finished with prereleases

semver.lua

@@ -19,11 +19,58 @@ end
 local function parsePrerelease(extra)
   if not present(extra) then return end
 
-  local prerelease = extra:match("-([%w-][%.%w-]+)")
+  local prerelease = extra:match("-([%w-][%.%w-]*)")
   assert(prerelease, ("The prerelease %q must start with a dash and be followed by dashes, alphanumerics or dots."):format(extra))
   return prerelease
 end
 
+-- return 0 if a == b, -1 if a < b, and 1 if a > b
+local function compare(a,b)
+  return a == b and 0 or a < b and -1 or 1
+end
+
+local function compareIds(selfId, otherId)
+  if not selfId and not otherId then return 0
+  elseif not selfId then return             1
+  elseif not otherId then return           -1
+  end
+
+  local selfNumber, otherNumber = tonumber(selfId), tonumber(otherId)
+
+  if selfNumber and otherNumber then -- numerical comparison
+    return compare(selfNumber, otherNumber)
+  elseif selfNumber then -- numericals are always smaller than alphanums
+    return -1
+  else
+    return compare(selfId, otherId) -- alphanumerical comparison
+  end
+end
+
+local function splitByDot(str)
+  local t, count = {}, 0
+  str:gsub("([^%.]+)", function(c)
+    count = count + 1
+    t[count] = c
+  end)
+  return t
+end
+
+local function smallerExtra(selfExtra, otherExtra)
+  if selfExtra == otherExtra then return false end
+
+  local selfIds, otherIds = splitByDot(selfExtra), splitByDot(otherExtra)
+  local selfLength = #selfIds
+  local comparison
+
+  for i = 1, selfLength do
+    comparison = compareIds(selfIds[i], otherIds[i])
+    if comparison ~= 0 then return comparison == -1 end
+    -- if comparison == 0, continue loop
+  end
+
+  return selfLength < #otherIds
+end
+
 local methods = {}
 
 function methods:nextMajor()
@@ -46,7 +93,9 @@ end
 function mt:__lt(other)
   return self.major < other.major or
          self.minor < other.minor or
-         self.patch < other.patch
+         self.patch < other.patch or
+         (self.prerelease and not other.prerelease) or
+         smallerExtra(self.prerelease, other.prerelease)
 end
 function mt:__pow(other)
   return self.major == other.major and

spec/semver_spec.lua

@@ -118,7 +118,30 @@ context('semver', function()
       assert_greater_than(v'0.0.2', v'0.0.1')
     end)
     describe("prereleases", function()
-      
+      test("false if exact same prerelease", function()
+        assert_false(v'1.0.0-beta' < v'1.0.0-beta')
+      end)
+      test("a prerelease version is less than the official version", function()
+        assert_less_than(v'1.0.0-rc1', v'1.0.0')
+      end)
+      test("identifiers with only digits are compared numerically", function()
+        assert_less_than(v'1.0.0-1', v'1.0.0-2')
+        assert_less_than(v'1.0.0-2', v'1.0.0-10')
+      end)
+      test("itendifiers with letters or dashes are compared lexiconumerically", function()
+        assert_less_than(v'1.0.0-alpha', v'1.0.0-beta')
+        assert_less_than(v'1.0.0-alpha-10', v'1.0.0-alpha-2')
+      end)
+      test("numerical ids always have less priority than lexiconumericals", function()
+        assert_less_than(v'1.0.0-1', v'1.0.0-alpha')
+        assert_less_than(v'1.0.0-2', v'1.0.0-1asdf')
+      end)
+      test("identifiers can be separated by colons; they must be compared individually", function()
+        assert_less_than(v'1.0.0-alpha',   v'1.0.0-alpha.1')
+        assert_less_than(v'1.0.0-alpha.1', v'1.0.0-beta.2')
+        assert_less_than(v'1.0.0-beta.2',  v'1.0.0-beta.11')
+        assert_less_than(v'1.0.0-beta.11', v'1.0.0-rc.1')
+      end)
     end)
   end)