compat: add vim.system fallback (#27)

lua/sg/system.lua

@@ -2,6 +2,6 @@ local async = require "plenary.async"
 
 return {
   async = async.wrap(function(a, b, c)
-    return vim.system(a, b, vim.schedule_wrap(c))
+    return require("sg.utils").system(a, b, vim.schedule_wrap(c))
   end, 3),
 }

lua/sg/utils.lua

@@ -59,4 +59,22 @@ utils.joinpath = vim.fs.joinpath or function(...)
   return (table.concat({ ... }, "/"):gsub("//+", "/"))
 end
 
+-- COMPAT(0.10.0)
+-- So far only handle stdout, no other items are handled.
+-- Probably will break on me unexpectedly. Nice
+utils.system = vim.system
+  or function(cmd, opts, on_exit)
+    local stdout = ""
+    opts.stdout_buffered = true
+    opts.on_stdout = function(_, data)
+      stdout = stdout .. table.concat(data, "")
+    end
+    opts.on_exit = function()
+      stdout = stdout .. "\n"
+      on_exit { stdout = stdout, compat = true }
+    end
+
+    vim.fn.jobstart(cmd, opts)
+  end
+
 return utils

lua/tests/async_compat_spec.lua

@@ -0,0 +1,15 @@
+require("plenary.async").tests.add_to_env()
+
+local system = require "sg.system"
+
+local eq = assert.are.same
+
+describe("compat", function()
+  describe("vim.system", function()
+    a.it("void functions can call wrapped functions", function()
+      local obj = system.async({ "echo", "hello" }, { text = true })
+      local result = obj.stdout
+      eq(result, "hello\n")
+    end)
+  end)
+end)