Simplify Exit Exception

= Refactor BaseCommand to simplify Exit handling

BaseCommand.main() will get the return value from `self.invoke` and
pass it to `ctx.exit()`, so that commands which `return 1` will
`ctx.exit(1)`
This is not a behavioral change -- `ctx.exit()` already does this.

Do not reraise Exit exceptions when invoked non-standalone. Instead,
return their exit codes as the result of `BaseCommand.main`. So, a
command which explicitly invokes `ctx.exit(0)` in its execution will
effectively `return 0` instead of raising a specialized exception.

= Make Exit its own RuntimeError subtype, don't pollute stdio on exit

Exit exceptions should not be a subtype of ClickException with the
output pretty-printing (`show()`) which happens when they are raised in
non-standalone mode. That would make `ctx.exit(...)` needlessly pollute
stderr. This would have downstream impact on everyone using context exit
calls, and generally be a Bad Thing (tm).

Instead, like Abort, Exit is a subclass of RuntimeError with very little
"meat on its bones". It's an exception containing a single integer (exit
code)  which is then interpreted in that way in BaseCommand.main

closes #533
closes #667

1 files changed, 4 insertions, 13 deletions

diff --git a/tests/test_context.py b/tests/test_context.py
index cad2ae3..35933be 100644
--- a/tests/test_context.py
+++ b/tests/test_context.py
@@ -1,6 +1,4 @@
 # -*- coding: utf-8 -*-
-import pytest
-
 import click
 
 
@@ -195,6 +193,7 @@ def test_close_before_pop(runner):
     @click.pass_context
     def cli(ctx):
         ctx.obj = 'test'
+
         @ctx.call_on_close
         def foo():
             assert click.get_current_context().obj == 'test'
@@ -243,25 +242,17 @@ def test_make_pass_decorator_args(runner):
     assert result.output == 'foocmd\n'
 
 
-def test_exit_not_standalone_failure():
+def test_exit_not_standalone():
     @click.command()
     @click.pass_context
     def cli(ctx):
         ctx.exit(1)
 
-    with pytest.raises(click.exceptions.Exit) as e:
-        cli.main([], 'test_exit_not_standalone', standalone_mode=False)
-    assert e.value.exit_code == 1
-
+    assert cli.main([], 'test_exit_not_standalone', standalone_mode=False) == 1
 
-def test_exit_not_standalone_success():
     @click.command()
     @click.pass_context
     def cli(ctx):
         ctx.exit(0)
 
-    assert cli.main(
-        [],
-        'test_exit_not_standalone',
-        standalone_mode=False,
-    ) is None
+    assert cli.main([], 'test_exit_not_standalone', standalone_mode=False) == 0