Pretty-print values in the REPL by printing each item in a list or
attrset on a separate line. When possible, single-item lists and
attrsets are printed on one line, as long as they don't contain a nested
list, attrset, or thunk.
Before:
```
{ attrs = { a = { b = { c = { }; }; }; }; list = [ 1 ]; list' = [ 1 2 3 ]; }
```
After:
```
{
attrs = {
a = {
b = {
c = { };
};
};
};
list = [ 1 ];
list' = [
1
2
3
];
}
```
Some tools which consume the "nix print-dev-env" rc script (such as
"nix-direnv") are sensitive to the use of unbound variables. They use
"set -u".
The "nix print-dev-env" rc script initially unsets "shellHook", then
loads variables from the derivation, and then evaluates "shellHook".
However, most derivations don't have a "shellHook" attribute.
So users get the error "shellHook: unbound variable". This can be
demonstrated with the command:
nix print-dev-env nixpkgs#hello | bash -u
This commit changes the rc script to provide an empty fallback value
for the "shellHook" variable.
Closes: #7951#8253
It is entirely possible for the path to be an empty string and many
unit tests actually pass it as an empty string (e.g. both_roundrip or
turnsEmptyPathIntoCWD). In this case, without this patch, absPath will
perform a one-byte out-of-bounds access.
This was discovered while enabling the nix test suite on Alpine where
we compile all software with `-D_GLIBCXX_ASSERTIONS=1`, thus resulting
in a test failure on Alpine.
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`.
Previously, the "file:./" prefix was not correctly recognized in
fixGitURL; instead, it was mistaken as a file path, which resulted in a
parsed url of the form "file://file:./".
This commit fixes the issue by properly detecting the "file:" prefix.
Note, however, that unlike "file://", the "file:./" URI is _not_
standardized, but has been widely used to referred to relative file
paths. In particular, the "git+file:./" did work for nix<=2.18, and was
broken since nix 2.19.0.
Finally, this commit fixes the issue completely for the 2.19 series, but
is still inadequate for the 2.20 series due to new behaviors from the
switch to libgit2. However, it does improve the correctness of parsing
even though it is not yet a complete solution.
