How to Match a Pattern within Another Match in Vim Syntax file -

i have custom config involves following syntax:

• key=value
• $(var) represents variable

the $(var) part can appear in both key , value, i.e. message="hello $(firsname) $(lastname)". value part must surrounded double quote " if contains space characters.

i want match key, value , $(var) , highlight them separately in vim.

here in vim syntax file:

syn match configvalue "\(\s\+=\)\@<=\"[^\"]*\"\|\(\s\+=\)\@<=\s\+" syn match configkey "^\s*[a-za-z0-9_.]\+\(\s*=\)\@=" syn match configvar "\$(.*)" 

the code matches configvalue , configkey, not configvar if within key=value. ruled syntax match priority (h:syn-priority):

1. when multiple match or region items start in same position, item defined last has priority.
2. a keyword has priority on match , region items.
3. an item starts in earlier position has priority on items start in later positions.

rule 3 gives other 2 matches higher priority of configvar.

my problem that, how match 3 patterns separately, configvar having highest priority?

to have configvar match inside configvalue, have contain it; done via contained (leave off if var can match anywhere, not inside key=value) , contains=... attributes:

syn match configvalue "\(\s\+=\)\@<=\"[^\"]*\"\|\(\s\+=\)\@<=\s\+" contains=configvar syn match configvar "\$([^)]*)" contained 

note i've changed pattern configvar avoid matching $(foo) , $(bar) one element.

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you said configvar can appear in configkey, that, range of allowed characters needs include $(), too. then, containment works well:

syn match configkey "^\s*[a-za-z0-9_.$()]\+\(\s*=\)\@=" contains=configvar