This just goes back until it finds an existent path, resolves that,
and adds the normalized rest on top.
So if you try
/bin/foo/bar////../baz
and /bin exists as a symlink to /usr/bin, it would resolve that, and
normalize the rest, giving
/usr/bin/foo/baz
(note: We might want to add this to realpath as well?)
This includes the "." in what `path extension` prints.
This allows distinguishing between an empty extension (just `.`) and a
non-existent extension (no `.` at all).
This adds a "path" builtin that can handle paths.
Implemented so far:
- "path filter PATHS", filters paths according to existence and optionally type and permissions
- "path base" and "path dir", run basename and dirname, respectively
- "path extension PATHS", prints the extension, if any
- "path strip-extension", prints the path without the extension
- "path normalize PATHS", normalizes paths - removing "/./" components
- and such.
- "path real", does realpath - i.e. normalizing *and* link resolution.
Some of these - base, dir, {strip-,}extension and normalize operate on the paths only as strings, so they handle nonexistent paths. filter and real ignore any nonexistent paths.
All output is split explicitly, so paths with newlines in them are
handled correctly. Alternatively, all subcommands have a "--null-input"/"-z" and "--null-output"/"-Z" option to handle null-terminated input and create null-terminated output. So
find . -print0 | path base -z
prints the basename of all files in the current directory,
recursively.
With "-Z" it also prints it null-separated.
(if stdout is going to a command substitution, we probably want to
skip this)
All subcommands also have a "-q"/"--quiet" flag that tells them to skip output. They return true "when something happened". For match/filter that's when a file passed, for "base"/"dir"/"extension"/"strip-extension" that's when something about the path *changed*.
Filtering
---------
`filter` supports all the file*types* `test` has - "dir", "file", "link", "block"..., as well as the permissions - "read", "write", "exec" and things like "suid".
It is missing the tty check and the check for the file being non-empty. The former is best done via `isatty`, the latter I don't think I've ever seen used.
There currently is no way to only get "real" files, i.e. ignore links pointing to files.
Examples
--------
> path real /bin///sh
/usr/bin/bash
> path extension foo.mp4
mp4
> path extension ~/.config
(nothing, because ".config" isn't an extension.)
This teaches `--on-signal SIGINT` (and by extension `trap cmd SIGINT`)
to work properly in scripts, not just interactively. Note any such
function will suppress the default behavior of exiting. Do this for
SIGTERM as well.
Like `set` and `read` before it, `eval` can be used to set variables,
and so it can't be shadowed by a function without loss of
functionality.
So this forbids it.
Incidentally, this means we will no longer try to autoload an
`eval.fish` file that's left over from an old version, which would
have helped with #8963.
Previously, running `fish_add_path /foo /foo` would result in /foo
being added to $PATH twice.
Now we check that it hasn't already been given, so we skip the
second (and any further) occurence.
This *might* be a bit faster running under TSAN, otherwise it takes >
400 seconds on Github Actions.
If this doesn't work we need to disable it for TSAN.
Curses variables like `enter_italics_mode` are secretly defined to
dereference through the `cur_term` variable. Be sure we do not read or
write these curses variables if cur_term is NULL. See #8873, #8875.
Add a regression test.
To recap, this means `&` in the middle of a word no longer
backgrounds.
So:
```fish
echo foo&bar # prints foo&bar
echo foo& bar # backgrounds an echo that prints "foo" and runs "bar"
```
This can no longer be changed. If "no-stderr-nocaret" is in
$fish_features it will simply be ignored.
The "^" redirection that was deprecated in fish 3.0 is now gone for good.
Note: For testing reasons, it can still be set _internally_ by running
"feature_flags_t::set". We simply shouldn't do that.
Prior to this change, if you tab-completed a token with a wildcard (glob), we
would invoke ordinary completions. Instead, expand the wildcard, replacing
the wildcard with the result of expansions. If the wildcard fails to expand,
flash the command line to signal an error and do not modify it.
Example:
> touch file(seq 4)
> echo file*<tab>
becomes:
> echo file1 file2 file3 file4
whereas before the tab would have just added a space.
Some things to note:
1. If the expansion would produce more than 256 items, we flash the command
line and do nothing, since it would make the commandline overfull.
2. The wildcard token can be brought back through Undo (ctrl-Z).
3. This only kicks in if the wildcard is in the "path component
containing the cursor." If the wildcard is in a previous component,
we continue using completions as normal.
Fixes#954.
When you do
```fish
set foo-bar baz
```
"foo-baz" isn't usable as a variable *name*. When you just say the
"variable" is invalid that could also be interpreted to be a special
type of variable or something.
String tokens are subdivided by command substitutions. Some syntax errors
can occur in the gap between two command substitutions. Make the caret point
to the start of that gap, instead of the token start.
When expanding command substitutions, we use a naïve way of detecting whether
the cmdsub has the optional leading dollar. We check if the last character was
a dollar, which breaks if it's an escaped dollar. We wrongly expand
\$(echo "") to the empty string. Fix this by checking if the dollar was escaped.
The parse_util_* functions have a bunch of output parameters. We should
return a parameter bag instead (I think I tried once and failed).
Given
set var a
echo "$var$(echo b)"
the double-quoted string is expanded right-to-left, so we construct an
intermediate "$varb". Since the variable "varb" is undefined, this wrongly
expands to the empty string (should be "ab"). Fix this by isolating the
expanded command substitution internally. We do the same when handling
unquoted command substitutions.
Fixes#8849
The read test is now failing on GitHub actions even though it passes on
my Mac. It may be due to differences in dd between these two
environments. Stop using dd and just use head.
The read.fish check has a test where it limits the amount of data passed to
`read` to 8192 bytes, and verifies that fish reads exactly that amount.
This check occasionally fails on the OBS builds; it's very hard to repro a
failure locally, but I finally did it.
The amount of data written is limited via `yes` and `dd`:
yes $line | dd bs=1024 count=(math "$fish_read_limit / 1024")
The bug is that `dd` outputs a fixed number of "blocks" where a block
corresponds to a single read. As `yes` and `dd` are running concurrently,
it may happen that `dd` performs a short read; this then counts as a single
block. So `dd` may output less than the desired amount of data.
This can be verified by removing the 2>/dev/null redirection; on a
successful run dd reports `8+0 records out`, on a failed run it reports
`7+1 records out` because one of the records was short.
Fix this by using `fullblock` so that dd will no longer count a short read
as a single block. `head` would probably be a simpler tool to use but we'll
do this for now.
Happily it's not a fish bug. No need to relnote it.
This was already apparently supposed to work, but didn't because we
just overrode errno again.
This now means that, if a correctly named candidate exists, we don't
start the command-not-found handler.
See #8804
This used to call exec_subshell, which has two issues:
1. It creates a command substitution block which shows up in a stack
trace
2. It does much more work than necessary
This removes a useless "in command substitution" from an error message
in an autoloaded file, and it speeds up autoloading a bit (not
measurable in actual benchmarks, but microbenchmarks are 2x).
Cancellation groups were meant to reflect the following idea: if you ran a
simple block:
begin
cmd1
cmd2
end
then under job control, cmd1 and cmd2 would get separate groups; however if
either exits due to SIGINT or SIGQUIT we also want to propagate that to the
outer block. So the outermost block and its interior jobs would share a
cancellation group. However this is more complex than necessary; it's
sufficient for the execution context to just store an int internally.
This ought not to affect anything user-visible.
* Implement fish_wcstod_underscores
* Add fish_wcstod_underscores unit tests
* Switch to using fish_wcstod_underscores in tinyexpr
* Add tests for math builtin underscore separator functionality
* Add documentation for underscore separators for math builtin
* Add a changelog entry for underscore numeric separators
We can't always read in chunks because we often can't bear to
overread:
```fish
echo foo\nbar | begin
read -l foo
read -l bar
end
```
needs to have the first read read `foo` and the second read `bar`. So
here we can only read one byte at a time.
However, when we are directly redirected:
```fish
echo foo | read foo
```
we can, because the data is only for us anyway. The stream will be
closed after, so anything not read just goes away. Nobody else is
there to read.
This dramatically speeds up `read` of long lines through a pipe. How
much depends on the length of the line.
With lines of 5000 characters it's about 15x, with lines of 50
characters about 2x, lines of 5 characters about 1.07x.
See #8542.
This is the simple fix - if we have no valid digit, we have nothing to
return. So instead of returning a NULL, we return an error.
This is already the case for invalid octal escapes (like `\777`).
Fixes#8545
This reverts commits:
2d9e51b43ed1d9f147ec346ce8081b
The box drawing because it's entangled with the rest and we don't
currently use this anywhere I know of. Nor was it gated on terminfo,
so it could have broken things, for subjectively little gain.
Fixes#8727.
A history search ends when you move the cursor, but the commandline inserted by
history search is still marked as transient. This means that the next history
search will clear the transient commandline. This means we are dropping an undo
point, for example:
echo 11
echo 1
echo autosuggestion
echo^P # commandline is "echo 1"
^A # stop history search
^P # commandline is "echo 11"
^Z # Bug: commandline goes back to "echo", but it should be "echo 1"
In the worst case, we are switching from line-search to token-search (see
the attached test case). Clearing the transient edit means the line is gone
and only the token is left on the command line.
Say the user has a multi-char binding (typically an escape sequence), and a
signal arrives partway through the binding. The signal has an event handler
which enques some readline event, for example, `repaint`. Prior to this
change, the readline event would cause the multi-char binding to fail. This
would cause bits of the escape sequence to be printed to the screen.
Fix this by noticing when a sequence was "interrupted" by a non-char event,
and then rotating a sequence of such interruptions to the front of the
queue.
Fixes#8628
Today, a command like "var=val status " has custom completions
because we skip over the var=val variable override when detecting
the command token.
However if the custom completions read the commandline state (via
"commandline -opc") they do see they variable override, which breaks
them, most likely. Try "a=b git ".
For completions of wrapped commands, we already set a transient
commandline. Do the same for commands with leading variable overrides;
then git completions for "a=b git " will think the commandline is
"git ".
`read` allows specifying the initial command line text. This was
text got accidentally ignored starting in a32248277f. Fix this
regression and add a test.
Fixes#8633
Previously, when we got an unknown option with --ignore-unknown, we
would increment woptind but still try to read the same contents.
This means in e.g.
```
argparse -i h -- -ooo -h
```
The `-h` would also be skipped as an option, because after the first
`-o` getopt reads the other two `-o` and skips that many options.
This could be handled more extensively in wgetopt, but the simpler fix
is to just skip to the next argv entry once we have an unknown option
- there's nothing more we can do with it anyway!
Additionally, document this and clearly explain that we currently
don't transform the option.
Fixes#8637
fish_git_prompt may run certain git commands which may invoke certain
external programs as specified `.git/config`. Prevent this by suppressing
certain git config options.
This affects the caret position. In an expression like
123 456
we previously reported:
123 456
^ missing operator
Now we do:
123 456
^ missing operator
We do it on the first space, which should be acceptable.
(no need for a changelog entry, we have already ignored #8511)
Only show the shebang warning for .fish commands.
Use the phrase "interpreter directive" as the formal name for the
shebang.
Switch from windows to Windows for the operating system.
"not not return 34" exits with 34, not 1. This behavior is pretty
surprising but benign. I think it's very unlikely that anyone relies
on the opposite behavior, because using two "not" decorators in one
job is weird, and code that compares not's raw exit code is rare.
The behavior doesn't match our docs, but it's not worth changing the
docs because that would confuse newcomers. Add a test to cement the
behavior and a comment to explain this is intentional.
I considered adding the comment at
parse_execution_context_t::populate_not_process where this behavior
is implemented but the field defintion seems even better, because I
expect programmers to read that first.
Closes#8377
Commit e40eba358 (Treat text following quoted command substitution
as quoted) made parse_util_locate_cmdsubst_range() aware of quoted
command substitutions, by skipping surrounding text via quote_end().
However, it was not quite right. We fail to properly parse
two consecutive command substitutions in the same string,
because we don't maintain the quoting context across calls to
parse_util_locate_cmdsubst_range(). Let's track that bit in a
parameter. This allows us to get rid of the quote_end() hack.
Also apply this to the other place where we call
parse_util_locate_cmdsubst_range() in a loop (highlighting).
Fixes#8500
This fixes a regression about where we report errors:
echo error(here
old: ^
fixed: ^
Commit 0c22f67bd (Remove the old parser bits, 2020-07-02) removed
uses of "error_offset_within_token" so we always report errors at
token start. Add it back, hopefully restoring the 3.1.2 behavior.
Note that for cases like
echo "$("
we report "unbalanced quotes" because we treat the $( as double
quote. Giving a better error seems hard because of the ambguity -
we don't know if quote is meant to be inside or outside the command
substitution.
If you make a script called `foo` somewhere in $PATH, and did not give
it a shebang, this would end up calling
sh foo
instead of
sh /usr/bin/foo
which might not match up.
Especially if the path is e.g. `--version` or `-` that would end up
being misinterpreted *by sh*.
So instead we simply pass the actual_cmd to sh, because we need it
anyway to get it to fail to execute before.
For some reason, the window dimension parameters are ignored by tmux.
Not even an extra "resize-pane -x 80 -y 10" helps. So let's just drop
that assumption from our tests.
When the completion pager fills up all lines of the screen, we subtract
from the pager size the number of lines occupied by the prompt +
command line buffer (typically 1), so the command line is always
visible. However, we only subtract the number of lines *before* the
cursor, so on some multiline commandlines we draw a pager that is
too large for our screen, clobbering the commandline rendering.
Fix this by counting all lines.
Fixes#8509
Possibly fixes#8405
A command like "printf nonewline | sed s/x/y/" does not print a
concluding newline, whereas "printf nnl | string replace x y" does.
This is an edge case -- usually the user input does have a newline at
the end -- but it seems still better for this command to just forward
the user's data.
Teach most string subcommands to check if stdin is missing the trailing
newline, and stop adding one in that case.
This does not apply when input is read from commandline arguments.
* Most subcommands stop adding the final newline, because they don't
really care about newlines, so besides their normal processing,
they just want to preserve user input. They are:
* string collect
* string escape/unescape
* string join¹
* string lower/upper
* string pad
* string replace
* string repeat
* string sub
* string trim
* string match keeps adding the newline, following "grep". Additionally,
for string match --regex, it's important to output capture groups
separated by newlines, resulting in multiple output lines for an
input line. So it is not obvious where to leave out the newline.
* string split/split0 keep adding the newline for the same reason --
they are meant to output multiple elements for a single input line.
¹) string join0 is not changed because it already printed a trailing
zero byte instead of the trailing newline. This is consistent
with other tools like "find -print0".
Closes#3847
A «complete -C '~/fish-shell/build/fish '» fails to load custom
completions because we do not expand the ~, so
complete_param_for_command() thinks that this command is invalid.
Expand command tokens before loading custom completions.
Fixes#8442
Currently,
set -q --unpath PATH
simply ignores the "--unpath" bit (and same for "--path").
This changes it, so just like exportedness you can check pathness.
* fish_key_reader: Simplify default output
It now only prints the bind statement. Timing information and such is
relegated to a separate "verbose" mode.
* Adjust fish_key_reader docs
* Adjust tests
This finds the first broken component, to help people figure out where
they misspelt something.
E.g.
```
echo foo >/usr/lob/systemd/system/machines.target.wants/var-lib-machines.mount
```
will now show:
```
warning: Path '/usr/lob' does not exist
```
which would help with seeing that it should be "/usr/lib".
On a commandline like "ls arg" (cursor at end) we do not expand
abbrevations on enter. OTOH, on "ls " we do expand. This can be
frustrating because it means that the two obvious ways to suppress
abbrevation expansion (C-Space or post-expansion C-Z) cannot be used to
suppress expansion of a command without arguments. (One workaround is
"ls #".)
Only expand-on-execute if the cursor is at the command name (no space
in between).
This is a strict improvement for realistic scenarios, because if there
is a space, the user has already expressed the intent to not expand
the abbreviation. (I hope no one is using recursive abbreviations.)
Closes#8423
This was supposed to act like `type -q` or `command -q`, in that it
returns 0 if at least 1 exists.
But because it used the wrong variable it didn't.
Fixes#8431.
This allows rebinding escape in the user list without breaking e.g.
arrow keys (which send escape and then `[A` and similar, so escape is
a prefix of them).
Fixes#8428.
This fixes printing octal and hex values that are negative or larger
than UINT_MAX.
Negative values get a leading -, like:
> math --base hex -10
-0xa
Fixes#8417.
Commit ec3d3a481 (Support "$(cmd)" command substitution without line
splitting, 2021-07-02) started treating an input string like
"a$()b" as if it were "a"$()"b". Yet, we do not actually insert the
virtual quotes. Instead we just adapted the definition of when quotes
are closed - hence the changes to quote_end().
parse_util_locate_cmdsubst_range() is aware
of the changes to quote_end() but some of its
callers like parse_util_detect_errors_in_argument() and
highlighter_t::color_as_argument() are not. They split strings at
command substitution boundaries without handling the special quoting
rules. (Only the expansion logic did it right.)
Fix this by handling the special quoting rules inside
parse_util_locate_cmdsubst_range(). This is a bit hacky since it
makes it harder for callers to process some substrings in between
command substitutions, but that's okay because current callers only
care about what's inside the command substitutions.
Fixes#8394
Since #4376, for-loops would set the loop variable outside, so it
stays valid.
They did this by doing the equivalent of
```fish
set -l foo $foo
for foo in 1 2 3
```
And that first imaginary `set -l` would also fire a set-event.
Since there's no use for it and the variable isn't actually set, we
remove it.
Fixes#8384.
widechar_width no longer classifies U+1F41F as widened-in-9, so the
width no longer changes.
Since we're interested in testing the change here, we need a different
emoji.
Just use 🥁, which was introduced in 9 as wide, and therefore widened
in 9.
fish might use XDG_RUNTIME_DIR for the uvar notifier fifo, so this
makes sure that tests are isolated.
Also set permissions to comply with the XDG basedir spec.
Like the $status commit, this would add the offset to already existing
errors, so
```fish
(foo)
(bar)
something
```
would see the "(foo)" error, store the correct error location, then
see the "(bar)" error, and *add the offset of (bar)* to the "(foo)"
error location.
Solve this by making a new error list and appending it to the existing
ones.
There's a few other ways to solve this, including:
- Stopping after the first error (we only display the first anyway, I
think?)
- Making it so the source location has an "absolute" flag that shows
the offset has already been added (but do we ever need to add two offsets?)
I went with the simpler fix.
This would break the location of any prior errors without doing
anything of value.
E.g.
```fish
echo foo | exec grep # this exec is not allowed!
$status
somethingelse # The error might be found here!
```
Would apply the offset of `$status` to the offset of `exec`, locating
the error for `exec` somewhere after $status!
Prior to this change, tmux based tests would call 'isolated-tmux' which would
initialize tmux on first call, an admitted "evil hack." Switch to requiring
an explicit call to 'isolated-tmux-start' which then defines 'isolated-tmux'
and other functions. Add some loop-until-prompt logic into
'isolated-tmux-start'. This improves reliability of the tmux tests on systems
under load; at least it makes the tests pass in the background on my Mac.
Remove the '$sleep' variable, to be replaced with 'tmux-sleep'.
This makes it so we treat backspaces as width -1, but never go below a
0 total width when talking about *lines*, like in screen or string
length --visible.
Fixes#8277.
When cd is passed a broken symlink, this changes the error message from
"no such directory" to "broken symbolic link". This scenario probably
won't happen very often since completion won't suggest broken symlinks
but it can't hurt to give a good error.
Fish used to do this until 7ac5932. This logic used to be in
path_get_cdpath, however, that is only used for highlighting, so we
don't need error messages there. Changing cd is enough.
Reword from "rotten" to "broken" since that's what file(1) uses.
Clean-up leftovers from old "rotten" code (nomen est omen).
See #8264
This currently changes builtin realpath with the "-s" option:
builtin realpath -s ///tmp
previously would print "///tmp", now it prints "/tmp".
The only thing "allow_leading_double_slashes" does is allow *two*
slashes.
This is important for `path match`, to be introduced in #8265.
This lets us run non-fish targets (such as `fish_tests`) under a clean
test environment without running into the fish-specific payload
configuration now carried out by `test_driver.sh` which expects a
`.fish` payload that it will run under a deterministically configured
instance of fish, running in an environment initialized by
`test_env.sh`.
This should fix the problem with in-tree builds leaving detritus behind
after a `make test` when `fish_tests` would be executed without
`test_driver.sh` - it is now executed under `test_env.sh` instead.
The tmux-prompt test would sometimes fail because the first call was:
isolated-tmux capture-pane -p
this would run a capture-pane which would race with starting fish
itself; occasionally the pane would be empty since fish has not yet
drawn a prompt. Add a loop to give fish time to draw the prompt.
On macOS, the tests would often fail because calls to `pkill` would "leak"
across tests: kill processes run by other tests. This is because on macOS,
the -P argument to pkill must come before the process name. On Linux it
doesn't matter.
This improves test reliability on Mac.
For littlecheck/pexpect this just unconditionally enables color.
I have no idea what happens if you run cmake outside of a terminal
, but the worst that can happen is that *errors* have color
escapes in them.
If someone figures out how to get cmake to tell us if it's running in
a terminal, we can add a check.
This used the *logical* $PWD, but realpath would operate on the
physical $PWD if given ".", even with -s. This makes this test fail if the $PWD is
logically different from physical.
This was long overdue since the setup logic is much more complex than
the actual tests.
tmux-prompt.fish had extra logic to protect against XDG_CONFIG_HOME
with leading double double-dot. I believe this is no longer necessary
with the new test driver.
We still use our own temp dir because we want to be able to run this
independently of the test driver, This can be useful for debugging
tests. For example we can insert a "$tmux attach" command in a test,
and then run
build/fish -C 'source tests/test_functions/isolated-tmux.fish' tests/checks/tmux-bind.fish
This allows to inspect the state of the test and debug interactively.
Attaching to the terminal doesn't work when running inside littlecheck
because littlecheck consumes our output and doesn't give us a terminal.
(Maybe there's an easy way to fix that?)
On request of a team member, this patches `basic.fish` to no longer
depend on being invoked by the test driver and started up in a $PWD that
points to a clean temporary directory.
This was requested by a team member who would like for some tests to
remain invokable (in thier own $HOME) directly via littlecheck without
relying on the test driver to prep the environment.
A comment explaining the rationale is also added so this doesn't get
passed down as folklore "you need to include this for tests to run" even
though no one understands why.
Tests are now executed in a test-specific temporary directory, so test
output on failure should be reproducible/reusable as-is without needing
to have TMPDIR defined (as it only exists by default under macOS).
Instead of trying to assert that there are no zombies when the test
starts (which often fails) and to prevent conflating existing or
irrelevant zombies with the ones we are interested in checking for,
have `ps` also emit the parent process id and filter its output to
include only children of the current fish instance.
Aside from the fact that the shared state could cause problems, tests
were randomly assuming it would be created where that wasn't the case.
In particular, `redirect.fish` and `basic.fish` were failing on only
macOS because `../test/temp` didn't exist yet - it would be created by
other tests later.
Even though we are using CMake's ctest for testing, we still define our
own `make test` target rather than use its default for many reasons:
* CMake doesn't run tests in-proc or even add each tests as an
individual node in the ninja dependency tree, instead it just bundles
all tests into a target called `test` that always just shells out to
`ctest`, so there are no build-related benefits to not doing that
ourselves.
* CMake devs insist that it is appropriate for `make test` to never
depend on `make all`, i.e. running `make test` does not require any
of the binaries to be built before testing.
* The only way to have a test depend on a binary is to add a fake test
with a name like "build_fish" that executes CMake recursively to
build the `fish` target.
* It is not possible to set top-level CTest options/settings such as
CTEST_PARALLEL_LEVEL from within the CMake configuration file.
* Circling back to the point about individual tests not being actual
Makefile targets, CMake does not offer any way to execute a named
test via the `make`/`ninja`/whatever interface; the only way to
manually invoke test `foo` is to to manually run `ctest` and specify
a regex matching `foo` as an argument, e.g. `ctest -R ^foo$`... which
is really crazy.
With this patch, it is now possible to execute any single test by name,
by invoking the build directly, e.g. to run the `universal.fish` check:
`cmake --build build --target universal.fish` or
`ninja -C build universal.fish`. Unfortunately, this is not integrated
into the Makefile wrapper, so `make universal.fish` won't work (although
this can potentially be hacked around).
Fixes#8232.
Note that this needed to have expect_prompt used in the pexpect test -
we might want to add a "catchup" there so you can just ignore the
prompt counter for a bit and pick it back up later.
This disables job control inside command substitutions. Prior to this
change, a cmdsub might get its own process group. This caused it to fail
to cancel loops properly. For example:
while true ; echo (sleep 5) ; end
could not be control-C cancelled, because the signal would go to sleep,
and so the loop would continue on. The simplest way to fix this is to
match other shells and not use job control in cmdsubs.
Related is #1362
* commandline: Add --is-valid option to query whether it's syntactically complete
This means querying when the commandline is in a state that it could
be executed. Because our `execute` bind function also inserts a
newline if it isn't.
One case that's not handled right now: `execute` also expands
abbreviations, those can technically make the commandline invalid
again.
Unfortunately we have no real way to *check* without doing the
replacement.
Also since abbreviations are only available in command position when
you _execute_ them the commandline will most likely be valid.
This is enough to make transient prompts work:
```fish
function reset-transient --on-event fish_postexec
set -g TRANSIENT 0
end
function maybe_execute
if commandline --is-valid
set -g TRANSIENT 1
commandline -f repaint
else
set -g TRANSIENT 0
end
commandline -f execute
end
bind \r maybe_execute
```
and then in `fish_prompt` react to $TRANSIENT being set to 1.
