Add removeprefix/removesuffix to string

[fmeum]

The names and behavior of the new functions removeprefix and removesuffix are consistent with PEP 616.

Fixes #185.

[fmeum]

@adonovan I added the new methods in alphabetical order rather than adjacent to endswith. Please let me know if I should change that.

[fmeum]

The CI fails with with an errors that seems unrelated:

Error in fail: error running 'git fetch origin master:origin/master' while working with @starlark-rust:
fatal: Couldn't find remote ref master

[laurentlb]

The change looks good to me.

Edit: Implementation in Java: bazelbuild/bazel#14824

[laurentlb]

This one looks wrong

[fmeum]

Sorry, got argument and return value mixed up. Should be fixed now.

[fmeum]

The change looks good to me.

Edit: Implementation in Java: bazelbuild/bazel#14824

According to #185 (comment), they are also available in Rust Starlark.

Edit: They indeed are since facebook/starlark-rust@7a7ef4b.

[laurentlb]

I think we need to fix the tests (in a separate PR) before we can merge this.

(or we'll need an admin)

[adonovan]

LGTM

[fmeum]

@adonovan @laurentlb Only just noticed that there is #193, which has more details and added the methods to one more ToC. Should that one be merged instead?

[laurentlb]

Done.

Thanks a lot for your help!

[tetromino]

The spec change contradicts PEP 616: if the string does not have a prefix/suffix, we want to (as in PEP 616) return a copy of the string, not the original string.

Do we really want foo.removesuffix(".so") += ".dll" to sometimes mutate foo and sometimes not?

[adonovan]

The spec change contradicts PEP 616: if the string does not have a prefix/suffix, we want to (as in PEP 616) return a copy of the string, not the original string.

Do we really want foo.removesuffix(".so") += ".dll" to sometimes mutate foo and sometimes not?

Starlark doesn't have a notion of string identity, so you can't distinguish the original from a copy. That said, it would be more precise to express it as: S.removeprefix(prefix) returns the portion of S after the prefix prefix, if S starts with that prefix, otherwise it returns S.

[laurentlb]

to sometimes mutate foo and sometimes not?

Strings are immutable in Starlark.