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, 102 insertions, 105 deletions

diff --git a/tests/mason-core/fetch_spec.lua b/tests/mason-core/fetch_spec.lua
index 107b6417..5a890318 100644
--- a/tests/mason-core/fetch_spec.lua
+++ b/tests/mason-core/fetch_spec.lua
@@ -6,118 +6,115 @@ local stub = require "luassert.stub"
 local version = require "mason.version"
 
 describe("fetch", function()
-    it(
-        "should exhaust all candidates",
-        async_test(function()
-            stub(spawn, "wget")
-            stub(spawn, "curl")
-            spawn.wget.returns(Result.failure "wget failure")
-            spawn.curl.returns(Result.failure "curl failure")
+    local snapshot
 
-            local result = fetch("https://api.github.com", {
-                headers = { ["X-Custom-Header"] = "here" },
-            })
-            assert.is_true(result:is_failure())
-            assert.spy(spawn.wget).was_called(1)
-            assert.spy(spawn.curl).was_called(1)
-            assert.spy(spawn.wget).was_called_with {
-                {
-                    ("--header=User-Agent: mason.nvim %s (+https://github.com/williamboman/mason.nvim)"):format(
-                        version.VERSION
-                    ),
-                    "--header=X-Custom-Header: here",
-                },
-                "-nv",
-                "-o",
-                "/dev/null",
-                "-O",
-                "-",
-                "--timeout=30",
-                "--method=GET",
-                vim.NIL, -- body-data
-                "https://api.github.com",
-            }
+    before_each(function()
+        snapshot = assert.snapshot()
+    end)
 
-            assert.spy(spawn.curl).was_called_with(match.tbl_containing {
-                match.same {
-                    {
-                        "-H",
-                        ("User-Agent: mason.nvim %s (+https://github.com/williamboman/mason.nvim)"):format(
-                            version.VERSION
-                        ),
-                    },
-                    {
-                        "-H",
-                        "X-Custom-Header: here",
-                    },
-                },
-                "-fsSL",
-                match.same { "-X", "GET" },
-                vim.NIL, -- data
-                vim.NIL, -- out file
-                match.same { "--connect-timeout", 30 },
-                "https://api.github.com",
-                on_spawn = match.is_function(),
-            })
-        end)
-    )
+    after_each(function()
+        snapshot:revert()
+    end)
 
-    it(
-        "should return stdout",
-        async_test(function()
-            stub(spawn, "wget")
-            spawn.wget.returns(Result.success {
-                stdout = [[{"data": "here"}]],
-            })
-            local result = fetch "https://api.github.com/data"
-            assert.is_true(result:is_success())
-            assert.equals([[{"data": "here"}]], result:get_or_throw())
-        end)
-    )
+    it("should exhaust all candidates", function()
+        stub(spawn, "wget")
+        stub(spawn, "curl")
+        spawn.wget.returns(Result.failure "wget failure")
+        spawn.curl.returns(Result.failure "curl failure")
 
-    it(
-        "should respect out_file opt",
-        async_test(function()
-            stub(spawn, "wget")
-            stub(spawn, "curl")
-            spawn.wget.returns(Result.failure "wget failure")
-            spawn.curl.returns(Result.failure "curl failure")
-            fetch("https://api.github.com/data", { out_file = "/test.json" })
+        local result = fetch("https://api.github.com", {
+            headers = { ["X-Custom-Header"] = "here" },
+        })
+        assert.is_true(result:is_failure())
+        assert.spy(spawn.wget).was_called(1)
+        assert.spy(spawn.curl).was_called(1)
+        assert.spy(spawn.wget).was_called_with {
+            {
+                ("--header=User-Agent: mason.nvim %s (+https://github.com/williamboman/mason.nvim)"):format(
+                    version.VERSION
+                ),
+                "--header=X-Custom-Header: here",
+            },
+            "-nv",
+            "-o",
+            "/dev/null",
+            "-O",
+            "-",
+            "--timeout=30",
+            "--method=GET",
+            vim.NIL, -- body-data
+            "https://api.github.com",
+        }
 
-            assert.spy(spawn.wget).was_called_with {
+        assert.spy(spawn.curl).was_called_with(match.tbl_containing {
+            match.same {
+                {
+                    "-H",
+                    ("User-Agent: mason.nvim %s (+https://github.com/williamboman/mason.nvim)"):format(version.VERSION),
+                },
                 {
-                    ("--header=User-Agent: mason.nvim %s (+https://github.com/williamboman/mason.nvim)"):format(
-                        version.VERSION
-                    ),
+                    "-H",
+                    "X-Custom-Header: here",
                 },
-                "-nv",
-                "-o",
-                "/dev/null",
-                "-O",
-                "/test.json",
-                "--timeout=30",
-                "--method=GET",
-                vim.NIL, -- body-data
-                "https://api.github.com/data",
-            }
+            },
+            "-fsSL",
+            match.same { "-X", "GET" },
+            vim.NIL, -- data
+            vim.NIL, -- out file
+            match.same { "--connect-timeout", 30 },
+            "https://api.github.com",
+            on_spawn = match.is_function(),
+        })
+    end)
 
-            assert.spy(spawn.curl).was_called_with(match.tbl_containing {
-                match.same {
-                    {
-                        "-H",
-                        ("User-Agent: mason.nvim %s (+https://github.com/williamboman/mason.nvim)"):format(
-                            version.VERSION
-                        ),
-                    },
+    it("should return stdout", function()
+        stub(spawn, "curl")
+        spawn.curl.returns(Result.success {
+            stdout = [[{"data": "here"}]],
+        })
+        local result = fetch "https://api.github.com/data"
+        assert.is_true(result:is_success())
+        assert.equals([[{"data": "here"}]], result:get_or_throw())
+    end)
+
+    it("should respect out_file opt", function()
+        stub(spawn, "wget")
+        stub(spawn, "curl")
+        spawn.wget.returns(Result.failure "wget failure")
+        spawn.curl.returns(Result.failure "curl failure")
+        fetch("https://api.github.com/data", { out_file = "/test.json" })
+
+        assert.spy(spawn.wget).was_called_with {
+            {
+                ("--header=User-Agent: mason.nvim %s (+https://github.com/williamboman/mason.nvim)"):format(
+                    version.VERSION
+                ),
+            },
+            "-nv",
+            "-o",
+            "/dev/null",
+            "-O",
+            "/test.json",
+            "--timeout=30",
+            "--method=GET",
+            vim.NIL, -- body-data
+            "https://api.github.com/data",
+        }
+
+        assert.spy(spawn.curl).was_called_with(match.tbl_containing {
+            match.same {
+                {
+                    "-H",
+                    ("User-Agent: mason.nvim %s (+https://github.com/williamboman/mason.nvim)"):format(version.VERSION),
                 },
-                "-fsSL",
-                match.same { "-X", "GET" },
-                vim.NIL, -- data
-                match.same { "-o", "/test.json" },
-                match.same { "--connect-timeout", 30 },
-                "https://api.github.com/data",
-                on_spawn = match.is_function(),
-            })
-        end)
-    )
+            },
+            "-fsSL",
+            match.same { "-X", "GET" },
+            vim.NIL, -- data
+            match.same { "-o", "/test.json" },
+            match.same { "--connect-timeout", 30 },
+            "https://api.github.com/data",
+            on_spawn = match.is_function(),
+        })
+    end)
 end)