The current instructions tell users to perform two actions:
- update the package database
- install the jq package
The only thing users need to or should be doing is actually installing
the jq package -- regardless of which version is being installed.
Guidelines on how to perform system updates are massively out of scope.
In the case of partially performing a system update as a prerequisite
for installing jq, the official guidance from Arch Linux is not to do
this: partial updates are not supported, we refuse to support them, and
anyone who does try to perform them anyway is assumed to know so much
about their system that they clearly do not ever need help from anyone
else (which is a good thing since they won't get it). The result is a
frankensteined system that can only ever be supported by the person who
frankensteined it to begin with. The only reason the package manager
even allows it to occur in the first place is because other
distributions using pacman might have different LTS policies, and
because it would prevent expert users from being in control of their
system, as per the traditional Unix philosophy:
"Unix was not designed to stop you from doing stupid things, because
that would also stop you from doing clever things."
Consequences of performing partial updates without understanding the
ramifications in extensive detail can include breaking the partially
updated application (jq), breaking any application that shares a mutual
dependency with the partially updated application (which jq is *lucky*
to only depend on the ever-backwards-compatible glibc), or breaking the
entire operating system by leaving armed traps behind for the next time
a `pacman -S new-package` is executed and thereby breaks *its* cascading
dependencies.
See:
https://wiki.archlinux.org/index.php/System_maintenance#Partial_upgrades_are_unsupported
The current paragraph is not complete, since a digit is not a special character.
Changing it to:
If the key contains special characters or starts with a digit,
you need to surround it with double quotes like this:
`."foo$"`, or else `.["foo$"]`.
Users are often surprised by the requirement to parenthesize any
non-trivial object key expressions in object constructors. E.g.,
{"a"+"b":1}. This commit adds one more kind of key expression besides
literals and idents: variable references.
A common use case for this is jq programs as JSON templates to fill in
with variables computed from inputs or passed in on the command-line.
E.g., {some_key:$value}. Now users can also use, e.g., {$key:$value}.
This and the restrictions on key and value expressions in object
constructors are now clarified a bit in the documentation.
This reverts commit e24af3c78e78a3aab05a2800d825d56f1d842b1b.
While the semantics are desirable, there is no way to implement them
efficiently. The reason is that in order to handle backtracking (empty)
from the state update expression, we have to retain a reference to the
reduction state value in order to restore it upon backtracking.
Retaining a reference to the reduction state kills performance by
causing lots of additional memory allocations and garbage because the
input to the update expression will always have at least two references,
thus no changes to it can be done in-place, and all changes end up being
CoW changes.
Avoiding this is the very reason for the LOADVN instruction (leaving
`null` in the variable loaded from).
This has been a complicated issue to fix for a number of reasons.
The core of it is that the behavior is different between different
versions of macOS, some of which set possible-but-incorrect values.
This commit addresses the issue by always using our computation for
tm_wday and tm_yday on macOS. As a side-effect, strptime format
strings that specify %u and %j will no longer work on macOS.
strptime() on OS X and *BSDs (reputedly) does not set tm_wday and
tm_yday unless corresponding %U and %j format specifiers were used.
That can be... surprising when one parsed year, month, and day anyways.
Glibc's strptime() conveniently sets tm_wday and tm_yday in those cases,
but OS X's does not, ignoring them completely.
This commit makes jq compute those where possible, though the day of
week computation may be wrong for dates before 1900-03-01 or after
2099-12-31.
Now that #1313 is fixed, |= no longer outputs null when the RHS update
expression outputs empty.
When a user wants to keep the current value of the LHS they would have
the RHS update expression output `.`, so having `empty` achieve the same
thing would be redundant. The obvious thing to do is to delete the LHS
when the RHS update outputs `empty` (i.e., doesn't output any values).
It's reasonable to think that existing programs won't be broken by this
change, because reduce and |= not handling empty well is clearly a bug.
(Though it's possible that some programs were using empty to quickly
terminate reduce or |=, it's not likely. They should use label/break
instead.)
Prior to this change |= would use the _last_ value output by the RHS
update expression. With this change |= will use the _first_ value
instead. This change _is_ a minor backwards-incompatible change. It
may or may not be acceptable; we'll see. It is a useful change in that
it makes |= faster when the update expression produces multiple values.
