feat(utils) enum to accept hash tables as well

3 files changed, 199 insertions, 39 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 70fd196..b3385f0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,8 +7,13 @@ deprecation policy.
 see [CONTRIBUTING.md](CONTRIBUTING.md#release-instructions-for-a-new-version) for release instructions
 
 ## 1.13.0 (unreleased)
+<<<<<<< HEAD
  - fix: `compat.warn` raised write guard warning in OpenResty
    [#414](https://github.com/lunarmodules/Penlight/pull/414)
+=======
+ - feat: `utils.enum` now accepts hash tables, to enable better error handling
+
+>>>>>>> b38c390 (feat(utils) enum to accept hash tables as well)
 
 ## 1.12.0 (2022-Jan-10)
  - deprecate: module `pl.text` the contents have moved to `pl.stringx` (removal later)
diff --git a/lua/pl/utils.lua b/lua/pl/utils.lua
index 1cb8a64..d56a6ef 100644
--- a/lua/pl/utils.lua
+++ b/lua/pl/utils.lua
@@ -249,17 +249,20 @@ function utils.assert_arg (n,val,tp,verify,msg,lev)
     return val
 end
 
---- creates an Enum table.
+--- creates an Enum or constants lookup table for improved error handling.
 -- This helps prevent magic strings in code by throwing errors for accessing
--- non-existing values.
+-- non-existing values, and/or converting strings/identifiers to other values.
 --
--- Calling on the object does the same, but returns a soft error; `nil + err`.
+-- Calling on the object does the same, but returns a soft error; `nil + err`, if
+-- the call is succesful (the key exists), it will return the value.
 --
--- The values are equal to the keys. The enum object is
--- read-only.
--- @param ... strings that make up the enumeration.
--- @return Enum object
--- @usage -- accessing at runtime
+-- When calling with varargs or an array the values will be equal to the keys.
+-- The enum object is read-only.
+-- @tparam table|vararg ... the input for the Enum. If varargs or an array then the
+-- values in the Enum will be equal to the names (must be strings), if a hash-table
+-- then values remain (any type), and the keys must be strings.
+-- @return Enum object (read-only table/object)
+-- @usage -- Enum access at runtime
 -- local obj = {}
 -- obj.MOVEMENT = utils.enum("FORWARD", "REVERSE", "LEFT", "RIGHT")
 --
@@ -271,21 +274,83 @@ end
 --   -- "'REVERES' is not a valid value (expected one of: 'FORWARD', 'REVERSE', 'LEFT', 'RIGHT')"
 --
 -- end
--- @usage -- validating user-input
--- local parameter = "...some user provided option..."
--- local ok, err = obj.MOVEMENT(parameter) -- calling on the object
--- if not ok then
---   print("bad 'parameter', " .. err)
+-- @usage -- standardized error codes
+-- local obj = {
+--   ERR = utils.enum {
+--     NOT_FOUND = "the item was not found",
+--     OUT_OF_BOUNDS = "the index is outside the allowed range"
+--   },
+--
+--   some_method = function(self)
+--     return self.ERR.OUT_OF_BOUNDS
+--   end,
+-- }
+--
+-- local result, err = obj:some_method()
+-- if not result then
+--   if err == obj.ERR.NOT_FOUND then
+--     -- check on error code, not magic strings
+--
+--   else
+--     -- return the error description, contained in the constant
+--     return nil, "error: "..err  -- "error: the index is outside the allowed range"
+--   end
+-- end
+-- @usage -- validating/converting user-input
+-- local color = "purple"
+-- local ansi_colors = utils.enum {
+--   black     = 30,
+--   red       = 31,
+--   green     = 32,
+-- }
+-- local color_code, err = ansi_colors(color) -- calling on the object, returns the value from the enum
+-- if not color_code then
+--   print("bad 'color', " .. err)
+--   -- "bad 'color', 'purple' is not a valid value (expected one of: 'black', 'red', 'green')"
 --   os.exit(1)
 -- end
 function utils.enum(...)
-  local lst = utils.pack(...)
-  utils.assert_arg(1, lst[1], "string") -- at least 1 string
-
+  local first = select(1, ...)
   local enum = {}
-  for i, value in ipairs(lst) do
-    utils.assert_arg(i, value, "string")
-    enum[value] = value
+  local lst
+
+  if type(first) ~= "table" then
+    -- vararg with strings
+    lst = utils.pack(...)
+    for i, value in ipairs(lst) do
+      utils.assert_arg(i, value, "string")
+      enum[value] = value
+    end
+
+  else
+    -- table/array with values
+    utils.assert_arg(1, first, "table")
+    lst = {}
+    -- first add array part
+    for i, value in ipairs(first) do
+      if type(value) ~= "string" then
+        error(("expected 'string' but got '%s' at index %d"):format(type(value), i), 2)
+      end
+      lst[i] = value
+      enum[value] = value
+    end
+    -- add key-ed part
+    for key, value in pairs(first) do
+      if not lst[key] then
+        if type(key) ~= "string" then
+          error(("expected key to be 'string' but got '%s'"):format(type(key)), 2)
+        end
+          if enum[key] then
+          error(("duplicate entry in array and hash part: '%s'"):format(key), 2)
+        end
+        enum[key] = value
+        lst[#lst+1] = key
+      end
+    end
+  end
+
+  if not lst[1] then
+    error("expected at least 1 entry", 2)
   end
 
   local valid = "(expected one of: '" .. concat(lst, "', '") .. "')"
@@ -299,7 +364,7 @@ function utils.enum(...)
     __call = function(self, key)
       if type(key) == "string" then
         local v = rawget(self, key)
-        if v then
+        if v ~= nil then
           return v
         end
       end
diff --git a/spec/utils-enum_spec.lua b/spec/utils-enum_spec.lua
index 752acb9..21fde62 100644
--- a/spec/utils-enum_spec.lua
+++ b/spec/utils-enum_spec.lua
@@ -5,45 +5,130 @@ describe("pl.utils", function ()
 
     before_each(function()
       enum = require("pl.utils").enum
-      t = enum("ONE", "two", "THREE")
     end)
 
 
-    it("holds enumerated values", function()
-      assert.equal("ONE", t.ONE)
-      assert.equal("two", t.two)
-      assert.equal("THREE", t.THREE)
-    end)
+    describe("creating", function()
 
+      it("accepts a vararg", function()
+        t = enum("ONE", "two", "THREE")
+        assert.same({
+          ONE = "ONE",
+          two = "two",
+          THREE = "THREE",
+        }, t)
+      end)
 
 
-    describe("accessing", function()
+      it("vararg entries must be strings", function()
+        assert.has.error(function()
+          t = enum("hello", true, "world")
+        end, "argument 2 expected a 'string', got a 'boolean'")
+      end)
 
-      it("errors on unknown values", function()
+
+      it("vararg requires at least 1 entry", function()
         assert.has.error(function()
-          print(t.four)
-        end, "'four' is not a valid value (expected one of: 'ONE', 'two', 'THREE')")
+          t = enum()
+        end, "expected at least 1 entry")
       end)
 
 
-      it("errors on setting new keys", function()
+      it("accepts an array", function()
+        t = enum { "ONE", "two", "THREE" }
+        assert.same({
+          ONE = "ONE",
+          two = "two",
+          THREE = "THREE",
+        }, t)
+      end)
+
+
+      it("array entries must be strings", function()
         assert.has.error(function()
-          t.four = "four"
-        end, "the Enum object is read-only")
+          t = enum { "ONE", 999, "THREE" }
+        end, "expected 'string' but got 'number' at index 2")
       end)
 
 
-      it("entries must be strings", function()
+      it("array requires at least 1 entry", function()
         assert.has.error(function()
-          t = enum("hello", true, "world")
-        end, "argument 2 expected a 'string', got a 'boolean'")
+          t = enum {}
+        end, "expected at least 1 entry")
+      end)
+
+
+      it("accepts a hash-table", function()
+        t = enum {
+          FILE_NOT_FOUND = "The file was not found in the filesystem",
+          FILE_READ_ONLY = "The file is read-only",
+        }
+        assert.same({
+          FILE_NOT_FOUND = "The file was not found in the filesystem",
+          FILE_READ_ONLY = "The file is read-only",
+        }, t)
       end)
 
 
-      it("requires at least 1 entry", function()
+      it("hash-table keys must be strings", function()
         assert.has.error(function()
-          t = enum()
-        end, "argument 1 expected a 'string', got a 'nil'")
+          t = enum { [{}] = "ONE" }
+        end, "expected key to be 'string' but got 'table'")
+      end)
+
+
+      it("hash-table requires at least 1 entry", function()
+        assert.has.error(function()
+          t = enum {}
+        end, "expected at least 1 entry")
+      end)
+
+
+      it("accepts a combined array/hash-table", function()
+        t = enum {
+          "BAD_FD",
+          FILE_NOT_FOUND = "The file was not found in the filesystem",
+          FILE_READ_ONLY = "The file is read-only",
+        }
+        assert.same({
+          BAD_FD = "BAD_FD",
+          FILE_NOT_FOUND = "The file was not found in the filesystem",
+          FILE_READ_ONLY = "The file is read-only",
+        }, t)
+      end)
+
+
+      it("keys must be unique with combined array/has-table", function()
+        assert.has.error(function()
+          t = enum {
+            "FILE_NOT_FOUND",
+            FILE_NOT_FOUND = "The file was not found in the filesystem",
+          }
+          end, "duplicate entry in array and hash part: 'FILE_NOT_FOUND'")
+      end)
+
+    end)
+
+
+
+    describe("accessing", function()
+
+      before_each(function()
+        t = enum("ONE", "two", "THREE")
+      end)
+
+
+      it("errors on unknown values", function()
+        assert.has.error(function()
+          print(t.four)
+        end, "'four' is not a valid value (expected one of: 'ONE', 'two', 'THREE')")
+      end)
+
+
+      it("errors on setting new keys", function()
+        assert.has.error(function()
+          t.four = "four"
+        end, "the Enum object is read-only")
       end)
 
 
@@ -60,6 +145,11 @@ describe("pl.utils", function ()
 
     describe("calling", function()
 
+      before_each(function()
+        t = enum("ONE", "two", "THREE")
+      end)
+
+
       it("returns error on unknown values", function()
         local ok, err = t("four")
         assert.equal(err, "'four' is not a valid value (expected one of: 'ONE', 'two', 'THREE')")