handle nil values sent to printerr

ci/test.lua

@@ -270,6 +270,7 @@ local function detect_printerr(func)
     local saved_printerr = dfhack.printerr
     local printerr_called = false
     dfhack.printerr = function(msg)
+            if msg == nil then return end
             saved_printerr(msg)
             printerr_called = true
         end

library/lua/test_util/expect.lua

@@ -164,7 +164,7 @@ function expect.printerr_match(matcher, func, comment)
         function() dfhack.printerr = saved_printerr end,
         func)
     if type(matcher) ~= 'table' then matcher = {matcher} end
-    while messages[1] do
+    while #messages > 0 do
         local msg = messages[1]
         if matches(msg, matcher[1]) then
             table.remove(matcher, 1)

test/library/test_util/expect_unit.lua

@@ -59,20 +59,6 @@ function test.printerr_match()
     local oneprint = function()
         dfhack.printerr('a')
     end
-    local twoprint = function()
-        dfhack.printerr('a')
-        dfhack.printerr('b')
-    end
-    local threeprint = function()
-        dfhack.printerr('a')
-        dfhack.printerr('b')
-        dfhack.printerr('c')
-    end
-    local multiprint = function()
-        dfhack.printerr('a')
-        dfhack.printerr('b')
-        dfhack.printerr('a')
-    end
 
     expect.true_(expect_raw.printerr_match(nil, noprint))
     expect.true_(expect_raw.printerr_match({}, noprint))
@@ -90,6 +76,10 @@ function test.printerr_match()
     expect.false_(expect_raw.printerr_match({b=1}, oneprint))
     expect.false_(expect_raw.printerr_match({a=1,b=1}, oneprint))
 
+    local twoprint = function()
+        dfhack.printerr('a')
+        dfhack.printerr('b')
+    end
     expect.true_(expect_raw.printerr_match({'a','b'}, twoprint))
     expect.true_(expect_raw.printerr_match({a=1,b=1}, twoprint))
     expect.false_(expect_raw.printerr_match({'b','a'}, twoprint))
@@ -98,8 +88,29 @@ function test.printerr_match()
     expect.false_(expect_raw.printerr_match({a=1,b=2}, twoprint))
     expect.false_(expect_raw.printerr_match({a=1,b=1,c=1}, twoprint))
 
+    local threeprint = function()
+        dfhack.printerr('a')
+        dfhack.printerr('b')
+        dfhack.printerr('c')
+    end
     expect.true_(expect_raw.printerr_match({a=1,b=1,c=1}, threeprint))
 
+    local multiprint = function()
+        dfhack.printerr('a')
+        dfhack.printerr('b')
+        dfhack.printerr('a')
+    end
     expect.true_(expect_raw.printerr_match({a=2,b=1}, multiprint))
     expect.false_(expect_raw.printerr_match({a=1,b=1}, multiprint))
+
+    local nilprint = function()
+        dfhack.printerr()
+    end
+    expect.true_(expect_raw.printerr_match({}, nilprint))
+
+    local nilaprint = function()
+        dfhack.printerr()
+        dfhack.printerr('a')
+    end
+    expect.true_(expect_raw.printerr_match({'a'}, nilaprint))
 end