The original intent of this patch was to remove more unwraps to reduce
panics. I then lost a ton of time to the fact that the playground isn't
in a temp directory (because of permissions issues on Windows).
This commit improves the test facilities to:
- use a tempdir for the playground
- change the playground API so you instantiate it with a block that
encloses the lifetime of the tempdir
- the block is called with a `dirs` argument that has `dirs.test()` and
other important directories that we were computing by hand all the time
- the block is also called with a `playground` argument that you can use
to construct files (it's the same `Playground` as before)
- change the nu! and nu_error! macros to produce output instead of
taking a variable binding
- change the nu! and nu_error! macros to do the cwd() transformation
internally
- change the nu! and nu_error! macros to take varargs at the end that
get interpolated into the running command
I didn't manage to finish porting all of the tests, so a bunch of tests
are currently commented out. That will need to change before we land
this patch.
This ended up being a bit of a yak shave. The basic idea in this commit is to
expand `~` in paths, but only in paths.
The way this is accomplished is by doing the expansion inside of the code that
parses literal syntax for `SyntaxType::Path`.
As a quick refresher: every command is entitled to expand its arguments in a
custom way. While this could in theory be used for general-purpose macros,
today the expansion facility is limited to syntactic hints.
For example, the syntax `where cpu > 0` expands under the hood to
`where { $it.cpu > 0 }`. This happens because the first argument to `where`
is defined as a `SyntaxType::Block`, and the parser coerces binary expressions
whose left-hand-side looks like a member into a block when the command is
expecting one.
This is mildly more magical than what most programming languages would do,
but we believe that it makes sense to allow commands to fine-tune the syntax
because of the domain nushell is in (command-line shells).
The syntactic expansions supported by this facility are relatively limited.
For example, we don't allow `$it` to become a bare word, simply because the
command asks for a string in the relevant position. That would quickly
become more confusing than it's worth.
This PR adds a new `SyntaxType` rule: `SyntaxType::Path`. When a command
declares a parameter as a `SyntaxType::Path`, string literals and bare
words passed as an argument to that parameter are processed using the
path expansion rules. Right now, that only means that `~` is expanded into
the home directory, but additional rules are possible in the future.
By restricting this expansion to a syntactic expansion when passed as an
argument to a command expecting a path, we avoid making `~` a generally
reserved character. This will also allow us to give good tab completion
for paths with `~` characters in them when a command is expecting a path.
In order to accomplish the above, this commit changes the parsing functions
to take a `Context` instead of just a `CommandRegistry`. From the perspective
of macro expansion, you can think of the `CommandRegistry` as a dictionary
of in-scope macros, and the `Context` as the compile-time state used in
expansion. This could gain additional functionality over time as we find
more uses for the expansion system.
