Dictionary view ALL_SOURCE contains only several object types like PROCEDURE, PACKAGE BODY, FUNCTION, TYPE except VIEW. If you want to search some text for view definition, you should go for ALL_VIEWS.
But the thing is, the column TEXT in ALL_VIEWS is LONG which is a plain old text storing type, it cannot be searched.
SQL> conn hr/hr;
SQL> column owner format a10;
SQL> column view_name format a30;
SQL> select owner, view_name from all_views where upper(text) like '%NAME%' order by 1,2;
select owner, view_name from all_views where upper(text) like '%NAME%'
ERROR at line 1:
ORA-00932: inconsistent datatypes: expected CHAR got LONG
As you can see, we cannot use LIKE to filter the column value. There're more explanations about solving ORA-00932.
For 11g and earlier releases
The first idea in my mind is to convert TEXT into something searchable. Luckily we have CLOB which is a searchable column type. We can just convert LONG text into CLOB for further operations.
The solution is simple, create a table that contains some information you need by using Create Table As Select (CTAS).
SQL> create table all_views_searchable as select owner, view_name, to_lob(text) text from all_views;
In which, TO_LOB() function is the key to convert LONG text into CLOB. Now, we can search the new table instead of ALL_VIEWS with the same statement.
SQL> select owner, view_name from all_views_searchable where upper(text) like '%NAME%' order by 1,2;
For 12c and later releases
You don't bother doing that, a convenient column in ALL_VIEWS called TEXT_VC allows you to do some searches, which is derived and trimmed from TEXT. For example, ALL_VIEWS in release 19c.