javaextensiontask.rb - check `javac` path using `JAVA_HOME` #247

MSP-Greg · 2025-04-11T14:50:49Z

JRuby-head is using JDK 21. This is not the default on GHA. setup-ruby added code to change JAVA_HOME, assuming it would trigger the correct JDK being used.

Puma tests against jruby-head, and it was failing when rake compile ran. After reviewing the code, javac is being called without a path.

Added code to check if File.join(ENV["JAVA_HOME"], "bin", "javac") exists. If it does, use the full path, otherwise fallback to current behavior.

I changed the Gemfile in Puma to use the PR branch, and the job correctly compiles.

MSP-Greg · 2025-04-11T16:45:30Z

@headius

Sorry for the ping. You and Pavel have the two most recent commits here. I'm somewhat java challenged. Does this look ok?

JFYI, started with Puma failing on jruby-head...

kou · 2025-04-12T02:48:13Z

lib/rake/javaextensiontask.rb

        EOF
        warn_once(not_jruby_compile_msg) unless defined?(JRUBY_VERSION)

+        javac_path = File.exist?(t = File.join(ENV["JAVA_HOME"], "bin", "javac")) ?


It seems that ENV["JAVA_HOME"] may not exist:

rake-compiler/lib/rake/javaextensiontask.rb

Lines 267 to 268 in 150c8e3

jruby_home = ENV['JRUBY_HOME']

if jruby_home

Can we reuse the checked ENV["JAVA_HOME"] value?

Not sure if ENV["JAVA_HOME"] is used anywhere?

Can we use:

ENV.fetch("JAVA_HOME", "/")

I just pushed a change to using ENV.fetch. Used "/" for the default so it's an absolute path...

Oh, sorry. It's JRUBY_HOME not JAVE_HOME...

kou · 2025-04-12T09:06:05Z

lib/rake/javaextensiontask.rb

+        javac_path = File.exist?(t = File.join(ENV.fetch("JAVA_HOME", "/"), "bin", "javac")) ?
+          t : "javac"


Using / as the default JAVA_HOME will not work when javac exists in both of /usr/bin/javac and /usr/local/bin/javac, and PATH is /usr/local/bin:/usr/bin:/bin.

We may need to check ENV["JAVA_HOME"] explicitly:

Suggested change

javac_path = File.exist?(t = File.join(ENV.fetch("JAVA_HOME", "/"), "bin", "javac")) ?

t : "javac"

java_home = ENV["JAVA_HOME"]

if java_home

javac_path = File.join(java_home, "bin", "javac")

javac_path = nil unless File.exist?(javac_path)

end

javac_path ||= "javac"

@kou

Thanks for the review. I'm not sure about your example, it seems a rather extreme and odd edge case. Also, I'm not familiar with all of the *nix distributions.

"/" was a bad choice for default, as File.join('/', 'bin', 'javac')" and File.join('', 'bin', 'javac') both equal "/bin/javac".

The previous code worked correctly when used with GHA. But your changes also work.

Updated with your suggested code.

Oh, sorry. I considered the following case:

ENV["PATH"] is "/usr/local/bin:/usr/bin

ENV["JAVA_HOME"] isn't set

/usr/local/bin/javac exists

/usr/bin/javac exists

In the case, javac uses /usr/local/bin/javac but File.join(ENV.fetch("JAVA_HOME", "/"), "bin", "javac") uses /usr/bin/javac not /usr/local/bin/javac.

Sorry, I need to try this.

If ENV["JAVA_HOME"] isn't set, then ENV.fetch("JAVA_HOME", "/"), "bin", "javac") yields /bin/javac, I thought File.exist?("/bin/javac") would be false, and then javac would be used, and the file would be resolved by PATH?

Again, I need to try it.

Regardless, thanks for your help and the new release.

MSP-Greg · 2025-04-12T14:24:01Z

Some background on this issue.

At present, GitHub Actions (GHA) runners provide at least three Java versions (11, 17, 21). Some provide version 8. Version 17 is the default. ENV variables exist for determining the location of each version.

JRuby 10/head requires version 21. setup-ruby made changes for this by changing the value of ENV['JAVA_HOME'].

This PR finishes the work by using ENV['JAVA_HOME'] to determine the path for the correct version of javac to run for the compile process.

kou · 2025-04-13T00:11:05Z

@headius I'll merge this and release a new version.

If you have any problem with this, please share it.

eregon · 2025-12-13T17:05:14Z

Thanks for this PR.

It works fine on UNIX but not Windows:
https://github.com/eregon/actions-shell/actions/runs/20195116809/job/57977991482#step:4:369

ENV["JAVA_HOME"]
"C:\\hostedtoolcache\\windows\\Java_Temurin-Hotspot_jdk\\21.0.9-10.0\\x64"

File.join(ENV["JAVA_HOME"], "bin", "javac")
"C:\\hostedtoolcache\\windows\\Java_Temurin-Hotspot_jdk\\21.0.9-10.0\\x64/bin/javac"

File.exist?(File.join(ENV["JAVA_HOME"], "bin", "javac"))
false

I'm unsure if it's a bug of File.join on JRuby on Windows (the code does File.join(java_home, "bin", "javac") which intuitively should work, either use only \ or convert everything to / but a mix seems quite broken).
cc @headius

eregon · 2025-12-13T17:12:44Z

It seems File.join does have those "broken" semantics even on CRuby :/
https://github.com/eregon/actions-shell/actions/runs/20195181454/job/57978154719#step:4:798

JAVA_HOME = "C:\\hostedtoolcache\\windows\\Java_Temurin-Hotspot_jdk\\21.0.9-10.0\\x64"
File.join(JAVA_HOME, "bin", "javac")
"C:\\hostedtoolcache\\windows\\Java_Temurin-Hotspot_jdk\\21.0.9-10.0\\x64/bin/javac"

So I guess we should just hack it with

File.join(java_home.tr('\\', '/'), "bin", "javac")

then, or seeing that File.join is beyond useless here, just:

"#{java_home.tr('\\', '/')}/bin/javac"

eregon · 2025-12-13T17:27:13Z

Oof even that doesn't work, Windows is truly cursed IMO:
https://github.com/eregon/actions-shell/actions/runs/20195353255/job/57978552583#step:4:377

"#{JAVA_HOME.tr('\\', '/')}/bin/javac"
"C:/hostedtoolcache/windows/Java_Temurin-Hotspot_jdk/21.0.9-10.0/x64/bin/javac"

File.exist?("#{JAVA_HOME.tr('\\', '/')}/bin/javac")
false

At this point I'll let others investigate/fix it.

eregon · 2025-12-13T18:36:08Z

Ah, it's my mistake on Windows there is no bin/javac, it's bin/javac.exe.
Then all of them work:

 File.join(JAVA_HOME, "bin", "javac.exe")
"C:\\hostedtoolcache\\windows\\Java_Temurin-Hotspot_jdk\\21.0.9-10.0\\x64/bin/javac.exe"

File.exist?(File.join(JAVA_HOME, "bin", "javac.exe"))
true

"#{JAVA_HOME.tr('\\', '/')}/bin/javac.exe"
"C:/hostedtoolcache/windows/Java_Temurin-Hotspot_jdk/21.0.9-10.0/x64/bin/javac.exe"

File.exist?("#{JAVA_HOME.tr('\\', '/')}/bin/javac.exe")
true

"#{JAVA_HOME}\\bin\\javac.exe"
"C:\\hostedtoolcache\\windows\\Java_Temurin-Hotspot_jdk\\21.0.9-10.0\\x64\\bin\\javac.exe"

File.exist?("#{JAVA_HOME}\\bin\\javac.exe")
true

Sanity has returned.

eregon · 2025-12-13T18:41:36Z

@kou so there is db38e70 but https://rubygems.org/gems/rake-compiler only has 1.3.0 not 1.3.1, so it seems you forgot to push the gem or it didn't work?
Could you push 1.3.1 (or 1.3.2 if 1.3.1 is not possible?)

That would also explain why CI failed on ruby/strscan#155

And now I found the discussion I recalled: ruby/strscan#151
I had hope @headius would look into this before we run into this again.

eregon · 2025-12-13T19:52:27Z

@headius IMO this is messy enough that I think it would be better to add JAVA_HOME/bin to PATH in setup-ruby.
I don't see a disadvantage to do so, setup-java would do the same thing and it's likely to work poorly to have java in PATH different than JAVA_HOME/bin/java (e.g. javac uses PATH, Maven uses JAVA_HOME, a wild mix).

* See discussion in rake-compiler/rake-compiler#247 it is messy if that's not the case and also creates inconsistencies based on which Java tool/executable is used.

eregon · 2025-12-13T20:00:34Z

I went ahead and did a PR to do that so we can't run into such issues again: ruby/setup-ruby#836

* See discussion in rake-compiler/rake-compiler#247 it is messy if that's not the case and also creates inconsistencies based on which Java tool/executable is used.

kou · 2025-12-14T01:39:13Z

Oh, sorry. I didn't notice it.

I've published 1.3.1.

MSP-Greg mentioned this pull request Apr 11, 2025

[ci] use java 21 on jruby 10 puma/puma#3647

Closed

7 tasks

MSP-Greg force-pushed the 00-java-home branch 2 times, most recently from 7ba0151 to da7dea5 Compare April 12, 2025 01:21

kou reviewed Apr 12, 2025

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MSP-Greg force-pushed the 00-java-home branch from da7dea5 to 6f51483 Compare April 12, 2025 03:56

kou reviewed Apr 12, 2025

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javaextensiontask.rb - check javac path using JAVA_HOME

98ada08

MSP-Greg force-pushed the 00-java-home branch from 6f51483 to 98ada08 Compare April 12, 2025 13:19

kou merged commit c413d3b into rake-compiler:master Apr 13, 2025
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MSP-Greg deleted the 00-java-home branch April 13, 2025 03:22

eregon mentioned this pull request Dec 13, 2025

Replace C extension ToRuby#init_data with Data#initialize bind_call ruby/psych#765

Open

eregon mentioned this pull request Dec 13, 2025

Remove unnecessary actions/setup-java ruby/strscan#155

Merged

eregon mentioned this pull request Dec 13, 2025

When setting $JAVA_HOME also add $JAVA_HOME/bin to PATH ruby/setup-ruby#836

Merged

		javac_path = File.exist?(t = File.join(ENV.fetch("JAVA_HOME", "/"), "bin", "javac")) ?
		t : "javac"

-        javac_path = File.exist?(t = File.join(ENV.fetch("JAVA_HOME", "/"), "bin", "javac")) ?
-          t : "javac"
+        java_home = ENV["JAVA_HOME"]
+        if java_home
+          javac_path = File.join(java_home, "bin", "javac")
+          javac_path = nil unless File.exist?(javac_path)
+       end
+       javac_path ||= "javac"

javaextensiontask.rb - check javac path using JAVA_HOME #247

javaextensiontask.rb - check javac path using JAVA_HOME #247

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javaextensiontask.rb - check `javac` path using `JAVA_HOME` #247

javaextensiontask.rb - check `javac` path using `JAVA_HOME` #247

MSP-Greg commented Apr 11, 2025 •

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eregon commented Dec 13, 2025 •

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