Allows checking directory entry type of a single file/directory.
This was added to optimize the use of `builtins.readDir` on some
filesystems and operating systems which cannot detect this information
using POSIX's `readdir`.
Previously `builtins.readDir` would eagerly use system calls to lookup
these filetypes using other interfaces; this change makes these
operations lazy in the attribute values for each file with application
of `builtins.readFileType`.
The original `builtins.getContext` test from
1d757292d0 would have caught this. The
problem is that b30be6b450 adding
`builtins.appendContext` modified that test to make it test too much at
once, rather than adding a separate test.
We now have isolated tests for both functions, and also a property test
showing everything put together (in the form of an eta rule for strings
with context). This is better coverage and properly reproduces the bug.
This is a really old test case (which was originally written before the
proper Nix syntax). The tested deep comparison behavior was implemented
and reverted soon after due to performance problems, but it has been
restored in today's Nix again (thanks to the derivation comparison
optimization, presumably).
* Clarify the documentation of foldl': That the arguments are forced
before application (?) of `op` is necessarily true. What is important
to stress is that we force every application of `op`, even when the
value turns out to be unused.
* Move the example before the comment about strictness to make it less
confusing: It is a general example and doesn't really showcase anything
about foldl' strictness.
* Add test cases which nail down aspects of foldl' strictness:
* The initial accumulator value is not forced unconditionally.
* Applications of op are forced.
* The list elements are not forced unconditionally.
This commit adds a test covering the discrepancy between parseDrvName's
implementation and documentation (the discrepancy was eliminated in the previous
commit).
if we defer the duplicate argument check for lambda formals we can use more
efficient data structures for the formals set, and we can get rid of the
duplication of formals names to boot. instead of a list of formals we've seen
and a set of names we'll keep a vector instead and run a sort+dupcheck step
before moving the parsed formals into a newly created lambda. this improves
performance on search and rebuild by ~1%, pure parsing gains more (about 4%).
this does reorder lambda arguments in the xml output, but the output is still
stable. this shouldn't be a problem since argument order is not semantically
important anyway.
before
nix search --no-eval-cache --offline ../nixpkgs hello
Time (mean ± σ): 8.550 s ± 0.060 s [User: 6.470 s, System: 1.664 s]
Range (min … max): 8.435 s … 8.666 s 20 runs
nix eval -f ../nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix
Time (mean ± σ): 346.7 ms ± 2.1 ms [User: 312.4 ms, System: 34.2 ms]
Range (min … max): 343.8 ms … 353.4 ms 20 runs
nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.720 s ± 0.031 s [User: 2.415 s, System: 0.231 s]
Range (min … max): 2.662 s … 2.780 s 20 runs
after
nix search --no-eval-cache --offline ../nixpkgs hello
Time (mean ± σ): 8.462 s ± 0.063 s [User: 6.398 s, System: 1.661 s]
Range (min … max): 8.339 s … 8.542 s 20 runs
nix eval -f ../nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix
Time (mean ± σ): 329.1 ms ± 1.4 ms [User: 296.8 ms, System: 32.3 ms]
Range (min … max): 326.1 ms … 330.8 ms 20 runs
nix eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system'
Time (mean ± σ): 2.687 s ± 0.035 s [User: 2.392 s, System: 0.228 s]
Range (min … max): 2.626 s … 2.754 s 20 runs
nixpkgs can save a good bit of eval memory with this primop. zipAttrsWith is
used quite a bit around nixpkgs (eg in the form of recursiveUpdate), but the
most costly application for this primop is in the module system. it improves
the implementation of zipAttrsWith from nixpkgs by not checking an attribute
multiple times if it occurs more than once in the input list, allocates less
values and set elements, and just avoids many a temporary object in general.
nixpkgs has a more generic version of this operation, zipAttrsWithNames, but
this version is only used once so isn't suitable for being the base of a new
primop. if it were to be used more we should add a second primop instead.
Otherwise the result of the printing can't be parsed back correctly by
Nix (because the unescaped `${` will be parsed as the begining of an
anti-quotation).
Fix#3989
This allows querying the location of function arguments. E.g.
builtins.unsafeGetAttrPos "x" (builtins.functionArgs ({ x }: null))
=> { column = 57; file = "/home/infinisil/src/nix/inst/test.nix"; line = 1; }
As fromTOML supports \u and \U escapes, bring fromJSON on par. As JSON defaults
to UTF-8 encoding (every JSON parser must support UTF-8), this change parses the
`\u hex hex hex hex` sequence (\u followed by 4 hexadecimal digits) into an
UTF-8 representation.
Add a test to verify correct parsing, using all escape sequences from json.org.
For text files it is possible to do it like so:
`builtins.hashString "sha256" (builtins.readFile /tmp/a)`
but that doesn't work for binary files.
With builtins.hashFile any kind of file can be conveniently hashed.
