8341641: Make %APPDATA% and %LOCALAPPDATA% env variables available in *.cfg files

[alexeysemenyukoracle]

jpackage app laucnher will expand environment variables in .cfg files.

Previously jpackage app launcher only replaced $APPDIR, $BINDIR, and $ROOTDIR tokens with the corresponding path values. With this patch, any environment variable can be expanded. The syntax is shell-like $ENV_VAR_NAME or ${ENV_VAR_NAME}. If $ENV_VAR_NAME syntax is used, the variable name stops at the first character outside of [a-zA-Z0-9_] character range. If ${ENV_VAR_NAME} syntax is used, the variable name stops at the first } character after ${ substring. E.g:

String	Variables	Variable Values	Expanded string	Note
Welcome $USER!	USER	USER=John	Welcome John!
Welcome $USER!	USER	not set	Welcome $USER!	Unset variables are not expanded.
Welcome $USER2	USER2	USER2=John	Welcome John!
Welcome ${USER}2	USER	USER=John	Welcome John2!
Welcome $USER-2	USER	USER=John	Welcome John-2!
Welcome ${USER-2}	USER-2	USER-2=John	Welcome John!	USER-2 is likely to be an invalid env variable name, but jpackage launcher is not validating names.

\$ character combination prevents variable expansion:

String	Variables	Variable Values	Expanded string
Hello \$A! Bye $B	B	B=John	Hello $A! Bye John
Hello \${A}! Bye $B	B	B=John	Hello ${A}! Bye John

\\ character combination escapes \:

String	Variables	Variable Values	Expanded string
Hello \\$A! Bye $B	A, B	A=Ana B=John	Hello \Ana! Bye John

If \ character is not followed by another \ character or $ character, it is interpreted as a regular character:

String	Expanded string
a\b\c	a\b\c

Expansion is non-recursive:

String	Variables	Variable Values	Expanded string	Note
Hello $A!	A	A=$B B=John	Hello $B	Variable "B" will not be expanded

Values of APPDIR, BINDIR, and ROOTDIR environment variables are ignored, and these names are substituted by values calculated by jpackage app launcher as previously.

$APPDIR is equivalent to ${APPDIR}.
$BINDIR is equivalent to ${BINDIR}.
$ROOTDIR is equivalent to ${ROOTDIR}.

You will find two entities dealing with token replacement in this patch:

• StringProcessing.cpp/.h - code that performs variable substitution in .cfg files;
• TokenReplace.java - helper class for jpackage tests. It will be later used with other jpackage tests and to implement jdk.jpackage.internal.OverridableResource.substitute() method.

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Progress

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Issue

• JDK-8341641: Make %APPDATA% and %LOCALAPPDATA% env variables available in *.cfg files (Enhancement - P4)

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[bridgekeeper]

👋 Welcome back asemenyuk! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

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[alexeysemenyukoracle]

@sashamatveev PTAL

[mlbridge]

Webrevs

• 02: Full - Incremental (05cbac43)
• 01: Full - Incremental (e5d248a1)
• 00: Full (32f2b529)

[sashamatveev]

If you do echo on macOS in terminal for unset variable it will be expanded to empty string, so for "Unset variables are not expanded." should we have Welcome ! instead of Welcome $USER!?

[sashamatveev]

Looks good overall with minor comment and question.

[sashamatveev]

} else { in one line for consistency.

[openjdk]

⚠️ @alexeysemenyukoracle This pull request contains merges that bring in commits not present in the target repository. Since this is not a "merge style" pull request, these changes will be squashed when this pull request in integrated. If this is your intention, then please ignore this message. If you want to preserve the commit structure, you must change the title of this pull request to Merge <project>:<branch> where <project> is the name of another project in the OpenJDK organization (for example Merge jdk:master).

[alexeysemenyukoracle]

This is true for any shell behavior. It is also true that some shells fail to expand undefined variables if configured accordingly. Bash, for example:

bash -c 'FOO=10; echo FOO=$FOO; unset FOO; set -u; echo FOO=$FOO'

Output:

FOO=10
bash: line 1: FOO: unbound variable

.cfg files are not scripts and jpackage app launcher is not an interpreter. Performed string substitution is less variable expansion and more token replacement; if token value is not available, it is not replaced.
Regardless of handling undefined variables, users have to deal with the consequences. Say they pass --java-options -DmyAppData=$HOME/.myData option to jackage and HOME variable happens undefined on a machine where installed app is launched. How would /.myData be better than $HOME/.myData? At least it is clear something went wrong in the second case.