On Thu, 6 Mar 2025 15:25:13 GMT, Alexey Semenyuk <asemen...@openjdk.org> wrote:
>> 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 |
>> | -------- | ------- |------- |------- |------- |
>> | <pre>Welcome $USER!</pre> | <pre>USER</pre> | <pre>USER=John</pre> |
>> <pre>Welcome John!</pre> ||
>> | <pre>Welcome $USER!</pre> | <pre>USER</pre> | <pre>not set</pre> |
>> <pre>Welcome $USER!</pre> | Unset variables are not expanded. |
>> | <pre>Welcome $USER2</pre> | <pre>USER2</pre> | <pre>USER2=John</pre> |
>> <pre>Welcome John!</pre> ||
>> | <pre>Welcome ${USER}2</pre> | <pre>USER</pre> | <pre>USER=John</pre> |
>> <pre>Welcome John2!</pre> ||
>> | <pre>Welcome $USER-2</pre> | <pre>USER</pre> | <pre>USER=John</pre> |
>> <pre>Welcome John-2!</pre> ||
>> | <pre>Welcome ${USER-2}</pre> | <pre>USER-2</pre> |
>> <pre>USER-2=John</pre> | <pre>Welcome John!</pre> | `USER-2` is likely to be
>> an invalid env variable name, but jpackage launcher is not validating names.
>> |
>>
>> `$` character combination prevents variable expansion:
>> | String | Variables | Variable Values | Expanded string |
>> | -------- | ------- |------- |------- |
>> | <pre>Hello \$A! Bye $B</pre> | B | <pre>B=John</pre> | <pre>Hello $A! Bye
>> John</pre> |
>> | <pre>Hello \${A}! Bye $B</pre> | B | <pre>B=John</pre> | <pre>Hello ${A}!
>> Bye John</pre> |
>>
>> `\` character combination escapes ``:
>> | String | Variables | Variable Values | Expanded string |
>> | -------- | ------- |------- |------- |
>> | <pre>Hello \\\$A! Bye $B</pre> | A, B | <pre>A=Ana</pre><pre>B=John</pre>
>> | <pre>Hello \\Ana! Bye John</pre> |
>>
>> If `` character is not followed by another `` character or `$` character, it
>> is interpreted as a regular character:
>> | String | Expanded string |
>> | -------- | ------- |
>> |<pre>a\\b\\c</pre>|<pre>a\\b\\c</pre>|
>>
>>
>> Expansion is non-recursive:
>> | String | Variables | Variable Values | Expanded string | Note |
>> | -------- | ------- |------- |------- |------- |
>> | <pre>Hello $A!</pre> | A | <pre>A=$B...
>
> Alexey Semenyuk has updated the pull request incrementally with two
> additional commits since the last revision:
>
> - Merge branch 'JDK-8341641-master' of
> https://github.com/alexeysemenyukoracle/jdk into JDK-8341641-master
> - Formatting fixed
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.
-------------
PR Comment: https://git.openjdk.org/jdk/pull/23923#issuecomment-2704734396
