The "principal" environment stack was the one that was associated with the
"principal" parser and would dispatch changes like to TZ, etc.
This was always very suspicious, as a global; now we can remove it.
This doesn't pull its weight. Block size is not a particularly big
problem,
and this both complicates the code a bit and would arbitrarily cause issues
if a fish script exceeded 65k lines.
This reverts commit edd6533a14.
This doesn't have any effect on the size of the struct (due to alignment
requirements and padding) but reduces the complexity by turning
Block::wants_pop_env into an emergent property dependent on the type rather than
something we have to manually manage.
We only increment it and check if it's non-zero, we never decrement or check the
actual count. As such, change it to a bool and bring the size of `Block` down
from 32 to 24 bytes.
We almost never access any of this and having it stored directly in the `Block`
struct increases its size (reducing how many we can fit in L1 and L2, and
increasing memory copy traffic).
Gets rid of BlockData::None so we can avoid allocating a Box at all when we have
no data (at the cost of yet-another-wrapper-type), which is the usual case.
This has a few advantages,
* We now statically assert that all fields used by a particular block type are
correctly initialized (i.e. you can't assign the function name but forget to
assign its arguments),
* Conversely, we can match directly on `BlockData` and be guaranteed that the
fields we want to access are initialized and present,
* We reduce the number of assertions, effectively "unwrapping" only once based
off the block type instead of each time we try to access a conditional field,
* We reduce the size of the `Block` struct by coalescing fields that cannot
co-exist, bringing it down from 104 bytes to 88 bytes.
It would be nice to make all of `Block` itself an enum, but it currently
requires `Copy` and we take advantage of that to copy it around everywhere.
Putting these fields directly in `Block` directly would mean a lot more memory
traffic just checking block types.
There's no need for two separate block types when one is merely a variant of the
other. This may have been required under C++ but thanks to sum types (rust's
enums) we don't need to do that any more.
`Parser` is a single-threaded `!Send`, `!Sync` type and does not need to use
`Arc` for anything. We were using it because that's all we had for the parser's
`EnvStack`, but though that is *technically* protected internally by a mutex
(shared with global EnvStack), there's nothing to say that other parsers with a
narrower scope/lifetime on other threads will be necessarily using the same
backing mutex.
We can safely marshal the existing `Arc<EnvStack>` we get from
`environment::principal()` into an `Rc<EnvStack>` since the underlying reference
is always valid. To prove this point, we could have PRINCIPAL_STACK be a static
`EnvStack` and have `environment::principal()` use `Arc::from_raw()` to turn
that into an `Arc<EnvStack>`, but there's no need to factorize this process.
By inverting the order of storage, we can use an `OnceCell`/`unsync::Lazy`
inside the Send/Sync `MainThread<T>` and remove the need for a lock altogether.
This allows running `set` without triggering any event handlers.
That is useful, for example, if you want to set a variable in an event
handler for that variable - we could do it, for example, in the
fish_user_path or fish_key_bindings handlers.
This is something the `block` builtin was supposed to be for, but it
never really worked because it only allows suppressing the event for
the duration, they would fire later. See #9030.
Because it is possible to abuse this, we only have a long-option so
that people see what is up.
[w]open_dir does not pass O_CREAT, so the mode argument to open is never used.
also, O_CREAT | O_DIRECTORY could not be used (portably) to create a directory.
(on POSIX does not specify what should happen, on Linux it is EINVAL.)
Remove the last non scoped place where we disable protocols (just before
exec(1)); it's not necessary with the current approach because we always
disable inside eval.
There is an edge case where we don't:
fish -ic "exec bash"
leaving bash with CSI u enabled. Disable that also in -ic mode where we
don't have a reader.
In future we should use the same approach for restore_term_mode() but I'm
not sure which one is better.
This is resistant to misuse by including O_DIRECTORY in the open flags and it is
a separate function from {w,}open_cloexec() in preparation for making that one
return a `File` instead of an `OwnedFd`.
