OTTL doesn't correctly handle unary signs or certain floating point formats #45222
Description
Component(s)
pkg/ottl
What happened?
Description
I'm trying to write an OTTL plugin for syntax coloring. I needed to write an OTTL grammar, and while doing so I realized there are bugs in OTTL's handling of numeric expressions.
In particular, the OTTL math expression parser did not correctly handle unary signs for plus
and minus. Expressions like "3-5" would not parse correctly. Additionally,
floating point constants that had a decimal point but no fractional digits
(e.g., "3.") were not handled properly and could crash the parser.
Steps to Reproduce
Add this test to Test_lexer in lexer_test.go and run the test. It will fail because "-5" is parsed as a single integer value, but it should not be in this case -- greedy evaluation is generating two ints with no operator.
{"Math Equation nospace", `3-5`, false, []result{
{"Int", "3"},
{typ: "OpAddSub", val: "-"},
{"Int", "5"},
}},A different test is to attempt to parse the value 3. (without trailing digits). It returns an integer 3 and then errors trying to parse the decimal point.
I'm going to submit a PR to fix these issues.
Collector version
v0.142.0
Environment information
Environment
OS: OSX
Compiler(if manually compiled): go 1.25.3
OpenTelemetry Collector configuration
Log output
Additional context
No response
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