Adding some error handling abilities

pie.py

@@ -4,7 +4,7 @@
 Enables a user to execute predefined tasks that may accept parameters and options from the command line without any other required packages.
 Great for bootstrapping a development environment, and then interacting with it.
 """
-__VERSION__='0.2.5'
+__VERSION__='0.2.6'
 
 
 import inspect
@@ -26,7 +26,7 @@
 
 # function for input (also so that we can mock it tests)
 INPUT_FN=input if PY3 else raw_input
-# function to execute a command - must emulate the subprocess call method
+# function to execute a command - must emulate the subprocess call method and return an error code on failure
 CMD_FN=subprocess.call
 
 
@@ -213,6 +213,13 @@ class CmdContextManager(object):
     """
     context=[]
 
+
+    class CmdError(Exception):
+        def __init__(self,errorcode,cmd):
+            self.errorcode=errorcode
+            self.cmd=cmd
+
+
     @classmethod
     def enter(cls,ctx):
         cls.context.append(ctx)
@@ -222,7 +229,9 @@ def enter(cls,ctx):
     def cmd(cls,c,i=None):
         if i is None: i=len(cls.context)
         if i>0: return cls.context[i-1].cmd(c)
-        return CMD_FN(c,shell=True)
+        errorcode=CMD_FN(c,shell=True)
+        if errorcode!=0:
+            raise cls.CmdError(errorcode,c)
 
     @classmethod
     def exit(cls):
@@ -520,30 +529,34 @@ def main(args):
                     # pick up the specific case of not being able to find a pie_tasks module/package
                     # handle different attributes and messages in py2 vs py3
                     if isinstance(e,ImportError) and (getattr(e,'message','')=='No module named pie_tasks' or getattr(e,'msg','')=="No module named 'pie_tasks'"):
-                        print('pie_tasks could not be found.')
+                        print('pie_tasks could not be found.',file=sys.stderr)
                     else:
-                        print('An error occurred when importing pie_tasks:\n'+traceback.format_exc())
+                        print('An error occurred when importing pie_tasks:\n'+traceback.format_exc(),file=sys.stderr)
                     return 1
 
             else:
                 # otherwise, we need to activate and run pie again, within the venv
                 if pv.exists():
                     return pv.run_pie(args)
                 else:
-                    print('{} not found. You can create it with the -R argument.'.format(pv.PIE_VENV))
+                    print('{} not found. You can create it with the -R argument.'.format(pv.PIE_VENV),file=sys.stderr)
                     return 1
 
         # try to execute each arg
         for a in parsed_args:
             try:
                 a.execute()
+            except CmdContextManager.CmdError as e:
+                print('Error when executing command "{}". Errorcode = {}'.format(e.cmd,e.errorcode),file=sys.stderr)
+                return e.errorcode
             except TaskCall.TaskNotFound as e:
-                print('Task {} could not be found.'.format(e.name))
-                break
+                print('Task {} could not be found.'.format(e.name),file=sys.stderr)
+                return 1
+        return 0
 
     else:
         Help().execute()
-
+        return 1
 
 
 if __name__=='__main__':

pie_tasks.py

@@ -3,7 +3,7 @@
 
 @task
 def setup():
-    createVenvs()
+    createVenv()
     updatePackages()
 
 

tests/data/error_handling/pie_tasks.py

@@ -0,0 +1,18 @@
+from pie import *
+
+
+@task
+def cmd_no_failure():
+    cmd('python -c "print(\'alpha\')"')
+
+
+@task
+def cmd_failure_non_existent():
+    cmd('non_existent')
+    cmd('python -c "print(\'beta\')"')
+
+
+@task
+def cmd_failure_error_code():
+    cmd('python -c "import sys; sys.exit(3)"')
+    cmd('python -c "print(\'gamma\')"')

tests/test_calling_tasks.py

@@ -3,6 +3,7 @@
 
 @pytest.mark.parametrize('pie_tasks_path',['missing_task'],indirect=['pie_tasks_path'])
 def test_missing_task(pie,capsys,pie_tasks_path):
-    pie.main(['missing'])
+    r=pie.main(['missing'])
     out,err=capsys.readouterr()
-    assert out.startswith('Task missing could not be found.')
+    assert err.startswith('Task missing could not be found.')
+    assert r==1

tests/test_error_handling.py

@@ -0,0 +1,26 @@
+import os
+
+import pytest
+
+
+@pytest.mark.parametrize('pie_tasks_path',['error_handling'],indirect=['pie_tasks_path'])
+def test_cmd_no_failure(pie,capfd,pie_tasks_path):
+    pie.main(['cmd_no_failure'])
+    out,err=capfd.readouterr()
+    out=out.replace(os.linesep,'\n')
+    assert out=='alpha\n'
+
+@pytest.mark.parametrize('pie_tasks_path',['error_handling'],indirect=['pie_tasks_path'])
+def test_cmd_failure_non_existent(pie,capfd,pie_tasks_path):
+    errorcode=pie.main(['cmd_failure_non_existent'])
+    out,err=capfd.readouterr()
+    assert not out.endswith('beta\n')
+    assert errorcode==1
+
+@pytest.mark.parametrize('pie_tasks_path',['error_handling'],indirect=['pie_tasks_path'])
+def test_cmd_failure_error_code(pie,capfd,pie_tasks_path):
+    errorcode=pie.main(['cmd_failure_error_code'])
+    out,err=capfd.readouterr()
+    assert not out.endswith('gamma\n')
+    assert errorcode==3
+

tests/test_importing_pie_tasks.py

@@ -10,16 +10,18 @@ def test_help(pie,capsys,pie_tasks_path):
 
 @pytest.mark.parametrize('pie_tasks_path',['no_pie_tasks'],indirect=['pie_tasks_path'])
 def test_list_no_pie_tasks(pie,capsys,pie_tasks_path):
-    pie.main(['-l'])
+    r=pie.main(['-l'])
     out,err=capsys.readouterr()
-    assert out.startswith('pie_tasks could not be found.')
+    assert err.startswith('pie_tasks could not be found.')
+    assert r==1
 
 
 @pytest.mark.parametrize('pie_tasks_path',['error_importing_pie_tasks'],indirect=['pie_tasks_path'])
 def test_list_error_importing_pie_tasks(pie,capsys,pie_tasks_path):
-    pie.main(['-l'])
+    r=pie.main(['-l'])
     out,err=capsys.readouterr()
-    assert out.startswith('An error occurred when importing pie_tasks:')
+    assert err.startswith('An error occurred when importing pie_tasks:')
+    assert r==1
 
 
 @pytest.mark.parametrize('pie_tasks_path',['package_tasks','module_tasks'],indirect=['pie_tasks_path'])

tests/test_pie_requirements.py

@@ -3,9 +3,10 @@
 
 @pytest.mark.parametrize('pie_tasks_path',['pie_requirements'],indirect=['pie_tasks_path'])
 def test_no_venv(pie,capsys,pie_tasks_path):
-    pie.main(['test'])
+    r=pie.main(['test'])
     out,err=capsys.readouterr()
-    assert out.startswith('.venv-pie not found. You can create it with the -R argument.')
+    assert err.startswith('.venv-pie not found. You can create it with the -R argument.')
+    assert r==1
 
 
 @pytest.mark.parametrize('pie_tasks_path',['pie_requirements'],indirect=['pie_tasks_path'])