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https://issues.apache.org/jira/browse/MCOMPILER-572?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17811131#comment-17811131
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Mikkel Kjeldsen commented on MCOMPILER-572:
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bq. The value you have provided deliberately contains a space?
It deliberately contains an escaped line break, which {{javac}} will reliably
interpret as a single argument, because that's how the {{-Xplugin}} option must
be used. In other words, a hypothetical
{code:xml}
<arg>-Xplugin:ErrorProne</arg>
<arg>-Xep:DeadException:WARN</arg>
{code}
is an incorrect invocation of {{javac}}.
bq. If so, why are you try to add a line separator to it?
Because, not obvious from the reproduction sample I supplied, the Error Prone
plugin accepts _a lot_ of arguments and these are much, much easier to organize
across multiple lines. One example of that I have handy is
{{jackson-databind}}, which stretches its configuration over 70 lines, at
https://github.com/FasterXML/jackson-databind/blob/2.17/pom.xml#L468-L541;
although {{jackson-databind}} uses the in-process compiler which doesn't
require escaping line breaks.
bq. There is no code in this plugin to manage that.
I am aware of this. All that code is in {{plexus-compiler}} (specifically its
{{JavacCompiler}}), as I have stated. However, I am a consumer of
{{maven-compiler-plugin}} wherein the error manifests, not of
{{plexus-compiler}} wherein the error originates, so only filing a ticket with
{{plexus-compiler}} is insufficient.
> Multi-line <arg> does not work on Windows when forked
> -----------------------------------------------------
>
> Key: MCOMPILER-572
> URL: https://issues.apache.org/jira/browse/MCOMPILER-572
> Project: Maven Compiler Plugin
> Issue Type: Bug
> Affects Versions: 3.12.1
> Reporter: Mikkel Kjeldsen
> Priority: Major
> Fix For: waiting-for-feedback
>
>
> Versions of {{maven-compiler-plugin}} that rely on
> {{plexus-compiler-2.14.2}}, hereunder {{maven-compiler-plugin-3.12.1}},
> cannot pass multi-line compiler arguments to a forked {{javac}} on Windows in
> any way. Further, attempting to do so produces a non-obvious and difficult to
> troubleshoot error. This error does not manifest outside of Windows, nor does
> it manifest on Windows if the compiler is not forked.
> This bug is a downstream version of
> https://github.com/codehaus-plexus/plexus-compiler/issues/351, filed in
> response to https://github.com/google/error-prone/issues/4256.
> The sample POM
> {code:xml}
> <?xml version="1.0" encoding="UTF-8"?>
> <project xmlns="http://maven.apache.org/POM/4.0.0";
> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
> xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
> http://maven.apache.org/xsd/maven-4.0.0.xsd";>
> <modelVersion>4.0.0</modelVersion>
> <groupId>example.multi-line-fork-crash</groupId>
> <artifactId>minimally-reproducible</artifactId>
> <version>1.0-SNAPSHOT</version>
> <properties>
> <maven.compiler.release>21</maven.compiler.release>
> <maven-compiler-plugin.version>3.12.1</maven-compiler-plugin.version>
> </properties>
> <build>
> <plugins>
> <plugin>
> <groupId>org.apache.maven.plugins</groupId>
> <artifactId>maven-compiler-plugin</artifactId>
> <version>${maven-compiler-plugin.version}</version>
> <configuration>
> <fork>true</fork>
> <compilerArgs>
> <arg>
> -Xplugin:ErrorProne \
> -Xep:DeadException:WARN</arg>
> </compilerArgs>
> </configuration>
> </plugin>
> </plugins>
> </build>
> </project>
> {code}
> _should_ fail to compile with the error
> {noformat}
> plug-in not found: ErrorProne
> {noformat}
> but instead fails with the error
> {noformat}
> error: invalid flag: -Xep:DeadException
> {noformat}
> because {{plexus-compiler}} indiscriminately translates the \ to / and breaks
> {{javac}} 's multi-line argument support.
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