Fix StringIO#{gets, readline} when it is called with both separator and limit to truncate the separator if the limit is exceeded

Author: andrykonchin

CHANGELOG.md

@@ -23,6 +23,7 @@ Compatibility:
 * Fix `Kernel#raise` and don't override `cause` at exception re-raising (#3831, @andrykonchin).
 * Return a pointer with `#type_size` of 1 for `Pointer#read_pointer` (@eregon).
 * Fix `rb_str_locktmp()` and `rb_str_unlocktmp()` to raise `FrozenError` when string argument is frozen (#3752, @andrykonchin).
+* Fix `StringIO#{gets,readline}` when it is called with both separator and limit to truncate the separator if the limit is exceeded (#3856, @andrykonchin).
 
 Performance:
 

lib/truffle/stringio.rb

@@ -779,7 +779,7 @@ def yaml_initialize(type, val)
         end
       else
         if stop = Primitive.find_string(string, sep, pos)
-          if limit && stop - pos >= limit
+          if limit && stop - pos + sep.bytesize >= limit
             stop = pos + limit
           else
             stop += sep.bytesize

spec/ruby/library/stringio/gets_spec.rb

@@ -190,6 +190,10 @@
     @io.gets('>', 5).should == "examp"
   end
 
+  it "truncates the multi-character separator at the end to meet the limit" do
+    @io.gets("is>an", 7).should == "this>is"
+  end
+
   it "sets $_ to the read content" do
     @io.gets('>', 8)
     $_.should == "this>"

spec/ruby/library/stringio/readline_spec.rb

@@ -148,3 +148,61 @@
     @io.readline(-4).should == "this>is>an>example"
   end
 end
+
+describe "StringIO#readline when passed [separator] and [limit]" do
+  before :each do
+    @io = StringIO.new("this>is>an>example")
+  end
+
+  it "returns the data read until the limit is consumed or the separator is met" do
+    @io.readline('>', 8).should == "this>"
+    @io.readline('>', 2).should == "is"
+    @io.readline('>', 10).should == ">"
+    @io.readline('>', 6).should == "an>"
+    @io.readline('>', 5).should == "examp"
+  end
+
+  it "truncates the multi-character separator at the end to meet the limit" do
+    @io.readline("is>an", 7).should == "this>is"
+  end
+
+  it "sets $_ to the read content" do
+    @io.readline('>', 8)
+    $_.should == "this>"
+    @io.readline('>', 2)
+    $_.should == "is"
+    @io.readline('>', 10)
+    $_.should == ">"
+    @io.readline('>', 6)
+    $_.should == "an>"
+    @io.readline('>', 5)
+    $_.should == "examp"
+  end
+
+  it "updates self's lineno by one" do
+    @io.readline('>', 3)
+    @io.lineno.should eql(1)
+
+    @io.readline('>', 3)
+    @io.lineno.should eql(2)
+
+    @io.readline('>', 3)
+    @io.lineno.should eql(3)
+  end
+
+  it "tries to convert the passed separator to a String using #to_str" do
+    obj = mock('to_str')
+    obj.should_receive(:to_str).and_return('>')
+    @io.readline(obj, 5).should == "this>"
+  end
+
+  it "does not raise TypeError if passed separator is nil" do
+    @io.readline(nil, 5).should == "this>"
+  end
+
+  it "tries to convert the passed limit to an Integer using #to_int" do
+    obj = mock('to_int')
+    obj.should_receive(:to_int).and_return(5)
+    @io.readline('>', obj).should == "this>"
+  end
+end