scip-java: generated Gradle init script is unparseable on Windows — unescaped backslashes in interpolated paths

[carheart]

scip-java: generated Gradle init script is unparseable on Windows — unescaped backslashes in interpolated paths

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 --build-tool gradle entirely on Windows

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Summary

GradleBuildTool.initScript() builds a Groovy init script by string-interpolating absolute
filesystem paths. On Windows those paths contain backslashes, which Groovy parses as escape
sequences inside a double-quoted string. A temp path such as
C:\Users\<name>\AppData\Local\Temp\scip-java-…\gradle-plugin.jar contains \U, which is not a
valid Groovy escape, so the generated script fails to compile and the build never starts.

Unlike the Maven wrapper issue, GradleBuildTool does invoke the correct wrapper on Windows — so
this failure occurs one layer deeper and is reached only after wrapper selection succeeds.

Reproduction

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

The correct command is constructed and launched:

$ C:\…\spring-petclinic\gradlew.bat --no-daemon --init-script C:\Users\…\Temp\scip-java-…\init-script.gradle clean scipPrintDependencies scipCompileAll

then:

init-script.gradle: 3: Unexpected character: '"' @ line 3, column 26.
       classpath(files("C:\Users\carhe\AppData\Local\Temp\scip-java-…\gradle-plugin.jar"))
                       ^

Source

scip-java/src/main/kotlin/org/scip_code/scip_java/buildtools/GradleBuildTool.kt (v0.13.1,
L101-128):

val script =
    """
     initscript {
         dependencies{ 
             classpath(files("${gradlePluginPath}"))
         }
     }

     import org.scip_code.scip_java.gradle.ScipGradlePlugin

     allprojects {
       project.ext["scipTarget"] = "${targetroot()}"
       project.ext["javacPluginJar"] = "$pluginpath"
       project.ext["dependenciesOut"] = "$dependenciesPath"
       project.ext["scipKotlincJar"] = "$scipKotlincPath"
       apply plugin: ScipGradlePlugin
     }
    """
        .trimIndent()

Five interpolated paths are affected, not just the one that reports the error:
gradlePluginPath, targetroot(), pluginpath, dependenciesPath, scipKotlincPath. The parse
fails at the first, so the others are latent — fixing only line 3 would surface the next one.

Whether a given path breaks depends on the character following each backslash: \U (from
\Users) and \A (\AppData) are invalid escapes and hard-error, while e.g. \b/\n/\t would
silently corrupt the path instead. Both outcomes are wrong; only one is loud.

Suggested fix

Groovy accepts forward slashes in paths on Windows, so normalising at interpolation is sufficient
and needs no escaping logic:

fun Path.forGroovy(): String = toString().replace('\\', '/')

then "${gradlePluginPath.forGroovy()}", "${targetroot().forGroovy()}", and the same for the
other three.

Alternative: emit single-quoted Groovy strings (no escape processing), but that only shifts the
problem to any path containing a quote. Forward-slash normalisation is simpler and platform-safe.

Impact

Combined with the Maven wrapper issue, scip-java index has no working code path on Windows in
either 0.12.3 or 0.13.1:

• default / --build-tool maven → CreateProcess error=193 spawning mvnw
• --build-tool gradle → this parse error

No environment workaround exists. In particular, forcing a forward-slash temp directory via
-Djava.io.tmpdir=C:/some/path does not help — the JVM canonicalises java.io.tmpdir back to
backslashes before GradleBuildTool reads it. Verified experimentally.

That both defects survived the full Scala→Kotlin rewrite suggests there is no Windows coverage in
CI. A single smoke test — scip-java index on a wrapper-based fixture on a windows-latest
runner — would catch both.

Environment

• Windows 11 Pro 10.0.26200 (x64), 24 cores
• Eclipse Temurin JDK 17.0.20 and 21.0.12 both present
• Gradle 9.5.1 via gradlew.bat
• scip-java 0.12.3 launched via Coursier (cs launch com.sourcegraph:scip-java_2.13:0.12.3);
  source re-verified against the v0.13.1 tag
• Fixture: spring-petclinic