Report error information if GDB/LLDB is not found

pystack.py

@@ -10,6 +10,7 @@
 import functools
 import codecs
 import locale
+import distutils.spawn
 
 import click
 
@@ -45,7 +46,7 @@ def make_gdb_args(pid, command):
         r'call (void) PyRun_SimpleString("exec(r\"\"\"%s\"\"\")")' % command,
         r'call (void) PyGILState_Release((void *) $1)',
     ]
-    arguments = ['gdb', '-p', str(pid), '-batch']
+    arguments = [find_debugger('gdb'), '-p', str(pid), '-batch']
     arguments.extend("-eval-command=%s" % s for s in statements)
     return arguments
 
@@ -56,11 +57,23 @@ def make_lldb_args(pid, command):
         r'expr (void) PyRun_SimpleString("exec(r\"\"\"%s\"\"\")")' % command,
         r'expr (void) PyGILState_Release($gil)',
     ]
-    arguments = ['lldb', '-p', str(pid), '--batch']
+    arguments = [find_debugger('lldb'), '-p', str(pid), '--batch']
     arguments.extend('--one-line=%s' % s for s in statements)
     return arguments
 
 
+def find_debugger(name):
+    debugger = distutils.spawn.find_executable(name)
+    if not debugger:
+        raise DebuggerNotFound(
+            'Could not find "%s" in your PATH environment variable' % name)
+    return debugger
+
+
+class DebuggerNotFound(Exception):
+    pass
+
+
 def print_stack(pid, include_greenlet=False, debugger=None, verbose=False):
     """Executes a file in a running Python process."""
     # TextIOWrapper of Python 3 is so strange.
@@ -120,7 +133,11 @@ def cli_main(pid, include_greenlet, debugger, verbose):
 
     $ pystack <pid>
     '''
-    return print_stack(pid, include_greenlet, debugger, verbose)
+    try:
+        print_stack(pid, include_greenlet, debugger, verbose)
+    except DebuggerNotFound as e:
+        click.echo('DebuggerNotFound: %s' % e.args[0], err=True)
+        click.get_current_context().exit(1)
 
 
 def tolerate_missing_locale():

test_pystack.py

@@ -5,11 +5,12 @@
 import platform
 import time
 
-from pytest import fixture, mark, param
+from pytest import fixture, mark, param, raises
 from distutils.spawn import find_executable
 from click.testing import CliRunner
 
-from pystack import cli_main, tolerate_missing_locale
+from pystack import (
+    cli_main, tolerate_missing_locale, find_debugger, DebuggerNotFound)
 
 
 skipif_non_gdb = mark.skipif(
@@ -43,6 +44,15 @@ def cli():
     return CliRunner()
 
 
+def test_find_debugger():
+    assert find_debugger('sh') == '/bin/sh'
+    with raises(DebuggerNotFound) as error:
+        find_debugger('shhhhhhhhhhhhhhhhhhhhhhhhh')
+    assert error.value.args[0] == (
+        'Could not find "shhhhhhhhhhhhhhhhhhhhhhhhh" in your'
+        ' PATH environment variable')
+
+
 @mark.parametrize(('process', 'debugger'), [
     param(STATEMENTS['sleep'], 'gdb', marks=[skipif_non_gdb, skipif_darwin]),
     param(STATEMENTS['sleep'], 'lldb', marks=skipif_non_lldb),
@@ -52,3 +62,11 @@ def test_smoke(cli, process, debugger):
     assert not result.exception
     assert result.exit_code == 0
     assert '  File "<string>", line 1, in <module>\n' in result.output
+
+
+@mark.parametrize('process', [STATEMENTS['sleep']], indirect=['process'])
+def test_smoke_debugger_not_found(cli, mocker, process):
+    mocker.patch('pystack.find_debugger', side_effect=DebuggerNotFound('oops'))
+    result = cli.invoke(cli_main, [str(process.pid)])
+    assert result.exit_code == 1
+    assert 'DebuggerNotFound: oops' in result.output

tox.ini

@@ -7,5 +7,6 @@ deps =
     pytest
     pytest-cov
     pytest-pep8
+    pytest-mock
 commands =
     py.test --cov=pystack {posargs}