docs(v3): add v3 preview docs

Author: mcous

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2020-2023, Michael Cousins
+Copyright (c) 2020-2026, Michael Cousins
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

codebook.toml

@@ -0,0 +1,8 @@
+words = [
+    "matcher's",
+    "matchers",
+    "mock's",
+    "mundo",
+    "stubbings",
+    "verden",
+]

decoy/errors.py

@@ -12,12 +12,7 @@
 
 
 class MockNameRequiredError(ValueError):
-    """An error raised if a name is not provided for a mock.
-
-    See the [MockNameRequiredError guide][] for more details.
-
-    [MockNameRequiredError guide]: usage/errors-and-warnings.md#mocknamerequirederror
-    """
+    """A name was not provided for a mock."""
 
     @classmethod
     def create(cls) -> "MockNameRequiredError":
@@ -26,20 +21,16 @@ def create(cls) -> "MockNameRequiredError":
 
 
 class MockSpecInvalidError(TypeError):
-    """An value passed as a mock spec is not valid."""
+    """A value passed as a mock spec is not valid."""
 
 
 class MissingRehearsalError(ValueError):
-    """An error raised when a Decoy method is called without rehearsal(s).
+    """A Decoy method was called without rehearsal(s).
 
     This error is raised if you use [`when`][decoy.Decoy.when],
     [`verify`][decoy.Decoy.verify], or [`prop`][decoy.Decoy.prop] incorrectly
     in your tests. When using async/await, this error can be triggered if you
     forget to include `await` with your rehearsal.
-
-    See the [MissingRehearsalError guide][] for more details.
-
-    [MissingRehearsalError guide]: usage/errors-and-warnings.md#missingrehearsalerror
     """
 
     @classmethod
@@ -57,13 +48,10 @@ class ThenDoActionNotCallableError(TypeError):
 
 
 class MockNotAsyncError(TypeError):
-    """An error raised when an asynchronous function is used with a synchronous mock.
+    """An asynchronous function was passed to a synchronous mock.
 
     This error is raised if you pass an `async def` function
-    to a synchronous stub's `then_do` method.
-    See the [MockNotAsyncError guide][] for more details.
-
-    [MockNotAsyncError guide]: usage/errors-and-warnings.md#mocknotasyncerror
+    to a synchronous stub's [`then_do`][decoy.Stub.then_do] method.
     """
 
 
@@ -72,17 +60,7 @@ class SignatureMismatchError(TypeError):
 
 
 class VerifyError(AssertionError):
-    """An error raised when actual calls do not match rehearsals given to `verify`.
-
-    See [spying with verify][] for more details.
-
-    [spying with verify]: usage/verify.md
-
-    Attributes:
-        rehearsals: Rehearsals that were being verified.
-        calls: Actual calls to the mock(s).
-        times: The expected number of calls to the mock, if any.
-    """
+    """A [`Decoy.verify`][decoy.Decoy.verify] assertion failed."""
 
     rehearsals: Sequence[VerifyRehearsal]
     calls: Sequence[SpyEvent]
@@ -119,9 +97,4 @@ def create(
 
 
 class VerifyOrderError(VerifyError):
-    """An error raised when the order of calls do not match expectations.
-
-    See [spying with verify][] for more details.
-
-    [spying with verify]: usage/verify.md
-    """
+    """A [`Decoy.verify_order`][decoy.next.Decoy.verify_order] assertion failed."""

docs/usage/matchers.md

@@ -51,7 +51,7 @@ When testing certain APIs, especially callback APIs, it can be helpful to captur
 
 For example, our test subject may register an event listener handler, and we want to test our subject's behavior when the event listener is triggered.
 
-```py
+```python
 import pytest
 from typing import cast, Optional
 from decoy import Decoy, matchers

docs/usage/verify.md

@@ -69,8 +69,8 @@ say_hello = decoy.mock(name="say_hello")
 
 say_hello("foobar")
 
-decoy.verify(matchers.StringMatching("^foo"), times=1)  # passes
-decoy.verify(matchers.StringMatching("^bar"), times=1)  # raises
+decoy.verify(say_hello(matchers.StringMatching("^foo")), times=1)  # passes
+decoy.verify(say_hello(matchers.StringMatching("^bar")), times=1)  # raises
 ```
 
 ## Verifying with async/await

docs/v3/about.md

@@ -0,0 +1,54 @@
+# Decoy v3 Preview
+
+The next major version of Decoy is a ground-up rebuild of the library. In the years since Decoy was first written, the Python typing system has advanced, especially when it comes to typing functions. These advancements, especially the addition of [`ParamSpec`][paramspec], unblocked a much simpler API (as well as internal implementation) for Decoy.
+
+In order to ease the migration to the new API, the v3 API has been added as a preview to the v2 release (starting with `v2.4.0`) as `decoy.next`.
+
+```diff
+- from decoy import Decoy
++ from decoy.next import Decoy
+```
+
+!!! warning
+
+    `decoy.next` is a **preview** and not subject to semver.
+    No major changes are anticipated, but cannot be guaranteed until
+    Decoy v3 is released.
+
+## Setup
+
+In order to use the v3 preview, you must be using:
+
+- `decoy >= 2.4.0`
+- `python >= 3.10`
+
+Then, start trying out the new API!
+
+```diff
+- from decoy import Decoy
++ from decoy.next import Decoy
+
+
++ @pytest.fixture()
++ def decoy() -> collections.abc.Iterator[Decoy]:
++     """Create a Decoy v3 preview instance for testing."""
++     with Decoy.create() as decoy:
++         yield decoy
+
+
+  def test_when(decoy: Decoy) -> None:
+      mock = decoy.mock(cls=SomeClass)
+-     decoy.when(mock.foo("hello")).then_return("world")
++     decoy.when(mock.foo).called_with("hello").then_return("world")
+
+
+   def test_verify(decoy: Decoy) -> None:
+      mock = decoy.mock(cls=SomeClass)
+      mock.foo("hello")
+-     decoy.verify(mock.foo("hello"))
++     decoy.verify(mock.foo).called_with("hello")
+```
+
+See the [migration guide](./migration.md) for more details.
+
+[paramspec]: https://docs.python.org/3/library/typing.html#typing.ParamSpec

docs/v3/api.md

@@ -0,0 +1,9 @@
+# API Reference
+
+!!! warning
+
+    `decoy.next` is a **preview** and not subject to semver.
+    No major changes are anticipated, but cannot be guaranteed until
+    Decoy v3 is released.
+
+::: decoy.next

docs/v3/attributes.md

@@ -0,0 +1,122 @@
+# Mock attributes
+
+Python [property attributes][] provide an interface for creating read-only properties and properties with getters, setters, and deleters. You can use Decoy to stub these properties.
+
+[property attributes]: https://docs.python.org/3/library/functions.html#property
+
+## Default behavior
+
+Unlike mock method calls - which have a default return value of `None` - Decoy's default return value for attribute access is **another mock**. You don't need to configure anything explicitly if you need a `@property` getter to return another mock; Decoy will inspect type annotations and configure the proper child mock for you.
+
+```python
+class Child:
+    ...
+
+class Parent:
+    @property
+    def child(self) -> Child:
+        ...
+
+mock_parent = decoy.mock(cls=Parent)
+
+assert isinstance(mock_parent, Dependency)
+assert isinstance(mock_parent.child, Child)
+```
+
+You may also manually set any mock attribute to "opt out" of Decoy for a given attribute. To opt back into Decoy, delete the attribute.
+
+```python
+dep = decoy.mock(cls=Parent)
+
+dep.child = "don't worry about it"
+assert dep.child == "don't worry about it"
+
+del dep.child
+assert isinstance(mock_parent.child, Child)
+```
+
+## Stub attribute access
+
+### Stub a getter
+
+Use [`When.get`][decoy.next.When.get] stub a return value for an attribute instead of returning a child mock.
+
+```python
+dependency = decoy.mock(name="dependency")
+
+decoy.when(dependency.some_property).get().then_return(42)
+
+assert dep.some_property == 42
+```
+
+You can also configure any other behavior, like raising an error.
+
+```python
+dependency = decoy.mock(name="dependency")
+
+decoy
+    .when(dependency.some_property)
+    .get()
+    .then_raise(RuntimeError("oh no"))
+
+with pytest.raises(RuntimeError, match="oh no"):
+    dependency.some_property
+```
+
+### Stub a setter or deleter
+
+While you cannot stub a return value for a getter or setter, because set and delete expressions do not return a value in Python, you _can_ stub a `raise` or a side effect with [`When.set`][decoy.next.When.set] and [`When.delete`][decoy.next.When.delete].
+
+```python
+dependency = decoy.mock(name="dependency")
+
+decoy
+    .when(dependency.some_property)
+    .set(42)
+    .then_raise(RuntimeError("oh no"))
+
+decoy
+    .when(dependency.some_property)
+    .delete()
+    .then_raise(RuntimeError("what a disaster"))
+
+with pytest.raises(RuntimeError, match="oh no"):
+    dependency.some_property = 42
+
+with pytest.raises(RuntimeError, match="what a disaster"):
+    del dependency.some_property
+```
+
+## Verify property access
+
+You can verify calls to property setters and deleters with [`Verify.set`][decoy.next.Verify.set] and [`Verify.delete`][decoy.next.Verify.delete].
+
+!!! tip
+
+    Use this feature sparingly! If you're designing a dependency that triggers a side-effect, consider using a regular method, instead.
+
+    Mocking and verifying property setters and deleters is most useful for testing code that needs to interact with older or legacy dependencies that would be prohibitively expensive to redesign.
+
+### Verify a setter
+
+Use [`Verify.set`][decoy.next.Verify.set] to check that an attribute was set.
+
+```python
+dependency = decoy.mock(name="dependency")
+
+dependency.some_property = 42
+
+decoy.verify(dependency.some_property).set(42)
+```
+
+### Verify a deleter
+
+Use [`Verify.delete`][decoy.next.Verify.delete] to check that an attribute was deleted.
+
+```python
+dependency = decoy.mock(name="dependency")
+
+del dependency.some_property
+
+decoy.verify(dependency.some_property).delete)
+```

docs/v3/context-managers.md

@@ -0,0 +1,76 @@
+# Mock context managers
+
+In Python, `with` statement [context managers][] provide an interface to execute code inside a given "runtime context." This context can define consistent, failsafe setup and teardown behavior. For example, Python's built-in file objects provide a context manager interface to ensure the underlying file resource is opened and closed cleanly, without the caller having to explicitly deal with it:
+
+```python
+with open("hello-world.txt", "r") as f:
+    contents = f.read()
+```
+
+You can use Decoy to mock out your dependencies that provide a context manager interface.
+
+[context managers]: https://docs.python.org/3/reference/datamodel.html#context-managers
+
+## Generator-based context managers
+
+Using the [contextlib][] module, you can [decorate a generator function][] or method to turn its yielded value into a context manager. To mock a generator function context manager, use [`Stub.then_enter_with`][decoy.next.Stub.then_enter_with].
+
+```python
+@contextlib.contextmanager
+def open_config(path: str) -> collections.abc.Iterator[bool]:
+    ...
+
+
+def test_generator_context_manager(decoy: Decoy) -> None:
+    mock_open_config = decoy.mock(func=open_config)
+
+    decoy
+        .when(mock_open_config)
+        .called_with("some_flag")
+        .then_enter_with(True)
+
+    with mock_open_config("some_flag") as result:
+        assert result is True
+```
+
+[contextlib]: https://docs.python.org/3/library/contextlib.html
+[decorate a generator function]: https://docs.python.org/3/library/contextlib.html#contextlib.contextmanager
+
+## Class-based context managers
+
+You can stub out a context manager's `__enter__` and `__exit__` method like any other method.
+
+```python
+def test_context_manager(decoy: Decoy) -> None:
+    subject = decoy.mock(name="cm")
+
+    decoy.when(subject.__enter__).called_with().then_return("hello world")
+
+    with subject as result:
+        assert result == "hello world"
+
+    decoy.verify(subject.__exit__).called_with(None, None, None)
+```
+
+This also works with asynchronous `__aenter__` and `__aexit__`
+
+## Context manager state
+
+You can also configure stubs and verifications to only match calls made while a context manager mock is entered using the `is_entered` option to `called_with`.
+
+| `is_entered` | Matching behavior                                           |
+| ------------ | ----------------------------------------------------------- |
+| `True`       | Only matches calls made between `__enter__` and `__exit__`  |
+| `False`      | Only matches calls made if context manager is _not_ entered |
+| `None`       | Match the call regardless of context manager entry state    |
+
+```python
+decoy
+    .when(subject.read, is_entered=True)
+    .called_with("some_flag")
+    .then_return(True)
+
+decoy
+    .verify(subject.write, is_entered=True)
+    .called_with("some_flag", "new_value")
+```