+ Add tests for bidi rule W2

bidi.lua

@@ -97,7 +97,13 @@ bidi.W1 = function(run, sos)
    return run
 end
 
-bidi.W2 = function(run, sos)
+local W2 = function(run, sos)
+   -- sos is the text ordering type assigned to the virtual position
+   -- before an isolating run sequence
+   assert(
+      "L" == sos or
+      "R" == sos
+   )
    for i = 1, #run do
       if "EN" == run[i].bidi_class then
          -- Search backward from each instance of a European number
@@ -105,30 +111,102 @@ bidi.W2 = function(run, sos)
          local previous_strong_bidi_class = nil
          local j = i
          repeat
+            j = j - 1
             local previous_bidi_class = run[j].bidi_class
             if (
                "L" == previous_bidi_class or  -- left-to-right
                "R" == previous_bidi_class or  -- right-to-left
                "AL" == previous_bidi_class or -- right-to-left (arabic)
-               sos == previvous_bidi_class
+               sos == previous_bidi_class
             ) then
                previous_strong_bidi_class = previous_bidi_class
             end
-            j = j - 1
          until(
             nil ~= previous_strong_bidi_class or
-            0 == j
+            1 == j
          )
          -- If an AL is found, change the type of the European number
          -- to Arabic number.
-         if "AL" == run[i].bidi_class then
+         if "AL" == previous_strong_bidi_class then
-            run[i].bidi_class = "R"
+            run[i].bidi_class = "AN"
          end
       end
    end
    return run
 end
 
+-- Test W2: AL EN → AL AN
+local test_input = {
+   { ["bidi_class"] = "AL" },
+   { ["bidi_class"] = "EN" },
+}
+local test_output = W2(test_input, "L")
+assert(
+   "AL" == test_output[1].bidi_class and
+   "AN" == test_output[2].bidi_class
+)
+
+-- Test W2: AL NI EN → AL NI AN
+local test_input = {
+   { ["bidi_class"] = "AL" },
+   { ["bidi_class"] = "NI" },
+   { ["bidi_class"] = "EN" },
+}
+local test_output = W2(test_input, "L")
+assert(
+   "AL" == test_output[1].bidi_class and
+   "NI" == test_output[2].bidi_class and
+   "AN" == test_output[3].bidi_class
+)
+
+-- Test W2: sos NI EN → sos NI EN (sos = L)
+local test_input = {
+   { ["bidi_class"] = "NI" },
+   { ["bidi_class"] = "EN" },
+}
+local test_output = W2(test_input, "L")
+assert(
+   "NI" == test_output[1].bidi_class and
+   "EN" == test_output[2].bidi_class
+)
+
+-- Test W2: sos NI EN → sos NI EN (sos = R)
+local test_input = {
+   { ["bidi_class"] = "NI" },
+   { ["bidi_class"] = "EN" },
+}
+local test_output = W2(test_input, "R")
+assert(
+   "NI" == test_output[1].bidi_class and
+   "EN" == test_output[2].bidi_class
+)
+
+-- Test W2: L NI EN → L NI AN
+local test_input = {
+   { ["bidi_class"] = "L" },
+   { ["bidi_class"] = "NI" },
+   { ["bidi_class"] = "EN" },
+}
+local test_output = W2(test_input, "L")
+assert(
+   "L" == test_output[1].bidi_class and
+   "NI" == test_output[2].bidi_class and
+   "EN" == test_output[3].bidi_class
+)
+
+-- Test W2: R NI EN → R NI AN
+local test_input = {
+   { ["bidi_class"] = "R" },
+   { ["bidi_class"] = "NI" },
+   { ["bidi_class"] = "EN" },
+}
+local test_output = W2(test_input, "L")
+assert(
+   "R" == test_output[1].bidi_class and
+   "NI" == test_output[2].bidi_class and
+   "EN" == test_output[3].bidi_class
+)
+
 bidi.W3 = function(run)
    -- Change al ALs to R.
    for i = 1, #run do
@@ -244,7 +322,7 @@ end
 
 bidi.resolve_weak_types = function(run, sos)
    run = bidi.W1(run, sos)
-   run = bidi.W2(run, sos)
+   run = W2(run, sos)
    run = bidi.W3(run)
    run = bidi.W4(run)
    run = bidi.W5(run)