[Go] SbeTool generator FormatFlagsConversionMismatchException

[neomantra]

I found a fragility in the SbeTool generator for Golang. I got it to a simple reproducible case.

Process the following schema with java -Dsbe.target.language=Golang -jar sbe-all-1.22.0.jar golang_bug.xml and it will succeed... it will also succeed on all the other generators:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<messageSchema package="gobug" id="1" semanticVersion="1.0" description="Go Bug" byteOrder="littleEndian">
    <types>
        <composite name="Comp1" description="A composite">
            <type name="lmn"  primitiveType="uint16"/>
            <type name="wxyz" primitiveType="uint16"/>
        </composite>
        <composite name="messageHeader" description="Message identifiers and length of message root">z
            <type name="blockLength" primitiveType="uint16"/>
            <type name="templateId"  primitiveType="uint16"/>
            <type name="schemaId"    primitiveType="uint16"/>
            <type name="version"     primitiveType="uint16"/>
            <ref  name="o"           type="Comp1"/>
            <type name="abcd"       primitiveType="uint16"/>
            <ref  name="p"           type="Comp1"/>
        </composite>
    </types>
    <message name="barmsg" id="4">
        <field name="header"   id="1" type="messageHeader"/>
    </message>
</messageSchema>

Change <type name="abcd" to <type name="abcde" and it will fail with this exception:

Exception in thread "main" java.util.FormatFlagsConversionMismatchException: Conversion = s, Flags = 0
        at java.base/java.util.Formatter$FormatSpecifier.failMismatch(Formatter.java:4422)
        at java.base/java.util.Formatter$FormatSpecifier.checkBadFlags(Formatter.java:3151)
        at java.base/java.util.Formatter$FormatSpecifier.checkGeneral(Formatter.java:3109)
        at java.base/java.util.Formatter$FormatSpecifier.<init>(Formatter.java:2870)
        at java.base/java.util.Formatter.parse(Formatter.java:2713)
        at java.base/java.util.Formatter.format(Formatter.java:2655)
        at java.base/java.util.Formatter.format(Formatter.java:2609)
        at java.base/java.lang.String.format(String.java:3292)
        at uk.co.real_logic.sbe.generation.golang.GolangGenerator.generateTypeBodyComposite(GolangGenerator.java:2019)
        at uk.co.real_logic.sbe.generation.golang.GolangGenerator.generateComposite(GolangGenerator.java:1518)
        at uk.co.real_logic.sbe.generation.golang.GolangGenerator.generateTypeBodyComposite(GolangGenerator.java:2040)
        at uk.co.real_logic.sbe.generation.golang.GolangGenerator.generateMessageHeaderStub(GolangGenerator.java:133)
        at uk.co.real_logic.sbe.generation.golang.GolangGenerator.generate(GolangGenerator.java:163)
        at uk.co.real_logic.sbe.SbeTool.generate(SbeTool.java:315)
        at uk.co.real_logic.sbe.SbeTool.main(SbeTool.java:222)

Change <type name="abcd" to <type name="abcdef" and it will succeed!

Or keep <type name="abcd" and change to <type name="wxyz" to <type name="wxy" and it will also fail.

Relevant code link is here:
https://github.com/real-logic/simple-binary-encoding/blob/1.22.0/sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/golang/GolangGenerator.java#L2019

[neomantra]

Added some instrumentation to the generator:

ENCODING  prop: 'BlockLength' longest: 11    fmt: %1s
ENCODING  prop: 'TemplateId' longest: 11    fmt: %2s
ENCODING  prop: 'SchemaId' longest: 11    fmt: %4s
ENCODING  prop: 'Version' longest: 11    fmt: %5s
ENCODING  prop: 'Lmn' longest: 3    fmt: %1s
ENCODING  prop: 'Wxy' longest: 3    fmt: %1s
ENCODING  prop: 'Abcd' longest: 3    fmt: %0s

It's the %0s format string that is causing the problem.

Looks like there's supposed to be an invariant that longest is actually the longest, but that's not happening.

Simply hard-coding the length at line 2019 works with this schema as well as my original schema.

                            .append(String.format("%4s", " "))

[mjpt777]

Was this fixed by the PRs?

[neomantra]

Yes, I will close these issues, thanks!