Building a Python package doesn't work as advertised

[homfunc]

Checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pixi, using pixi --version.

Reproducible example

Trying to follow the Tutorial Building a Python package for v0.39.5 with the pixi.toml and pyproject.toml from that example (for definiteness I include them here)

pyproject.toml

[project]
dependencies = ["rich"]                               
name = "rich_example"
requires-python = ">= 3.11"
scripts = { rich-example-main = "rich_example:main" } 
version = "0.1.0"

[build-system] 
build-backend = "hatchling.build"
requires = ["hatchling"]

pixi.toml

[workspace] 
channels = ["https://prefix.dev/conda-forge"]
platforms = ["osx-arm64",]
preview = ["pixi-build"]

[dependencies] 
rich_example = { path = "." }

[tasks] 
start = "rich-example-main"

[package] 
name = "rich_example"
version = "0.1.0"

[build-system] 
build-backend = { name = "pixi-build-python", version = "*" }
channels = [
  "https://prefix.dev/pixi-build-backends",
  "https://prefix.dev/conda-forge",
]

[host-dependencies] 
hatchling = "==1.26.3"

[run-dependencies] 
rich = ">=13.9.4,<14"

Issue description

Running pixi install --verbose produces an error complaining about a missing field

❯ pixi install --verbose
 INFO pixi::environment: verifying prefix location is unchanged, with prefix file: /Users/anonymous/test-pixi/.pixi/envs/conda-meta/pixi_env_prefix
 INFO pixi::lock_file::outdated: environment 'default' is out of date because the channels in the lock-file do not match the environments channels
 INFO pixi::repodata: repodata gateway: using max '50' concurrent network requests
 INFO resolve_conda{group=default platform=osx-arm64}:extract_records{source=. platform=osx-arm64}: pixi_build_frontend::build_frontend: discovered a pixi source package at /Users/anonymous/test-pixi
Error: 
  × failed to extract metadata for 'rich_example'
  ├─▶ received invalid response from the build backend (pixi-build-python) when calling 'initialize'
  ╰─▶ missing field `capabilities`

Expected behavior

Python package is built without error.

[ruben-arts]

The latest version of pixi-build-python is already out of sync with pixi's latest release. You could try with version = "0.1.0dev20250106162308"

[homfunc]

Thanks @ruben-arts. I can confirm that the updated example in Building a Python package (dev) works with the pixi build on branch main 5329f488d8c69167705214d81fa7e993e75f512b.

For posterity here is the

pixi.toml

[workspace] 
channels = [
  "https://prefix.dev/conda-forge"
]
platforms = ["osx-arm64", ]
preview = ["pixi-build"]

[dependencies]
rich_example = { path = "." }

[tasks] 
start = "rich-example-main"

[package] 
name = "rich_example"
version = "0.1.0"

[package.build]
backend = { name = "pixi-build-python", version = "0.1.0dev20250107152721" }
# backend = { name = "pixi-build-python", version = "*" }
channels = [
  "https://prefix.dev/pixi-build-backends",
  "https://prefix.dev/conda-forge",
]

[package.host-dependencies] 
hatchling = "==1.26.3"

[package.run-dependencies] 
rich = ">=13.9.4,<14"

I tested with both latest ("*") and "0.1.0dev20250107152721" - both worked

❯ pixi install --verbose
 INFO pixi::environment: verifying prefix location is unchanged, with prefix file: /Users/anonymous/test-pixi/.pixi/envs/conda-meta/pixi_env_prefix
 INFO pixi::lock_file::outdated: environment 'default' is out of date because it does not exist in the lock-file.
 INFO pixi::repodata: repodata gateway: using max '50' concurrent network requests
 INFO resolve_conda{group=default platform=osx-arm64}: pixi::lock_file::update: fetched 1010 records in 355.905375ms
 INFO pixi::lock_file::update: resolved conda environment for environment 'default' 'osx-arm64' in 366ms 95us 208ns
 INFO pixi::lock_file::update: Updating prefix
 INFO pixi::environment: No update needed for the prefix file.
 INFO pixi::environment: Verify history file exists: /Users/anonymous/test-pixi/.pixi/envs/default/conda-meta/history
 INFO pixi::lock_file::resolve::uv_resolution_context: uv keyring provider is disabled
✔ The default environment has been installed.
❯ pixi run rich-example-main
┏━━━━━━━━━━━━━━┳━━━━━┳━━━━━━━━━━━━━┓
┃ name         ┃ age ┃ city        ┃
┡━━━━━━━━━━━━━━╇━━━━━╇━━━━━━━━━━━━━┩
│ John Doe     │ 30  │ New York    │
│ Jane Smith   │ 25  │ Los Angeles │
│ Tim de Jager │ 35  │ Utrecht     │
└──────────────┴─────┴─────────────┘

I'm happy to close this with the next release.