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libexpr: Support structured error classes

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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`.
This commit is contained in:
Rebecca Turner 2024-01-22 17:08:29 -08:00
parent c62c21e29a
commit c6a89c1a16
No known key found for this signature in database
40 changed files with 653 additions and 545 deletions
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22
src/libexpr/primops/fetchClosure.cc
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@ -27,7 +27,7 @@ static void runFetchClosureWithRewrite(EvalState & state, const PosIdx pos, Stor
state.store->printStorePath(fromPath),
state.store->printStorePath(rewrittenPath),
state.store->printStorePath(*toPathMaybe)),
.errPos = state.positions[pos]
.pos = state.positions[pos]
});
if (!toPathMaybe)
throw Error({
@ -36,7 +36,7 @@ static void runFetchClosureWithRewrite(EvalState & state, const PosIdx pos, Stor
"Use this value for the 'toPath' attribute passed to 'fetchClosure'",
state.store->printStorePath(fromPath),
state.store->printStorePath(rewrittenPath)),
.errPos = state.positions[pos]
.pos = state.positions[pos]
});
}
@ -54,7 +54,7 @@ static void runFetchClosureWithRewrite(EvalState & state, const PosIdx pos, Stor
"The 'toPath' value '%s' is input-addressed, so it can't possibly be the result of rewriting to a content-addressed path.\n\n"
"Set 'toPath' to an empty string to make Nix report the correct content-addressed path.",
state.store->printStorePath(toPath)),
.errPos = state.positions[pos]
.pos = state.positions[pos]
});
}
@ -80,7 +80,7 @@ static void runFetchClosureWithContentAddressedPath(EvalState & state, const Pos
"to the 'fetchClosure' arguments.\n\n"
"Note that to ensure authenticity input-addressed store paths, users must configure a trusted binary cache public key on their systems. This is not needed for content-addressed paths.",
state.store->printStorePath(fromPath)),
.errPos = state.positions[pos]
.pos = state.positions[pos]
});
}
@ -103,7 +103,7 @@ static void runFetchClosureWithInputAddressedPath(EvalState & state, const PosId
"The store object referred to by 'fromPath' at '%s' is not input-addressed, but 'inputAddressed' is set to 'true'.\n\n"
"Remove the 'inputAddressed' attribute (it defaults to 'false') to expect 'fromPath' to be content-addressed",
state.store->printStorePath(fromPath)),
.errPos = state.positions[pos]
.pos = state.positions[pos]
});
}
@ -154,14 +154,14 @@ static void prim_fetchClosure(EvalState & state, const PosIdx pos, Value * * arg
else
throw Error({
.msg = hintfmt("attribute '%s' isn't supported in call to 'fetchClosure'", attrName),
.errPos = state.positions[pos]
.pos = state.positions[pos]
});
}
if (!fromPath)
throw Error({
.msg = hintfmt("attribute '%s' is missing in call to 'fetchClosure'", "fromPath"),
.errPos = state.positions[pos]
.pos = state.positions[pos]
});
bool inputAddressed = inputAddressedMaybe.value_or(false);
@ -172,14 +172,14 @@ static void prim_fetchClosure(EvalState & state, const PosIdx pos, Value * * arg
.msg = hintfmt("attribute '%s' is set to true, but '%s' is also set. Please remove one of them",
"inputAddressed",
"toPath"),
.errPos = state.positions[pos]
.pos = state.positions[pos]
});
}
if (!fromStoreUrl)
throw Error({
.msg = hintfmt("attribute '%s' is missing in call to 'fetchClosure'", "fromStore"),
.errPos = state.positions[pos]
.pos = state.positions[pos]
});
auto parsedURL = parseURL(*fromStoreUrl);
@ -189,13 +189,13 @@ static void prim_fetchClosure(EvalState & state, const PosIdx pos, Value * * arg
!(getEnv("_NIX_IN_TEST").has_value() && parsedURL.scheme == "file"))
throw Error({
.msg = hintfmt("'fetchClosure' only supports http:// and https:// stores"),
.errPos = state.positions[pos]
.pos = state.positions[pos]
});
if (!parsedURL.query.empty())
throw Error({
.msg = hintfmt("'fetchClosure' does not support URL query parameters (in '%s')", *fromStoreUrl),
.errPos = state.positions[pos]
.pos = state.positions[pos]
});
auto fromStore = openStore(parsedURL.to_string());