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, 33 insertions, 0 deletions

diff --git a/lua/mason-test/helpers.lua b/lua/mason-test/helpers.lua
new file mode 100644
index 00000000..57b486ea
--- /dev/null
+++ b/lua/mason-test/helpers.lua
@@ -0,0 +1,33 @@
+local InstallContext = require "mason-core.installer.context"
+local InstallContextCwd = require "mason-core.installer.context.cwd"
+local InstallContextFs = require "mason-core.installer.context.fs"
+local InstallContextSpawn = require "mason-core.installer.context.spawn"
+local InstallHandle = require "mason-core.installer.handle"
+local InstallLocation = require "mason-core.installer.location"
+local Result = require "mason-core.result"
+local registry = require "mason-registry"
+local spy = require "luassert.spy"
+
+local M = {}
+
+---@param opts? { install_opts?: PackageInstallOpts, package?: string }
+function M.create_context(opts)
+    local pkg = registry.get_package(opts and opts.package or "dummy")
+    local handle = InstallHandle.new(pkg)
+    local location = InstallLocation.new "/tmp/install-dir"
+    local context_cwd = InstallContextCwd.new(location):set(location.dir)
+    local context_spawn = InstallContextSpawn.new(context_cwd, handle, false)
+    local context_fs = InstallContextFs.new(context_cwd)
+    local context = InstallContext.new(handle, context_cwd, context_spawn, context_fs, opts and opts.install_opts or {})
+    context.spawn = setmetatable({}, {
+        __index = function(s, cmd)
+            s[cmd] = spy.new(function()
+                return Result.success { stdout = nil, stderr = nil }
+            end)
+            return s[cmd]
+        end,
+    })
+    return context
+end
+
+return M