refactor!: refactor installer internals and add new Package class methods (#1523)

This contains the following changes:
1) `Package:install()` now accepts a second, optional, callback argument which is called when installation finishes
   (successfully or not).
2) Adds a `Package:is_installing()` method.

This contains the following breaking changes:
1) `Package:install()` will now error when called while an installation is already ongoing. Use the new
   `Package:is_installing()` method to check whether an installation is already running.

This also refactors large portions of the tests by removing test globals, removing async_test, and adding the
`mason-test` Lua module instead. Test helpers via globals are problematic to work with due to not being detected through
tools like the Lua language server without additional configuration. This has been replaced with a Lua module
`mason-test`. `async_test` has also been removed in favour of explicitly making use of the `mason-core.async` API. These
changes stands for a significant portion of the diff.

1 files changed, 48 insertions, 0 deletions

diff --git a/lua/mason-core/installer/context/cwd.lua b/lua/mason-core/installer/context/cwd.lua
new file mode 100644
index 00000000..4f645fbb
--- /dev/null
+++ b/lua/mason-core/installer/context/cwd.lua
@@ -0,0 +1,48 @@
+local Result = require "mason-core.result"
+local fs = require "mason-core.fs"
+local path = require "mason-core.path"
+
+---@class InstallContextCwd
+---@field private location InstallLocation Defines the upper boundary for which paths are allowed as cwd.
+---@field private cwd string?
+local InstallContextCwd = {}
+InstallContextCwd.__index = InstallContextCwd
+
+---@param location InstallLocation
+function InstallContextCwd.new(location)
+    assert(location, "location not provided")
+    return setmetatable({
+        location = location,
+        cwd = nil,
+    }, InstallContextCwd)
+end
+
+---@param handle InstallHandle
+function InstallContextCwd:initialize(handle)
+    return Result.try(function(try)
+        local staging_dir = self.location:staging(handle.package.name)
+        if fs.async.dir_exists(staging_dir) then
+            try(Result.pcall(fs.async.rmrf, staging_dir))
+        end
+        try(Result.pcall(fs.async.mkdirp, staging_dir))
+        self:set(staging_dir)
+    end)
+end
+
+function InstallContextCwd:get()
+    assert(self.cwd ~= nil, "Tried to access cwd before it was set.")
+    return self.cwd
+end
+
+---@param new_abs_cwd string
+function InstallContextCwd:set(new_abs_cwd)
+    assert(type(new_abs_cwd) == "string", "new_cwd is not a string")
+    assert(
+        path.is_subdirectory(self.location:get_dir(), new_abs_cwd),
+        ("%q is not a subdirectory of %q"):format(new_abs_cwd, self.location)
+    )
+    self.cwd = new_abs_cwd
+    return self
+end
+
+return InstallContextCwd