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, 36 insertions, 29 deletions

diff --git a/tests/mason-core/installer/handle_spec.lua b/tests/mason-core/installer/handle_spec.lua
index c301b28b..66a9a5c4 100644
--- a/tests/mason-core/installer/handle_spec.lua
+++ b/tests/mason-core/installer/handle_spec.lua
@@ -4,6 +4,16 @@ local spy = require "luassert.spy"
 local stub = require "luassert.stub"
 
 describe("installer handle", function()
+    local snapshot
+
+    before_each(function()
+        snapshot = assert.snapshot()
+    end)
+
+    after_each(function()
+        snapshot:revert()
+    end)
+
     it("should register spawn handle", function()
         local handle = InstallHandle.new(mock.new {})
         local spawn_handle_change_handler = spy.new()
@@ -72,36 +82,33 @@ describe("installer handle", function()
         assert.spy(kill_handler).was_called_with(9)
     end)
 
-    it(
-        "should terminate handle",
-        async_test(function()
-            local process = require "mason-core.process"
-            stub(process, "kill")
-            local uv_handle1 = {}
-            local uv_handle2 = {}
-            local handle = InstallHandle.new(mock.new {})
-            local kill_handler = spy.new()
-            local terminate_handler = spy.new()
-            local closed_handler = spy.new()
+    it("should terminate handle", function()
+        local process = require "mason-core.process"
+        stub(process, "kill")
+        local uv_handle1 = {}
+        local uv_handle2 = {}
+        local handle = InstallHandle.new(mock.new {})
+        local kill_handler = spy.new()
+        local terminate_handler = spy.new()
+        local closed_handler = spy.new()
 
-            handle:once("kill", kill_handler)
-            handle:once("terminate", terminate_handler)
-            handle:once("closed", closed_handler)
-            handle.state = "ACTIVE"
-            handle.spawn_handles = { { uv_handle = uv_handle2 }, { uv_handle = uv_handle2 } }
-            handle:terminate()
+        handle:once("kill", kill_handler)
+        handle:once("terminate", terminate_handler)
+        handle:once("closed", closed_handler)
+        handle.state = "ACTIVE"
+        handle.spawn_handles = { { uv_handle = uv_handle2 }, { uv_handle = uv_handle2 } }
+        handle:terminate()
 
-            assert.spy(process.kill).was_called(2)
-            assert.spy(process.kill).was_called_with(uv_handle1, 15)
-            assert.spy(process.kill).was_called_with(uv_handle2, 15)
-            assert.spy(kill_handler).was_called(1)
-            assert.spy(kill_handler).was_called_with(15)
-            assert.spy(terminate_handler).was_called(1)
-            assert.is_true(handle.is_terminated)
-            assert.wait_for(function()
-                assert.is_true(handle:is_closed())
-                assert.spy(closed_handler).was_called(1)
-            end)
+        assert.spy(process.kill).was_called(2)
+        assert.spy(process.kill).was_called_with(uv_handle1, 15)
+        assert.spy(process.kill).was_called_with(uv_handle2, 15)
+        assert.spy(kill_handler).was_called(1)
+        assert.spy(kill_handler).was_called_with(15)
+        assert.spy(terminate_handler).was_called(1)
+        assert.is_true(handle.is_terminated)
+        assert.wait(function()
+            assert.is_true(handle:is_closed())
+            assert.spy(closed_handler).was_called(1)
         end)
-    )
+    end)
 end)