceptions.Exit):
+        callbacks.validate_app(SimpleNamespace(params={"show_errors_tracebacks": False}), None, value)
 
 
 @given(value=st.lists(st.text(), min_size=1).map(tuple))

test/cli/test_commands.py

@@ -951,9 +951,10 @@ def test_wsgi_app_exception(testdir, cli):
         1 / 0
         """
     )
-    result = cli.run("/swagger.yaml", "--app", f"{module.purebasename}:app")
+    result = cli.run("/swagger.yaml", "--app", f"{module.purebasename}:app", "--show-errors-tracebacks")
     assert result.exit_code == ExitCode.TESTS_FAILED
-    assert result.stdout == "Error: ZeroDivisionError: division by zero\n\nAborted!\n"
+    assert "Traceback (most recent call last):" in result.stdout
+    assert "ZeroDivisionError: division by zero" in result.stdout
 
 
 def test_wsgi_app_missing(testdir, cli):
@@ -963,11 +964,10 @@ def test_wsgi_app_missing(testdir, cli):
         """
     )
     result = cli.run("/swagger.yaml", "--app", f"{module.purebasename}:app")
-    assert result.exit_code == ExitCode.INTERRUPTED
-    assert (
-        result.stdout.strip().split("\n")[-1]
-        == "Error: Invalid value for '--app': Can not import application from the given module"
-    )
+    assert result.exit_code == ExitCode.TESTS_FAILED
+    lines = result.stdout.strip().split("\n")
+    assert "AttributeError: module 'location' has no attribute 'app'" in lines
+    assert "Can not import application from the given module" in lines
 
 
 def test_wsgi_app_internal_exception(testdir, cli, caplog):