Fixes #6825

Summary

sbt -mem 10000 -client fails because launcher-only flags leak through to the native thin client (sbtn), which doesn't understand them.

Problem

runNativeClient() in the bash launcher only strips --client and forwards everything else to sbtn. So sbtn receives -mem 10000, and NetworkClient.parseArgs() misclassifies them: -mem goes to sbtArguments, 10000 goes to commandArgs. The server start command becomes sbt -mem --detach-stdio --server, which fails because -mem has no value.

$ sbt -mem 10000 -client
[info] entering *experimental* thin client - BEEP WHIRR
[info] server was not detected. starting an instance
[error] failed to connect to server

Solution

1. Bash launcher (sbt): allowlist-based arg forwarding

Replace the naive --client stripping in runNativeClient() with an allowlist loop. Only -D* properties, -bsp, --sbt-launch-jar, and non-flag command args are forwarded to sbtn. All launcher-specific flags are categorized and skipped:

• Value-taking flags (-mem, -jvm-debug, -java-home, etc.): skip flag + next arg
• No-value flags (--client, -batch, -debug, etc.): skip flag
• Eq-syntax flags (--supershell=false, --color=never): skip
• -J* JVM flags: skip

2. Defense-in-depth in NetworkClient.parseArgs()

Added matching launcher flag sets and corresponding match cases so that even if launcher flags somehow reach sbtn, they are silently dropped instead of being misclassified as sbt arguments or commands.

3. Unit tests for NetworkClient.parseArgs()

18 test cases covering:

• Value-taking flags (-mem 10000, -jvm-debug 5005, -java-home /path)
• No-value flags (--client, -debug, -batch, -allow-empty)
• Eq-syntax flags (--supershell=false, --color=never)
• -J* JVM flags
• Preserved flags (-Dfoo=bar, -bsp, --sbt-launch-jar, --sbt-script)
• Combined/integration scenarios

Test results

sbt commandProj/test — 38/38 pass:

[info] sbt.internal.client.NetworkClientParseArgsTest
[info] - -mem 10000 compile drops -mem and its value
[info] - --mem 10000 compile drops --mem and its value
[info] - -jvm-debug 5005 compile drops both flag and port
[info] - -java-home /path/to/jdk compile drops both
[info] - -mem at end of args with no value does not crash
[info] - --client compile drops --client
[info] - -client compile drops -client
[info] - -debug is dropped
[info] - -batch is dropped
[info] - -allow-empty is dropped
[info] - --supershell=false is dropped
[info] - --color=never is dropped
[info] - -J-Xss4m is dropped
[info] - -Dfoo=bar compile forwards -D property to sbtArguments
[info] - -bsp is still recognized
[info] - --sbt-launch-jar is preserved
[info] - --sbt-script is preserved
[info] - combined: -mem 10000 -Dfoo=bar compile test
[info] - combined: --client -batch -java-home /jdk --color=never -Dfoo=bar compile
[info] Passed: Total 38, Failed 0, Errors 0, Passed 38

Verification

• sbt commandProj/compile passes
• sbt commandProj/test — 38/38 pass
• sbt scalafmtCheckAll passes
• sbt scalafmtSbtCheck passes

Generated-by: Claude Code (claude.ai/code)