sprintf: make negative width left-justify. Fixes #3619

Ary Borenszweig · Ary Borenszweig · commit 49f52ea1e3ab · 2016-12-02T09:25:44.000-03:00
diff --git a/spec/std/string_spec.cr b/spec/std/string_spec.cr
@@ -1395,6 +1395,7 @@ describe "String" do
     ("%20s" % 'a').should eq("                   a")
     ("%-20s" % 'a').should eq("a                   ")
     ("%*s" % [10, 123]).should eq("       123")
+    ("%*s" % [-10, 123]).should eq("123       ")
     ("%.5s" % "foo bar baz").should eq("foo b")
     ("%.*s" % [5, "foo bar baz"]).should eq("foo b")
     ("%*.*s" % [20, 5, "foo bar baz"]).should eq("               foo b")
diff --git a/src/string/formatter.cr b/src/string/formatter.cr
@@ -292,7 +292,7 @@ struct String::Formatter(A)
 
   def pad(consumed, flags)
     padding_char = flags.padding_char
-    (flags.width - consumed).times do
+    (flags.width.abs - consumed).times do
       @io << padding_char
     end
   end
@@ -366,16 +366,12 @@ struct String::Formatter(A)
       @precision_size = 0
     end
 
-    def wants_padding?
-      @width > 0
-    end
-
     def left_padding?
-      wants_padding? && !@minus
+      @minus ? @width < 0 : @width > 0
     end
 
     def right_padding?
-      wants_padding? && @minus
+      @minus ? @width > 0 : @width < 0
     end
 
     def padding_char
