feat(compat) add a 5.4 compatible "warn" function

also updates the derpecation warnings to use the warn function

CHANGELOG.md

@@ -12,6 +12,8 @@ see [CONTRIBUTING.md](CONTRIBUTING.md#release-instructions-for-a-new-version) fo
    [#360](https://github.com/lunarmodules/Penlight/pull/360)
  - feat: `permute.list_table` generate table with different sets of values
    [#360](https://github.com/lunarmodules/Penlight/pull/360)
+ - feat: Lua 5.4 'warn' compatibility function
+   [#366](https://github.com/lunarmodules/Penlight/pull/366)
  - feat: deprecation functionality `utils.raise_deprecation`
    [#361](https://github.com/lunarmodules/Penlight/pull/361)
  - fix: `dir.rmtree` failed to remove symlinks to directories

lua/pl/compat.lua

@@ -218,4 +218,33 @@ if not package.searchpath then
     end
 end
 
+--- Global exported functions (for Lua < 5.4)
+-- @section lua54
+
+--- raise a warning message.
+-- This functions mimics the `warn` function added in Lua 5.4.
+-- @function warn
+-- @param ... any arguments
+if not warn then  -- luacheck: ignore
+    local enabled = false
+    function warn(arg1, ...)  -- luacheck: ignore
+        if type(arg1) == "string" and arg1:sub(1, 1) == "@" then
+            -- control message
+            if arg1 == "@on" then
+                enabled = true
+                return
+            end
+            if arg1 == "@off" then
+                enabled = false
+                return
+            end
+            return -- ignore unknown control messages
+        end
+        if enabled then
+          io.stderr:write("Lua warning: ", arg1, ...)
+          io.stderr:write("\n")
+        end
+    end
+end
+
 return compat

lua/pl/permute.lua

@@ -166,11 +166,11 @@ end
 -- @param ...
 -- @see permute.order_iter
 function permute.iter(...)
-  utils.deprecation_warning {
+  utils.raise_deprecation {
     source = "Penlight " .. utils._VERSION,
     message = "function 'iter' was renamed to 'order_iter'",
     version_removed = "2.0.0",
-    version_deprecated = "1.9.2",
+    deprecated_after = "1.9.2",
   }
 
   return permute.order_iter(...)
@@ -180,11 +180,11 @@ end
 -- @param ...
 -- @see permute.order_iter
 function permute.table(...)
-  utils.deprecation_warning {
+  utils.raise_deprecation {
     source = "Penlight " .. utils._VERSION,
     message = "function 'table' was renamed to 'order_table'",
     version_removed = "2.0.0",
-    version_deprecated = "1.9.2",
+    deprecated_after = "1.9.2",
   }
 
   return permute.order_table(...)

lua/pl/utils.lua

@@ -613,72 +613,96 @@ end
 --- Deprecation
 -- @section deprecation
 
+do
+  -- the default implementation
+  local deprecation_func = function(msg, trace)
+    warn(msg, "\n", trace)  -- luacheck: ignore
+  end
 
---- 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
+  --- Sets a deprecation warning function.
+  -- 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`. The default function
+  -- will write to the 'warn' system (introduced in Lua 5.4, or the compatibility
+  -- function from the `compat` module for earlier versions).
+  --
+  -- Note: only applications should set/change this function, libraries should not.
+  -- @function a callback with signature: `function(msg, trace)` both arguments are strings.
+  -- @see utils.raise_deprecation
+  -- @usage
+  -- -- write to the Nginx logs with OpenResty
+  -- utils.set_deprecation_func(function(msg, trace)
+  --   ngx.log(ngx.WARN, msg, " ", trace)
+  -- end)
+  --
+  -- -- disable deprecation warnings
+  -- utils.deprecation_warning()
+  function utils.set_deprecation_func(func)
+    if func == nil then
+      deprecation_func = function() end
+    else
+      utils.assert_arg(1, func, "function")
+      deprecation_func = func
+    end
+  end
 
+  --- raises a deprecation warning.
+  -- For options see the usage example below.
+  --
+  -- Note: the `opts.deprecated_after` 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.set_deprecation_func
+  -- @usage
+  -- warn("@on")   -- enable Lua warnings, they are usually off by default
+  --
+  -- function stringx.islower(str)
+  --   raise_deprecation {
+  --     source = "Penlight " .. utils._VERSION,                  -- optional
+  --     message = "function 'islower' was renamed to 'is_lower'" -- required
+  --     version_removed = "2.0.0",                               -- optional
+  --     deprecated_after = "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.deprecated_after and opts.version_removed then
+      msg = (" (deprecated after %s, scheduled for removal in %s)"):format(
+        tostring(opts.deprecated_after), tostring(opts.version_removed))
+    elseif opts.deprecated_after then
+      msg = (" (deprecated after %s)"):format(tostring(opts.deprecated_after))
+    elseif opts.version_removed then
+      msg = (" (scheduled for removal in %s)"):format(tostring(opts.version_removed))
+    else
+      msg = ""
+    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
 
-  msg = opts.message .. msg
+    if opts.source then
+      msg = "[" .. opts.source .."] " .. msg
+    else
+      if msg:sub(1,1) == "@" then
+        -- in Lua 5.4 "@" prefixed messages are control messages to the warn system
+        error("message cannot start with '@'", 2)
+      end
+    end
 
-  if opts.source then
-    msg = "[" .. opts.source .."] " .. msg
+    deprecation_func(msg, trace)
   end
 
-  utils.deprecation_warning(msg, trace)
 end
 
+
 return utils
 
 

spec/utils-deprecate_spec.lua

@@ -5,13 +5,13 @@ describe("pl.utils", function ()
   local old_fn, last_msg, last_trace
 
   before_each(function()
-    old_fn = utils.deprecation_warning
+    old_fn = function() end
     last_msg = nil
     last_trace = nil
-    utils.deprecation_warning = function(msg, trace)
+    utils.set_deprecation_func(function(msg, trace)
       last_msg = msg
       last_trace = trace
-    end
+    end)
   end)
 
 
@@ -21,6 +21,32 @@ describe("pl.utils", function ()
 
 
 
+  describe("set_deprecation_func", function ()
+
+    it("accepts nil as callback", function()
+      assert.has.no.error(function()
+        utils.set_deprecation_func()
+      end)
+    end)
+
+
+    it("accepts function as callback", function()
+      assert.has.no.error(function()
+        utils.set_deprecation_func(function() end)
+      end)
+    end)
+
+
+    it("fails on non-functions", function()
+      assert.has.error(function()
+        utils.set_deprecation_func("not a function")
+      end, "argument 1 expected a 'function', got a 'string'")
+    end)
+
+  end)
+
+
+
   describe("raise_deprecation", function ()
 
     it("requires the opts table", function()
@@ -46,7 +72,7 @@ describe("pl.utils", function ()
     it("should output the deprecated version", function ()
       utils.raise_deprecation {
         message = "hello world",
-        version_deprecated = "2.0.0",
+        deprecated_after = "2.0.0",
       }
       assert.equal("hello world (deprecated after 2.0.0)", last_msg)
     end)
@@ -64,7 +90,7 @@ describe("pl.utils", function ()
     it("should output the deprecated and removal versions", function ()
       utils.raise_deprecation {
         message = "hello world",
-        version_deprecated = "2.0.0",
+        deprecated_after = "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)
@@ -75,7 +101,7 @@ describe("pl.utils", function ()
       utils.raise_deprecation {
         source = "MyApp 1.2.3",
         message = "hello world",
-        version_deprecated = "2.0.0",
+        deprecated_after = "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)
@@ -87,7 +113,7 @@ describe("pl.utils", function ()
         utils.raise_deprecation {
           source = "MyApp 1.2.3",
           message = "hello world",
-          version_deprecated = "2.0.0",
+          deprecated_after = "2.0.0",
           version_removed = "3.0.0",
         }
       end

tests/test-strict.lua

@@ -1,3 +1,4 @@
+warn = warn or true-- declare 'warn' as a global, to be added in compat module
 local strict = require 'pl.strict'
 local test = require 'pl.test'
 local app = require 'pl.app'