Returns

Features

- Enables Pattern Matching support for `Result` containers
- Enables Pattern Matching support for `Maybe` container
- Enables Pattern Matching support for `IOResult` container
- Improves `hypothesis` plugin, now we detect
when type cannot be constructed and give a clear error message
- Adds the option to pass what exceptions `safe` will handle

Features

- Makes `_Nothing` a singleton
- Refactor `flow` function to be faster

Bugfixes

- Fixes that `assert_trace` was not catching containers
from `safe`-wrapped functions

Misc

- Fixes typos in documentation

Features

- Adds Higher Kinded Types partial support

- **Breaking**: drops `python3.6` support
- **Breaking**: makes our `mypy` plugin not optional, but required!
- **Breaking**: changes all `RequiresContext`-based type arguments order,
previously we used to specify `_EnvType` as the first type argument,
now it is the last one. This is done to respect new HKT rules
- **Breaking**: renames `.rescue` to `.lash`
- **Breaking**: removes all old interfaces from `primitives/interfaces.py`,
use new typeclasses instead
- **Breaking**: ``Maybe`` is fully reworked to be lawful
- **Breaking**: removes `value_or` pointfree method,
because it is impossible to express with HKT
- **Breaking**: removes `.value_or`, `.unwrap`, and `.failure` methods
from `FutureResult` and `RequiresContext`-based types,
because we do require these methods to raise an exception on failure,
but these methods were lazy and did not raise the required exception
- **Breaking**: changes how `is_successful` is typed:
now we allow any `Unwrappable` interface instances there,
including custom ones
- **Breaking**: changes `UnwrapFailedError` constructor,
now it does accept an `Unwrappable` instance instead of a `BaseContainer`
- **Breaking**: removes `.fix` method from all containers,
also removes `fix` pointfree function
- **Breaking**: Removes `coalesce` function,
because it is impossible to properly type it
- **Breaking**: Removes all `Context*` based types with `.ask()` method,
use new `.ask()` methods on the `Reader`-based containers
- **Breaking**: Now `Future` and `FutureResult` can be awaited multiple times
- **Breaking**: Removes `.unify()` method from several containers,
use `unify()` pointfree function instead
- **Breaking**: Removes ``.from_iterable`` method from all containers,
instead adds better `iterables` support,
we now have `returns.iterables` module with `Fold` helper
- **Breaking**: Renames property `empty` to `no_args` of
all `RequiresContext`-based classes

- Adds new public interfaces: see `returns.interfaces`
- Adds `methods` package with several helpful things inside

- Adds `FutureSuccess` and `FutureFailure` unit functions
to be similar to `Result` and `IOResult`
- Adds `.swap` method to `Result`, `IOResult`, `FutureResult`,
and other result based containers
- Adds `.modify_env` method to all `RequiresContext*` types
- Adds `.rescue` to `Maybe`
- Adds `.equals` methods to types that can be compared directly:
`Result`, `Maybe`, `IO`, `IOResult`
- Adds missing `from_requires_context_future_result` to `RequiresContext`
- Adds `.from_optional` and `.bind_optional` to `Maybe` container
- Adds `__slots__` to `UnwrapFailedError` with `halted_container`
- Changes `flatten` to work with `KindN` and any possible container
- Adds a helper to test traces to our `pytest` plugin
- Adds `cond` function to `pointfree` and `methods` packages
- Adds `compose_result` HKT method and pointfree function
- Adds `unify` HKT pointfree function
- Adds `bimap` pointfree function
- Adds `unwrap_or_failure` function to `methods` package

- Adds `collect_trace` helper function for better development experience
- Adds `hypothesis` integration and pre-defined "monad laws as values"

- Adds `assert_equal` method to our `pytest` plugin

Bugfixes

- **Breaking**: fixes serious typing issue and changes how `flow` works
- **Breaking**: fixes serious typing issue and changes how `pipe` works,
now it has a hard limit of 20 parameters
- Fixes that `RequiresContextFutureResult` was not supported by `pytest` plugin
- Fixes incorrect `partial` behaviour in an edge case, 618
- Fixes that `.apply` method of `IOResult` was working incorrectly,
it was returning `IOFailure(2)`
as a result of `IOFailure(1).apply(IOFailure(2))`
- Fixes bug that `safe(tap(...))` was revealing invalid types sometimes

Misc

- Adds a lot of new typetests
- Checks that now all math laws are checked for all types
- Changes docs structure, adds new `Interfaces`, `HKT`, and `Methods` pages
- Changed `__str__` method in `BaseContainer` class to `__repr__` method
- Adds `Quickstart` guide

Features

- **Breaking**: renames mypy plugin from `decorator_plugin` to `returns_plugin`
because of a complete rewrite and lots of new features
- **Breaking**: changes `safe`, `impure`, `impure_safe`, `maybe` semantics:
they do not work with `async` functions anymore;
now you are forced to use `Future` and its helpers
to work with `async` functions
- **Breaking**: renames `Maybe.new` to `Maybe.from_value`.
Because all our other containers support this protocol.
Only `Maybe` was different, sorry for that!
- **Breaking**: renames `.from_success()` to `.from_value()`,
there's no need in two separate methods
- **Breaking**: renames `.from_successful_io()` to `.from_io()`,
there's no need in two separate methods
- **Breaking**: renames `.from_successful_context()` to `.from_context()`,
there's no need in two separate methods
- **Breaking**: since we now support `.apply()` method,
there's no more need in `*_squash` converters, they are removed
- **Breaking**: renamed `Instanceable` to `Applicative`
- **Breaking**: changes `.from_io` and `.from_failed_io` of `IOResult`
to return `Any` instead of `NoReturn` unfilled type
- **Breaking**: removes `.lift` and `.lift_*` methods from all containers,
use `map_`, `bind_result`, `bind_io`, and other pointfree helpers instead
- **Breaking**: removes `pipeline` function. It was a mistake:
it does not work with mixed container types,
it does not type failures properly,
it does not work with ``IO`` and ``Future``,
it enforces to write imperative code in a functional codebase.
Use ``flow`` instead

- Adds typed `partial` and `curry` mypy plugins!
- Adds typed `flow` plugin, now it can accept any number of arguments,
it now also has **excellent** type inference
- Adds typed `pipe` plugin, now it can accept any number of arguments,
it now also has good type inference
- Adds `managed` pipeline function that is useful
for working with stateful computations

- Adds typed `map_`, `fix`, and `alt` pointfree functions
- Adds typed `bind_result`, `bind_io`, `bind_ioresult`,
`bind_context`, `bind_context_result`, `bind_future`,
`bind_async`, and `bind_awaitable` pointfree functions
- Adds typed `bind_async_future` and `bind_async_future_result`
pointfree functions
- Adds typed `unify` pointfree function
- Adds typed `apply` pointfree function
- Adds typed `value_or` pointfree function

- Adds `pytest` plugin with the ability to tests error handling

- Adds `Future` container to easily work with `async` functions
- Adds `FutureResult` container to easily work
with `async` function that might fail
- Adds `RequiresContextFutureResult` container
- Adds `ReaderFutureResult` alias for `RequiresContextFutureResult`
- Adds `RequiresContextFutureResultE` and `ReaderFutureResultE` aliases
- Adds `Future`, `FutureResult` and `RequiresContextFutureResult`
support for all existing pointfree functions

- Adds `bind_io` method to `IOResult`
- Adds `bind_io` method to `RequiresContextIOResult`
- Adds `or_else` method to `Maybe`
- Adds `.from_io` and `.from_failed_io` to `RequiresContextIOResult`

- Syncs naming in `from_*` methods, now all parameters are named `inner_value`
- Adds `not_` composition helper
- Adds `flatten` support for `Future`,
`FutureResult` and `RequiresContextFutureResult`
- Adds `__copy__` and `__deepcopy__` magic methods to `Immutable` class
- Speeds up ``is_successful`` function
- Makes all `Context` context helpers abstract,
so you cannot create new instances of this class,
also adds `__slots__` to these classes
- Improves `RequiresContext*` types with `NoDeps` where it is logically true

Bugfixes

- Fixes that `safe` decorator was generating incorrect signatures
for functions with `Any`
- Fixes that `.rescue()` of `RequiresContextResult` was returning `Any`
- Fixes that `.rescue()` of `RequiresContextIOResult` was returning `Any`
- Fixes that `RequiresContextResult` and `RequiresContextIOResult`
were not `final`
- Fixes that `ImmutableStateError` was not a subclass of `AttributeError`
- Fixes that `IOResult` was not showing `str` representation
of wrapped `inner_value`

Misc

- Replaces `pytest-asyncio` with `anyio` plugin,
now we test compatibility with any IO stack: `asyncio`, `trio`, `curio`
- Updates lots of dependencies
- Adds lots of new tests
- Updates lots of docs
- Removes "IO marker" name from docs in favor for "IO container",
it is not special at all. Why would we call it differently?

Features

- **Breaking**: renames `join` to `flatten`, sorry!
- **Breaking**: renames `box` to `bind` and moves it to `returns.pointfree`
- **Breaking**: removes `Maybe.rescue` and `Maybe.fix` methods
- **Breaking**: renames `io_squash` to `squash_io`
and moves it to `returns.converters`
- **Breaking**: moves all interfaces from `returns.primitives.container` to
`returns.primitives.interfaces`

- Adds `rescue` pointfree function
- Adds `ResultE` alias for `Result[..., Exception]`

- Adds `RequiresContext` container and `Context` helper class
- Adds `RequiresContext` support for `bind` pointfree function
- Adds `RequiresContext` support for `flatten` function

- Adds `RequiresContextResult` container
- Adds `RequiresContextResultE` alias
- Adds `ReaderResult` and `ReaderResultE` aliases
for `RequiresContextResult[..., ..., Exception]`
- Adds `RequiresContextResult` support for `bind` and `rescue`
- Adds `RequiresContextResult` support for `flatten`

- Adds `IOResult` helper to work better with `IO[Result[a, b]]`
- Adds `IOResultE` alias for `IOResult[a, Exception]`
- Adds `IOResult` support for `bind`
- Adds `IOResult` support for `flatten`
- Adds `IOResult` support for `pipeline`
- Adds `IOResult` support for `coalesce`
- Adds `IOResult` support for `is_successful`

- Adds `RequiresContextIOResult` container
- Adds `RequiresContextIOResultE` alias
- Adds `ReaderIOResult` and `ReaderIOResultE` aliases
for `RequiresContextIOResult[..., ..., Exception]`
- Adds `RequiresContextIOResult` support for `bind` and `rescue`
- Adds `RequiresContextIOResult` support for `flatten`

- Adds `Result.lift`, `Maybe.lift`, `RequiresContext.lift`,
and `RequiresContextResult.lift` functions in addition to `IO.lift`

- Adds `Immutable` primitive type
- Adds `Unitable` protocol and `.from_success()` and `.from_failure()`
methods for all `Result` related classes
- Adds `Instanceable` protocol and `.from_value()` method
for `IO` and `RequiresContext`

- Adds `flow` function, which is similar to `pipe`
- Adds `swap` converter for `Result` and `IOResult`
- Adds `squash_context` function to squash `RequiresContext` similar to `IO`

Bugfixes

- Now `Success` and `Failure` (both `io` and pure) return `Any` and not `NoReturn`
- Fixes how `flatten` works, also adds more tests and docs about `Failure` case
- Fixes `Unwrappable` type being parametrized with only one `TypeVar`
- Changes `Success` and `Failure` to return `Any` instead of `NoReturn`

Misc

- Updates `poetry` version in `travis`
- Improves ``pipe`` docs with ``lambda`` and `Generic` problem
- Improves docs in several places
- Now examples in docs tries to be docstests where possible
- Changes how tests are checked with `mypy` in CI

Features

- **Breaking**: now `pipeline` requires a container type when created:
`pipeline(Result)` or `pipeline(Maybe)`
- `Maybe` and `Result` now has `success_type` and `failure_type` aliases
- Adds `Result.unify` utility method for better error type composition
- We now support `dry-python/classes` as a first-class citizen
- Adds `io_squash` to squash several `IO` containers into one container
with a tuple inside, currently works with `9` containers max at a time
- Adds `untap` function which does convert return type to `None`

Bugfixes

- Fixes that containers were not usable with `multiprocessing`
- Changes the inheritance order, now `BaseContainer` is the first child
- Fixes that `Nothing` had incorrect docstrings

Misc

- Now `generated` package is protected
- Updates `poetry` to `1.0`