lix/tests
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
..
functional libexpr: Support structured error classes 2024-02-01 16:39:38 -08:00
installer updated store ping to store info in files 2023-10-18 00:14:11 +05:30
nixos nixos/tests/remote-builds*: Format 2024-01-22 18:47:59 +01:00
unit libexpr: Support structured error classes 2024-02-01 16:39:38 -08:00