add safe_pairs, update unit tests

library/lua/dfhack.lua

@@ -162,11 +162,33 @@ NEWLINE = "\n"
 COMMA = ","
 PERIOD = "."
 
+local function _wrap_iterator(next_fn, ...)
+    local wrapped_iter = function(...)
+        local ret = {pcall(next_fn, ...)}
+        local ok = table.remove(ret, 1)
+        if ok then
+            return table.unpack(ret)
+        end
+    end
+    return wrapped_iter, ...
+end
+
+function safe_pairs(t, iterator_fn)
+    iterator_fn = iterator_fn or pairs
+    if (pcall(pairs, t)) then
+        return _wrap_iterator(iterator_fn(t))
+    else
+        return function() end
+    end
+end
+
 -- calls elem_cb(k, v) for each element of the table
 -- returns true if we iterated successfully, false if not
-local function safe_iterate(table, iterate_fn, elem_cb)
+-- this differs from safe_pairs() above in that it only calls pcall() once per
+-- full iteration and it returns whether iteration succeeded or failed.
+local function safe_iterate(table, iterator_fn, elem_cb)
     local function iterate()
-        for k,v in iterate_fn(table) do elem_cb(k, v) end
+        for k,v in iterator_fn(table) do elem_cb(k, v) end
     end
     return pcall(iterate)
 end

test/library/misc.lua

@@ -0,0 +1,21 @@
+-- tests misc functions added by dfhack.lua
+
+function test.safe_pairs()
+    for k,v in safe_pairs(nil) do
+        expect.fail('nil should not be iterable')
+    end
+    for k,v in safe_pairs('a') do
+        expect.fail('a string should not be iterable')
+    end
+    for k,v in safe_pairs({}) do
+        expect.fail('an empty table should not be iterable')
+    end
+
+    local iterated = 0
+    local t = {a='hello', b='world', [1]='extra'}
+    for k,v in safe_pairs(t) do
+        expect.eq(t[k], v)
+        iterated = iterated + 1
+    end
+    expect.eq(3, iterated)
+end

test/library/print.lua

@@ -19,32 +19,27 @@ end
 
 function test.printall_string()
     printall('a')
-    expect.eq(1, mock_print.call_count)
+    expect.eq(0, mock_print.call_count)
-    expect.eq('a', mock_print.call_args[1][1])
 end
 
 function test.printall_number()
     printall(10)
-    expect.eq(1, mock_print.call_count)
+    expect.eq(0, mock_print.call_count)
-    expect.eq('10', mock_print.call_args[1][1])
 end
 
 function test.printall_nil()
     printall(nil)
-    expect.eq(1, mock_print.call_count)
+    expect.eq(0, mock_print.call_count)
-    expect.eq('nil', mock_print.call_args[1][1])
 end
 
 function test.printall_boolean()
     printall(false)
-    expect.eq(1, mock_print.call_count)
+    expect.eq(0, mock_print.call_count)
-    expect.eq('false', mock_print.call_args[1][1])
 end
 
 function test.printall_function()
     printall(function() end)
-    expect.eq(1, mock_print.call_count)
+    expect.eq(0, mock_print.call_count)
-    expect.true_(mock_print.call_args[1][1]:find('^function: 0x'))
 end
 
 function test.printall_userdata()
@@ -60,32 +55,27 @@ end
 
 function test.printall_ipairs_string()
     printall_ipairs('a')
-    expect.eq(1, mock_print.call_count)
+    expect.eq(0, mock_print.call_count)
-    expect.eq('a', mock_print.call_args[1][1])
 end
 
 function test.printall_ipairs_number()
     printall_ipairs(10)
-    expect.eq(1, mock_print.call_count)
+    expect.eq(0, mock_print.call_count)
-    expect.eq('10', mock_print.call_args[1][1])
 end
 
 function test.printall_ipairs_nil()
     printall_ipairs(nil)
-    expect.eq(1, mock_print.call_count)
+    expect.eq(0, mock_print.call_count)
-    expect.eq('nil', mock_print.call_args[1][1])
 end
 
 function test.printall_ipairs_boolean()
     printall_ipairs(false)
-    expect.eq(1, mock_print.call_count)
+    expect.eq(0, mock_print.call_count)
-    expect.eq('false', mock_print.call_args[1][1])
 end
 
 function test.printall_ipairs_function()
     printall_ipairs(function() end)
-    expect.eq(1, mock_print.call_count)
+    expect.eq(0, mock_print.call_count)
-    expect.true_(mock_print.call_args[1][1]:find('^function: 0x'))
 end
 
 function test.printall_ipairs_userdata()