From: Ɓukasz Langa Date: Wed, 4 Mar 2020 21:26:45 +0000 (+0100) Subject: Introduce a section of docs about exceptions X-Git-Url: https://git.madduck.net/etc/vim.git/commitdiff_plain/e253f1260d234ff925cbdbb77c140da8aa81190b Introduce a section of docs about exceptions --- diff --git a/README.md b/README.md index 45cd8f6..83429d7 100644 --- a/README.md +++ b/README.md @@ -31,11 +31,11 @@ Try it out now using the [Black Playground](https://black.now.sh). Watch the --- _Contents:_ **[Installation and usage](#installation-and-usage)** | -**[Code style](#the-black-code-style)** | **[pyproject.toml](#pyprojecttoml)** | -**[Editor integration](#editor-integration)** | **[blackd](#blackd)** | -**[Version control integration](#version-control-integration)** | -**[Ignoring unmodified files](#ignoring-unmodified-files)** | **[Used by](#used-by)** | -**[Testimonials](#testimonials)** | **[Show your style](#show-your-style)** | +**[Code style](#the-black-code-style)** | **[Pragmatism](#pragmatism)** +**[pyproject.toml](#pyprojecttoml)** | **[Editor integration](#editor-integration)** | +**[blackd](#blackd)** | **[Version control integration](#version-control-integration)** +| **[Ignoring unmodified files](#ignoring-unmodified-files)** | **[Used by](#used-by)** +| **[Testimonials](#testimonials)** | **[Show your style](#show-your-style)** | **[Contributing](#contributing-to-black)** | **[Change Log](#change-log)** | **[Authors](#authors)** @@ -489,6 +489,47 @@ file that are not enforced yet but might be in a future version of the formatter - for arguments that default to `None`, use `Optional[]` explicitly; - use `float` instead of `Union[int, float]`. +## Pragmatism + +Early versions of _Black_ used to be absolutist in some respects. They took after its +initial author. This was fine at the time as it made the implementation simpler and +there were not many users anyway. Not many edge cases were reported. As a mature tool, +_Black_ does make some exceptions to rules it otherwise holds. This section documents +what those exceptions are and why this is the case. + +### The magic trailling comma + +_Black_ in general does not take existing formatting into account. + +However, there are cases where you put a short collection or function call in your code +but you anticipate it will grow in the future. + +For example: + +```py3 +TRANSLATIONS = { + "en_us": "English (US)", + "pl_pl": "polski", +} +``` + +Early versions of _Black_ used to ruthlessly collapse those into one line (it fits!). +Now, you can communicate that you don't want that by putting a trailing comma in the +collection yourself. When you do, _Black_ will know to always explode your collection +into one item per line. + +How do you make it stop? Just delete that trailing comma and _Black_ will collapse your +collection into one line if it fits. + +### r"strings" and R"strings" + +_Black_ normalizes string quotes as well as string prefixes, making them lowercase. One +exception to this rule is r-strings. It turns out that the very popular +[MagicPython](https://github.com/MagicStack/MagicPython/) syntax highlighter, used by +default by (among others) GitHub and Visual Studio Code, differentiates between +r-strings and R-strings. The former are syntax highlighted as regular expressions while +the latter are treated as true raw strings with no special semantics. + ## pyproject.toml _Black_ is able to read project-specific default values for its command line options diff --git a/docs/index.rst b/docs/index.rst index 4291de7..2fa910c 100644 --- a/docs/index.rst +++ b/docs/index.rst @@ -50,6 +50,7 @@ Contents installation_and_usage the_black_code_style + pragmatism pyproject_toml editor_integration blackd