nix/tests/functional/lang/eval-fail-fromTOML-timestamps.err.exp at d9684664c8693b3f1d1ad69b6ed3dbce363748b0 - NixOS/nix - forgejo

NixOS/nix

mirror of https://github.com/NixOS/nix synced 2024-09-19 23:03:53 -04:00

Rebecca Turner c6a89c1a16

libexpr: Support structured error classes

While preparing PRs like #9753, I've had to change error messages in
dozens of code paths. It would be nice if instead of

    EvalError("expected 'boolean' but found '%1%'", showType(v))

we could write

    TypeError(v, "boolean")

or similar. Then, changing the error message could be a mechanical
refactor with the compiler pointing out places the constructor needs to
be changed, rather than the error-prone process of grepping through the
codebase. Structured errors would also help prevent the "same" error
from having multiple slightly different messages, and could be a first
step towards error codes / an error index.

This PR reworks the exception infrastructure in `libexpr` to
support exception types with different constructor signatures than
`BaseError`. Actually refactoring the exceptions to use structured data
will come in a future PR (this one is big enough already, as it has to
touch every exception in `libexpr`).

The core design is in `eval-error.hh`. Generally, errors like this:

    state.error("'%s' is not a string", getAttrPathStr())
      .debugThrow<TypeError>()

are transformed like this:

    state.error<TypeError>("'%s' is not a string", getAttrPathStr())
      .debugThrow()

The type annotation has moved from `ErrorBuilder::debugThrow` to
`EvalState::error`.

2024-02-01 16:39:38 -08:00

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 error:
        … while calling the 'fromTOML' builtin
          at /pwd/lang/eval-fail-fromTOML-timestamps.nix:1:1:
 | builtins.fromTOML ''
              | ^
 |   key = "value"
        error: while parsing TOML: Dates and times are not supported