Issue2190

>>> unichr (0xD800)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
java.lang.StringIndexOutOfBoundsException: String index out of range: 1
        at java.lang.String.charAt(Unknown Source)
        at org.python.core.PyString.encode_UnicodeEscape(PyString.java:227)
        at org.python.core.PyUnicode.unicode___repr__(PyUnicode.java:245)
        at org.python.core.PyUnicode.__repr__(PyUnicode.java:240)
        at org.python.core.PySystemState.displayhook(PySystemState.java:1518)
        at org.python.core.PySystemStateFunctions.__call__(PySystemState.java:17
12)
        at org.python.core.PyObject.invoke(PyObject.java:3638)
        at org.python.core.Py.printResult(Py.java:1920)
        at org.python.pycode._pyx55.f$0(<stdin>:1)
        at org.python.pycode._pyx55.call_function(<stdin>)
        at org.python.core.PyTableCode.call(PyTableCode.java:165)
        at org.python.core.PyCode.call(PyCode.java:18)
        at org.python.core.Py.runCode(Py.java:1312)
        at org.python.core.Py.exec(Py.java:1356)
        at org.python.util.PythonInterpreter.exec(PythonInterpreter.java:215)
        at org.python.util.InteractiveInterpreter.runcode(InteractiveInterpreter
.java:89)
        at org.python.util.InteractiveInterpreter.runsource(InteractiveInterpret
er.java:70)
        at org.python.util.InteractiveInterpreter.runsource(InteractiveInterpret
er.java:46)
        at org.python.util.InteractiveConsole.push(InteractiveConsole.java:112)
        at org.python.util.InteractiveConsole.interactInteractiveConsole.java:9
3)
        at org.python.util.jython.run(jython.java:396)
        at org.python.util.jython.main(jython.java:145)

java.lang.StringIndexOutOfBoundsException: java.lang.StringIndexOutOfBoundsException: String index out of range: 1

This is a bug in PyString.encode_UnicodeEscape(). When encountering a surrogate character, it doesn't check if there are more characters in the string before attempting to get it with charAt().

We need to throw an appropriate Python error to complete this fix, given that we cannot support such lone surrogates using Jython's underlying UTF-16 representation of Unicode. I suggest ValueError, following this model:

>>> unichr(-1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: unichr() arg not in range(0x110000)

So maybe the text should be somewhat like the following:

ValueError: unichr() arg is a lone surrogate in range (0xD800, 0xDFFF) (Jython UTF-16 encoding)

Target beta 4

I already committed a fix which harmonized the behavior with CPython. But if you say so, then I shall commit a better fix.

Alex, thanks for making this second change. Sorry about the misleading comment indicating support for lone surrogates in the codebase. (Another fix to be made? Not for this bug fix however.)

I left the earlier fix in place as it does no harm. I however replaced the test with something that tests that calling unichr() with a surrogate code results in a ValueError (as Jim suggested) and verified that the test passes.