Ruiqi Dong created MATH-1681:
--------------------------------
Summary: ComplexFormat.parse(String) returns null instead of
throwing MathParseException for invalid complex number strings
Key: MATH-1681
URL: https://issues.apache.org/jira/browse/MATH-1681
Project: Commons Math
Issue Type: Bug
Components: legacy
Affects Versions: 4.0-beta1
Reporter: Ruiqi Dong
The {{ComplexFormat.parse(String source)}} method violates its documented
contract by returning {{null}} instead of throwing {{MathParseException}} for
certain malformed complex number strings. According to the JavaDoc, the method
should "throw MathParseException if the beginning of the specified string
cannot be parsed," but it fails to do so in several cases.
*Test Case to Demonstrate the Bug:*
{code:java}
@Test
public void
testParseShouldThrowExceptionForInvalidComplexMissingImaginaryCharacter() {
ComplexFormat format = new ComplexFormat();
String invalidComplex = "3 + 5";
assertThrows(MathParseException.class, () -> {
format.parse(invalidComplex);
}, "Parsing '3 + 5' should throw MathParseException due to missing
imaginary character 'i'");
} {code}
{*}Test Result:{*}{*}{*}
{code:java}
{code}
*org.opentest4j.AssertionFailedError: Expected
org.apache.commons.math4.legacy.exception.MathParseException to be thrown, but
nothing was thrown.*
*Root Cause Analysis:*
The bug occurs due to incomplete error handling in the interaction between
{{parse(String)}} and {{parse(String, ParsePosition)}} methods.
When parsing "3 + 5":
# The parser successfully reads "3" (real part), advancing the index from 0 to
1
# It reads "+" (operator), advancing the index further
# It reads "5" (imaginary coefficient), advancing the index to 5
# It fails to find the imaginary character 'i'
# At this point, {{parse(String, ParsePosition)}} returns {{null}} BUT does
not reset the position index
{code:java}
// In parse(String source, ParsePosition pos)
// parse imaginary character
if (!CompositeFormat.parseFixedstring(source, getImaginaryCharacter(), pos)) {
return null; // Bug: position index is not reset to initialIndex
}{code}
# Back in {{{}parse(String){}}}, the check {{if (parsePosition.getIndex() ==
0)}} evaluates to false (index is 5)
# The method returns {{null}} without throwing an exception
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
