poetry add breaks existing [build-system]

• I am on the latest Poetry version.

• I have searched the issues of this repo and believe that this is not a duplicate.

• If an exception occurs when executing a command, I executed it again in debug mode (-vvv option).

• OS version and name: DISTRIB_ID=Ubuntu DISTRIB_RELEASE=20.04

• Poetry version: Poetry version 1.0.10

• Link of a Gist with the contents of your pyproject.toml file: https://gist.github.com/ycd/2311f6e9a48cb7e1e8811c87247dc3a6

Issue

When adding a new dependency with poetry add example[extra1, extra2] it tries to override existing [build-system] and breaks it.

[build-system]
requires = ["poetry>=0.12"]
build-backend = "poetry.masonry.api"

Also streamable link: https://streamable.com/xwvej8

[abn]

Had a quick look, it’s a bug in how we parse the name. That should really change and be normalised in core.

[jaklan]

@abn the biggest issue is resolved, but it’s not yet working correctly (I’m using the latest pre-release). That’s the end of my pyproject.toml (I concatenate two pyproject.toml files during project generation with cookiecutter - one with poetry stuff, ending with [build-system] table, and another one with tool configs like isort):

[build-system]
requires = ["poetry-core>=1.0.0a5"]
build-backend = "poetry.core.masonry.api"

[tool.isort]
sections = ["FUTURE", "STDLIB", "THIRDPARTY", "FIRSTPARTY", "LOCALFOLDER"]
known_first_party = ["some_package"]
profile = "black"

Then, when I run poetry add ... during development, TOML tables are automatically reordered, but there’s an empty line missing between tables:

[tool.isort]
sections = ["FUTURE", "STDLIB", "THIRDPARTY", "FIRSTPARTY", "LOCALFOLDER"]
known_first_party = ["some_package"]
profile = "black"
[build-system]
requires = ["poetry-core>=1.0.0a5"]
build-backend = "poetry.core.masonry.api"

To make it work properly, you have to have an additional empty line at the end of the file, but it would be really annoying to especially exclude pyproject.toml from end-of-file-fixer pre-commit hook to fix this behaviour. Regardless of the error - I don’t really understand what’s the reason behind that reordering behaviour?