How do I get a snippet to insert a character only if the user typed something?

I have this snippet.

SELECT 'SELECT * FROM ' + OBJECT_SCHEMA_NAME(o.object_id, DB_ID(${20:})) + '.' + name,
       *
FROM ${20/$/./}sys.all_objects o
WHERE name LIKE '%${10:hadr}%'
ORDER BY o.name;

And this is how it works:

When the user types something in the function DB_ID(), I hope the content the user typed appears before sys.all_objects AND append an additional .. It already works like this as it shown in the above gif. However, I also hope if the user types nothing in the function DB_ID(), don’t add . before sys.all_objects. Is this possible?

>Solution :

You can use lookbehind to assert that there’s something in that field: (?<=.)$. For a minimal example, let’s say this is the original snippet:

foo($1); ${1/$/./}bar()

Change it to:

foo($1); ${1/(?<=.)$/./}bar()

If I type something, e.g. x, then press Tab, I get:

foo(x); x.bar()

If I don’t type anything then press Tab, I get:

foo(); bar()