Variables in singly quoted LABEL values should be ignored

[rcjsuen]

Variables that are referred in singly quoted LABEL values are having features enabled for them when they shouldn't be. For example, selecting it will cause other instances to be highlighted and hovering over it will display a value even though the actual label in the built Docker image uses the raw string instead of the variable's expanded value. Similarly, textDocument/definition requests will be honoured to jump to the variable's definition even though it shouldn't actually be identified as a variable.

FROM scratch
ARG arg="a"
ENV var="value"
ENV var2='value2'
LABEL a=$var b="$var" c='$var'
LABEL d=$var2 e="$var2" f='$var2'
LABEL g=$arg h="$arg" i='$arg'

"Labels": {
	"a": "value",
	"b": "value",
	"c": "$var",
	"d": "value2",
	"e": "value2",
	"f": "$var2",
	"g": "a",
	"h": "a",
	"i": "$arg"
}