feat: deprecation warnings

lua/pl/utils.lua

@@ -557,6 +557,7 @@ local function _string_lambda(f)
     end
 end
 
+
 --- an anonymous function as a string. This string is either of the form
 -- '|args| expression' or is a function of one argument, '_'
 -- @param lf function as a string
@@ -587,6 +588,7 @@ function utils.bind1 (fn,p)
     return function(...) return fn(p,...) end
 end
 
+
 --- bind the second argument of the function to a value.
 -- @param fn a function of at least two values (may be an operator string)
 -- @param p a value
@@ -605,6 +607,78 @@ function utils.bind2 (fn,p)
     return function(x,...) return fn(x,p,...) end
 end
 
+
+
+
+--- Deprecation
+-- @section deprecation
+
+
+--- A deprecation warning function, to be overridden.
+-- An application can override this function to support proper output of
+-- deprecation warnings. The warnings can be generated from libraries or
+-- functions by calling `utils.raise_deprecation`. By default this function
+-- doesn't do anything.
+--
+-- Note: only applications should override this function, libraries should not.
+-- @string msg the message to display/log
+-- @string trace the traceback from where the deprecated element was invoked
+-- @usage
+-- function utils.deprecation_warning(msg, trace)
+--   io.stderr:write(msg .. "\n" .. trace .."\n")
+-- end
+function utils.deprecation_warning(msg, trace)
+  -- this does nothing by default
+end
+
+
+--- raises a deprecation warning.
+-- For options see the usage example below.
+--
+-- Note: the `opts.version_deprecated` field is the last version in which
+-- a feature or option was NOT YET deprecated! Because when writing the code it
+-- is quite often not known in what version the code will land. But the last
+-- released version is usually known.
+-- @param opts options table
+-- @see utils.deprecation_warning
+-- @usage
+-- function stringx.islower(str)
+--   deprecation_warning {
+--     source = "Penlight " .. utils._VERSION,                  -- optional
+--     message = "function 'islower' was renamed to 'is_lower'" -- required
+--     version_removed = "2.0.0",                               -- optional
+--     version_deprecated = "1.2.3",                            -- optional
+--   }
+--   return stringx.is_lower(str)
+-- end
+-- -- output: "[Penlight 1.9.2] function 'islower' was renamed to 'is_lower' (deprecated after 1.2.3, scheduled for removal in 2.0.0)"
+function utils.raise_deprecation(opts)
+  utils.assert_arg(1, opts, "table")
+  if type(opts.message) ~= "string" then
+    error("field 'message' of the options table must be a string", 2)
+  end
+  local trace = debug.traceback("", 2):match("[\n%s]*(.-)$")
+  local msg
+  if opts.version_deprecated and opts.version_removed then
+    msg = (" (deprecated after %s, scheduled for removal in %s)"):format(
+      tostring(opts.version_deprecated), tostring(opts.version_removed))
+  elseif opts.version_deprecated then
+    msg = (" (deprecated after %s)"):format(tostring(opts.version_deprecated))
+  elseif opts.version_removed then
+    msg = (" (scheduled for removal in %s)"):format(tostring(opts.version_removed))
+  else
+    msg = ""
+  end
+
+  msg = opts.message .. msg
+
+  if opts.source then
+    msg = "[" .. opts.source .."] " .. msg
+  end
+
+  utils.deprecation_warning(msg, trace)
+end
+
 return utils
 
 

spec/utils-deprecate_spec.lua

@@ -0,0 +1,102 @@
+local utils = require("pl.utils")
+
+describe("pl.utils", function ()
+
+  local old_fn, last_msg, last_trace
+
+  before_each(function()
+    old_fn = utils.deprecation_warning
+    last_msg = nil
+    last_trace = nil
+    utils.deprecation_warning = function(msg, trace)
+      last_msg = msg
+      last_trace = trace
+    end
+  end)
+
+
+  after_each(function()
+    utils.deprecation_warning = old_fn
+  end)
+
+
+
+  describe("raise_deprecation", function ()
+
+    it("requires the opts table", function()
+      assert.has.error(function() utils.raise_deprecation(nil) end,
+                       "argument 1 expected a 'table', got a 'nil'")
+    end)
+
+
+    it("requires the opts.message field", function()
+      assert.has.error(function() utils.raise_deprecation({}) end,
+                       "field 'message' of the options table must be a string")
+    end)
+
+
+    it("should output the message", function ()
+      utils.raise_deprecation {
+        message = "hello world"
+      }
+      assert.equal("hello world", last_msg)
+    end)
+
+
+    it("should output the deprecated version", function ()
+      utils.raise_deprecation {
+        message = "hello world",
+        version_deprecated = "2.0.0",
+      }
+      assert.equal("hello world (deprecated after 2.0.0)", last_msg)
+    end)
+
+
+    it("should output the removal version", function ()
+      utils.raise_deprecation {
+        message = "hello world",
+        version_removed = "3.0.0",
+      }
+      assert.equal("hello world (scheduled for removal in 3.0.0)", last_msg)
+    end)
+
+
+    it("should output the deprecated and removal versions", function ()
+      utils.raise_deprecation {
+        message = "hello world",
+        version_deprecated = "2.0.0",
+        version_removed = "3.0.0",
+      }
+      assert.equal("hello world (deprecated after 2.0.0, scheduled for removal in 3.0.0)", last_msg)
+    end)
+
+
+    it("should output the application/module name", function ()
+      utils.raise_deprecation {
+        source = "MyApp 1.2.3",
+        message = "hello world",
+        version_deprecated = "2.0.0",
+        version_removed = "3.0.0",
+      }
+      assert.equal("[MyApp 1.2.3] hello world (deprecated after 2.0.0, scheduled for removal in 3.0.0)", last_msg)
+    end)
+
+
+    it("should add a stracktrace", function ()
+      local function my_function_name()
+        utils.raise_deprecation {
+          source = "MyApp 1.2.3",
+          message = "hello world",
+          version_deprecated = "2.0.0",
+          version_removed = "3.0.0",
+        }
+      end
+      my_function_name()
+
+      assert.Not.match("raise_deprecation", last_trace)
+      assert.match("my_function_name", last_trace)
+    end)
+
+  end)
+
+end)