Update "Command-line flags" page with -Xplugin instructions
#1115
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If run in the old style, it uses javac9, which can't handle the Java 11 class files in the JDK11 bootclasspath. This follows the instructions at https://errorprone.info/docs/installation#maven Note also the need to include -Xep:BetaApi:OFF in the same arg as -Xplugin:ErrorProne: google/error-prone#1136 (comment) google/error-prone#1115 (Also, incidentally update Error Prone itself. I forget whether I had a Java-11-related reason for that, but it seems like a good idea.) RELNOTES=n/a ------------- Created by MOE: https://github.com/google/moe MOE_MIGRATED_REVID=272934125
If run in the old style, it uses javac9, which can't handle the Java 11 class files in the JDK11 bootclasspath. This follows the instructions at https://errorprone.info/docs/installation#maven Note also the need to include -Xep:BetaApi:OFF in the same arg as -Xplugin:ErrorProne: google/error-prone#1136 (comment) google/error-prone#1115 (Also, incidentally update Error Prone itself. I forget whether I had a Java-11-related reason for that, but it seems like a good idea.) RELNOTES=n/a ------------- Created by MOE: https://github.com/google/moe MOE_MIGRATED_REVID=272934125
docs/flags.md
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| </compilerArgs> | ||
| </configuration> | ||
| </build> | ||
| </plugins> | ||
| </plugin> | ||
| </project> | ||
| ``` | ||
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| Be aware that when running on JDK 8 the flags cannot be wrapped across multiple | ||
| lines. JDK 9 and above do allow the flags to be separated by newlines. |
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I'm not sure what this means, was this a JDK change or a maven change? Is it saying that e.g.
<arg>-Xplugin:ErrorProne
-Xep:DeadException:WARN
-Xep:GuardedBy:OFF</arg>
is supported?
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You understood correctly. It's a JDK change, and indeed such formatting is supported on JDK 9 and up. I'll add an example.
(See #1226 for an example where a JDK 8 user hit this issue, and removing the newlines fixed it. With JDK 9+ newlines do work, as shown in e.g. #1136 (comment). Unfortunately I wasn't able to find the OpenJDK commit that fixed this.)
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Tnx for the review @cushon. I rebased and added a commit; PTAL.
docs/flags.md
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| </compilerArgs> | ||
| </configuration> | ||
| </build> | ||
| </plugins> | ||
| </plugin> | ||
| </project> | ||
| ``` | ||
|
|
||
| Be aware that when running on JDK 8 the flags cannot be wrapped across multiple | ||
| lines. JDK 9 and above do allow the flags to be separated by newlines. |
There was a problem hiding this comment.
You understood correctly. It's a JDK change, and indeed such formatting is supported on JDK 9 and up. I'll add an example.
(See #1226 for an example where a JDK 8 user hit this issue, and removing the newlines fixed it. With JDK 9+ newlines do work, as shown in e.g. #1136 (comment). Unfortunately I wasn't able to find the OpenJDK commit that fixed this.)
I migrated a Maven configuration from
javac-with-errorproneto-Xplugin:ErrorProne, as documented in 74726c3. Not being familiar with javac plugins, it took me quite a while before I realized why I was consistently greeted with errors about Error Prone flags not being recognized:It turns out the following doesn't work anymore (like it did with
javac-with-errorprone):Then based on the Ant and command line documentation I tried the following, but this only worked on Java 9+, still failing on Java 8:
The lesson is that for compatibility with Java 8 the flags must either all be on the same line, or in case one wishes to intersperse comments, wrapped like this:
This PR updates the documentation so that others may find a smoother upgrade path :).