templates cannot have default values containing new lines

[panzi]

The default value of a variable cannot contain a new line (\n) character because .* doesn't match those. I.e. if you have this in your .env file:

FOO="${BAR:-multi
line}"

You get this error mesage:

2024/07/02 02:49:54 Invalid template: "${BAR:-multi\nline}"

This is a bit confusing, because this doesn't look like an invalid template. Because of the quotes the whole string is correctly parsed, the template has a valid name and does end with }. To fix this you need to change this regular expression:

compose-go/template/template.go

Line 31 in 9d0d133

var substitutionBraced = "[_a-z][_a-z0-9]*(?::?[-+?](.*))?"

To this:

var substitutionBraced = "[_a-z][_a-z0-9]*(?::?[-+?]((?:.|\n)*))?"

(I don't know if there is another way to match anything, including a \n, in Go.)