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…t timezone Grant Klopper first made this change to the Frontend codebase in June 2014 with #4713 - he explained: > "dev machines will now run in a far away timezone so it is more obvious when you get a timezone wrong" With the wonderful work to drop the custom `sbt` script in #28599 in January 2026, we weren't sure (#28599 (comment)) if we could keep the helpful comment explaining why the timezone was used - can the `.jvmopts` file, where the setting now lives, accept comments!? It turns out `sbt` takes the input from `.jvmopts` here, calling `$(loadConfigFile .jvmopts)`: https://github.com/sbt/sbt/blob/v1.12.2/sbt#L869 The `loadConfigFile()` function reads in each line of the file, and crucially calls `eval` on it: ``` eval echo $line ``` https://github.com/sbt/sbt/blob/v1.12.2/sbt#L771 The definition of `eval` is: > "The eval utility shall construct a command by concatenating arguments together, separating each with a <space>. The constructed command shall be read and executed by the shell." The upshot is that this line of input: ``` -Duser.timezone=Australia/Sydney # because it is too easy for devs ``` ...becomes the shell evaluation of: ``` echo -Duser.timezone=Australia/Sydney # because it is too easy for devs ``` ...which as far as the shell is concerned, is just: ``` echo -Duser.timezone=Australia/Sydney ``` ...so we _are_ allowed comments! This behaviour was added to the sbt launcher script with this commit in June 2013, as part of sbt/sbt#6458: sbt/sbt@1835225 We can double-check it works by running `sbt -v` to see the arguments the launcher script passed to Java: ``` % sbt -v [sbt_options] declare -a sbt_options='()' [process_args] java_version = '11' [copyRt] java9_rt = '/Users/roberto_tyley/.sbt/1.0/java9-rt-ext-amazon_com_inc__11_0_22/rt.jar' # Executing command line: java -Xmx8G -XX:ReservedCodeCacheSize=128m -XX:NewRatio=4 -Duser.timezone=Australia/Sydney -DSTAGE=DEV -DAPP_SECRET=this_is_not_a_real_secret_just_for_tests -Dsbt.script=/opt/homebrew/Cellar/sbt/1.12.0/libexec/bin/sbt -Dscala.ext.dirs=/Users/roberto_tyley/.sbt/1.0/java9-rt-ext-amazon_com_inc__11_0_22 -jar /opt/homebrew/Cellar/sbt/1.12.0/libexec/bin/sbt-launch.jar [info] welcome to sbt 1.12.2 (Amazon.com Inc. Java 11.0.22) ```
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Seen on FRONTS-PROD, ADMIN-PROD (merged by @rtyley 14 minutes and 32 seconds ago)
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Ha amazing, thanks @rtyley 👏 |
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Grant Klopper first made this change to the Frontend codebase in June 2014 with #4713 - he explained:
With the wonderful work to drop the custom
sbtscript in #28599 in January 2026, we weren't sure (#28599 (comment)) if we could keep the helpful comment explaining why the timezone was used - can the.jvmoptsfile, where the setting now lives, accept comments!?How does
sbtparse.jvmopts?It turns out
sbttakes the input from.jvmoptshere, calling$(loadConfigFile .jvmopts)- theloadConfigFile()function reads in each line of the file, and crucially callsevalon it:evalis a built-in Linux command:The upshot is that this line of input:
...becomes the shell evaluation of:
...which as far as the shell is concerned, is just:
...so we are allowed comments!
This behaviour was added to the sbt launcher script with this commit in June 2013, as part of sbt/sbt#6458.
We can double-check it works by running
sbt -vto see the arguments the launcher script passed to Java: