Unexpected MapCSS REGEX errors

[goodidea]

I'm currently working on a more complex custom MapCSS (for traffic signs – but that's not relevant here), that makes extensive use of selectors with REGEX (regular expressions).

But some REGEX expressions did not work – and there were error messages in the JAVA console that I couldn't explain at all. And I had previously tested the REGEX expressions extensively, e.g. on ​https://regex101.com/, where you can also set JAVA as a REGEX flavor, and they seemed to be valid and error-free. I also got the desired results with test strings.

And according to the JOSM documentation (see https://josm.openstreetmap.de/wiki/Help/Styles/MapCSSImplementation#Conditionselector) the REGEX flavor, which is supported by JOSM, is the one of JAVA 11 – at least that's what the documentation says (​https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/regex/Pattern.html#sum).

After a lot of testing, I found out that this is probably the case, but that some special characters and predefined character classes etc. cause an error in JOSM, namely these (and I especially wanted to use \h for whitespace characters – which I have now replaced with \s, which works in contrast to \h – see below):

\t
\n
\r
\R
\f
\a
\e
\h
\H
\v
\V
\Q
\E

If you use this in a MapCSS, you will get an error message like this in the JAVA Console:

2025-01-23 19:27:56.578 SEVERE: Skipping to the next rule, because of an error: org.openstreetmap.josm.gui.mappaint.mapcss.parsergen.ParseException: Encountered " "~" "~ "" at line 137, column 19.
Was expecting one of:
    "set" ...
    <IDENT> ...
    <UINT> ...
    <STRING> ...
    "(" ...
    <UFLOAT> ...
    <HEXCOLOR> ...
    <S> ...
    "=" ...
    "!" ...
    "+" ...
    "-" ...
    "/*" ...
    <S> ...
    "-" ...
    <UINT> ...
    "-" ...
    <UFLOAT> ...
    <UINT> ...
    <IDENT> ...
    "set" ...
    <STRING> ...
    <STRING> ...
    <STRING> ...
    <STRING> ...
    <STRING> ...
    <IDENT> ...
    "set" ...

These special characters, predefined character classes and boundary matchers, however, work without problems:

\d
\D
\s
\S
\w
\W
\b
\B
\A
\G
\z
\Z

Is this a bug in the MapCSS parser – or is the documentation of which REGEX expressions are supported “just” inadequate and should be clarified?

What steps will reproduce the problem?

Create a custom CSS with a rule like:

node[traffic_sign=~/^xxx\hxxx.*/] {
   text: auto;
}

... and add it to the JOSM map paint styles.

Additional system information:

Revision:19277
Build-Date:2025-01-04 02:30:34
URL:https://josm.openstreetmap.de/svn/trunk

Identification: JOSM/1.5 (19277 en) Mac OS X 10.14.6
OS Build number: Mac OS X 10.14.6 (18G9323)
Memory Usage: 998 MB / 4096 MB (453 MB allocated, but free)
Java version: 17.0.13+11-LTS, Azul Systems, Inc., OpenJDK 64-Bit Server VM
Look and Feel: com.apple.laf.AquaLookAndFeel

Last errors/warnings:

• 03265.734 E: Skipping to the next rule, because of an error: org.openstreetmap.josm.gui.mappaint.mapcss.parsergen.ParseException: Encountered " "~" "~ "" at line 137, column 19.

[stoecker]

Probably a bug. Characters missing in source:trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSParser.jj#L169​

[stoecker]

Thanks for that detailed report. Fix should be easy now for someone not using his mobile to check new bugcreports. 😀

[stoecker]

In 19288/josm:

add missing escape characters to mapcss parser, fix #24095

[goodidea]

Great! Thank you for the fast fix!!! I hope the next JOSM Version comes soon ...

[stoecker]

Simply use josm-latest. 😺

[goodidea]

josm-latest: thanks for the hint! I forgot, that it's easy to launch the latest build ... Haven't used it for a long time.

I first tried to start a JOSM jar of the 19290 build with the terminal in macOS (and had Azul JDK 17.0.14 installed!) – but not so easy, because it seems necessary to add further parameters like --add-exports=java.base/sun.security.action=ALL-UNNAMED and others. Then I found the right ones in the JNLPs and in the end it worked. But it took me some time to figure it out. The instructions on https://josm.openstreetmap.de/wiki/Download#Java didn't really help with everything. It worked with (not sure if ALL the parameters are necessary):

java --add-exports=java.base/sun.security.action=ALL-UNNAMED --add-exports=java.desktop/com.apple.eawt=ALL-UNNAMED --add-exports=java.desktop/com.sun.imageio.spi=ALL-UNNAMED --add-exports=java.desktop/com.sun.imageio.plugins.jpeg=ALL-UNNAMED --add-opens=java.base/java.lang=ALL-UNNAMED --add-opens=java.base/java.nio=ALL-UNNAMED --add-opens=java.base/jdk.internal.loader=ALL-UNNAMED --add-opens=java.base/jdk.internal.ref=ALL-UNNAMED --add-opens=java.desktop/javax.imageio.spi=ALL-UNNAMED --add-opens=java.desktop/javax.swing.text.html=ALL-UNNAMED --add-opens=java.prefs/java.util.prefs=ALL-UNNAMED -jar josm-latest.jar

But with the josm-latest.jnlp it's easier … and there is the nice JAVA console from OpenWebStart with coloured text ... But then I directly fell into the next trap: I ​​renamed it to JOSM latest Webstart (pre-release development version, not fully tested, with JAVA 11+).jnlp, which immediately caused an error with OpenWebStart because of the + character. Also took some time to find that out ... See ​https://github.com/karakun/OpenWebStart/issues/599. Bad luck – and always pitfalls with JAVA. But now I know what to look out for (and what I should not do).

And according to the roadmap, the next tested, stable version should come in some hours (milestone 25.01), if I understand correctly. Very nice!