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nix/src/libmain
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
..
common-args.cc Split up util.{hh,cc} 2023-11-05 12:20:02 -05:00
common-args.hh nix: Support the --repair flag 2023-04-28 17:03:04 +02:00
local.mk Use buildprefix in a few more places 2023-11-29 19:49:07 -05:00
loggers.cc Split up util.{hh,cc} 2023-11-05 12:20:02 -05:00
loggers.hh Ensure all headers have #pragma once and are in API docs 2023-03-31 23:19:44 -04:00
nix-main.pc.in Fix building with GCC 9 2023-02-10 18:38:57 +01:00
progress-bar.cc Show Git fetch progress 2023-11-15 13:57:20 +01:00
progress-bar.hh Ensure all headers have #pragma once and are in API docs 2023-03-31 23:19:44 -04:00
shared.cc libexpr: Support structured error classes 2024-02-01 16:39:38 -08:00
shared.hh Split up util.{hh,cc} 2023-11-05 12:20:02 -05:00
stack.cc libmain: Make the entire stack overflow handler pluggable 2022-10-14 12:53:46 +02:00