build backend toml parse failure on pyproject readme

[CoderJoshDK]

Summary

When upgrading one of my packages to use the new build backend, I got the following error:

Resolved 20 packages in 1ms
  × Failed to build `wiopy @ file:///Users/joshie/Dev/projects/github/Walmart%20Wrapper`
  ├─▶ The build backend returned an error
  ╰─▶ Call to `uv_build.build_editable` failed (exit status: 1)

      [stderr]
      Error: Invalid pyproject.toml

      Caused by:
          TOML parse error at line 6, column 10
            |
          6 | readme = {file = "README.md", content-type = "text/markdown"}
            |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
          data did not match any variant of untagged enum Readme


      Stack backtrace:
         0: __mh_execute_header
         1: __mh_execute_header
         2: __mh_execute_header
         3: __mh_execute_header
         4: __mh_execute_header

      hint: This usually indicates a problem with the package or the build environment.

This parsing error should likely not happen. Looking at the packaging docs, this pattern seems possible. Because the file ends in md, I will modify my pyproject to be just readme = "README.md; but I figured this was still work raising.

To reproduce:

uv init --package test
cd test
vim pyproject.toml  # modify readme setting to match `readme = {file = "README.md", content-type = "text/markdown"}`

Platform

Darwin 24.5.0 arm64

Version

uv 0.8.0 (Homebrew 2025-07-17)

Python version

Python 3.13.5

[charliermarsh]

Thanks, will take a look.

[charliermarsh]

Thank you, fixed in #14762.