scip-java: `index` fails on Windows — Maven wrapper resolved as `mvnw`, never `mvnw.cmd`

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scip-java: index fails on Windows — Maven wrapper resolved as mvnw, never mvnw.cmd

Repo: scip-code/scip-java
Affected: v0.12.3 (Scala) and v0.13.1 (Kotlin rewrite) — verified in both
Platform: Windows (any); reproduced on Windows 11 Pro 10.0.26200, x64
Severity: blocks scip-java index entirely on Windows for every Maven-wrapper project

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Summary

MavenBuildTool selects the Maven executable by probing for a file literally named mvnw. On
Windows the Maven wrapper is mvnw.cmd; mvnw is a POSIX shell script with no PE header, so
ProcessBuilder.start() fails immediately with CreateProcess error=193.

The fallback branch (else "mvn") is only reached when mvnw is absent — but the file is present
in a standard Maven-wrapper checkout, so on Windows the code takes the broken branch precisely when
a wrapper exists.

Reproduction

git clone https://github.com/spring-projects/spring-petclinic
cd spring-petclinic
scip-java index

On Windows:

java.io.IOException: Cannot run program "c:\…\spring-petclinic\mvnw"
  (in directory "c:\…\spring-petclinic"): CreateProcess error=193,
  %1 is not a valid Win32 application
    at java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java:1170)
    at os.proc.spawn(ProcessOps.scala:129)
    at com.sourcegraph.scip_java.commands.IndexCommand.process(IndexCommand.scala:122)
    at com.sourcegraph.scip_java.buildtools.MavenBuildTool.generateSemanticdb(MavenBuildTool.scala:72)
    at com.sourcegraph.scip_java.buildtools.MavenBuildTool.generateScip(MavenBuildTool.scala:21)
Caused by: java.io.IOException: CreateProcess error=193, %1 is not a valid Win32 application

(mvnw.cmd sits in the same directory, unused.)

Source

scip-java/src/main/kotlin/org/scip_code/scip_java/buildtools/MavenBuildTool.kt (v0.13.1, L22-25):

val mvnw = index.workingDirectory.resolve("mvnw")
val mavenScript =
    if (Files.isRegularFile(mvnw) && Files.isExecutable(mvnw)) mvnw.toString()
    else "mvn"

Identical logic existed in the Scala MavenBuildTool.scala:72 at v0.12.3. Confirmed independently
by extracting strings from the published MavenBuildTool.class in the 0.12.3 release artifact: it
contains exactly mvnw and mvn, with no .cmd variant and no OS branch.

Note Files.isExecutable(mvnw) returns true on Windows for a text file — NTFS has no execute
bit and the JDK reports read access — so the guard does not prevent the bad branch.

Suggested fix

private val isWindows =
    System.getProperty("os.name").orEmpty().startsWith("Windows", ignoreCase = true)

val mavenScript = sequenceOf(
        if (isWindows) index.workingDirectory.resolve("mvnw.cmd") else null,
        index.workingDirectory.resolve("mvnw"),
    )
    .filterNotNull()
    .firstOrNull { Files.isRegularFile(it) }
    ?.toString()
    ?: if (isWindows) "mvn.cmd" else "mvn"

Preferring mvnw.cmd on Windows and keeping mvnw elsewhere is the minimal change. The PATH
fallback likely also wants mvn.cmd on Windows, since a PATH mvn may be a shell script there too.

GradleBuildTool has the same shape at L77 (resolve("gradlew") with no gradlew.bat) and is
worth fixing in the same pass — though in practice Gradle projects fail earlier, for the separate
reason in the companion issue.

Impact

Windows users get a hard failure with a stack trace pointing at ProcessBuilder, which reads as an
environment problem rather than a wrapper-selection bug. There is no flag to work around it:
--build-tool gradle routes to GradleBuildTool, which fails for a different Windows-specific
reason (see companion issue).

Environment

• Windows 11 Pro 10.0.26200 (x64), 24 cores
• Eclipse Temurin JDK 17.0.20 and 21.0.12 both present
• scip-java 0.12.3 launched via Coursier (cs launch com.sourcegraph:scip-java_2.13:0.12.3)
• Fixture: spring-petclinic (ships both mvnw and mvnw.cmd)