On Wed, 5 Mar 2025 21:13:44 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</pre><pre>B=John</pre> | <pre>Hello
> $B</pre> | Variable "B" will ...
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!`?
-------------
PR Comment: https://git.openjdk.org/jdk/pull/23923#issuecomment-2702585129
