Get name of the parsed file? - antlr

Question

I would like to parse a file where the first line may or may not contain a definition of a "project" name (like with Pascal's program keyword), and if not, use the name of the file that is being parsed as default. Simplified:
#members{ String projectName; }
project : {projectName = ...} // name of parsed file as default
( PROJECTNAMEKEYWORD ID {projectName = $ID.text;} )?
otherstuff {/*...*/};
Is this even possible? I found this surprisingly hard to find out using google or the antlr manual. By its documentation, input.getSourceName() should be what I am looking for, but it always returns null, and debugging lead me to the class ANTLRStringStream that has a name field whose value is returned by this method but never set.

Answer 1

Simply create a custom constructor in your parser that takes a string that represents your file.
A demo:
grammar T;
#parser::members {
private String projectName;
public TParser(String fileName) throws java.io.IOException {
super(new CommonTokenStream(new TLexer(new ANTLRFileStream(fileName))));
projectName = fileName;
}
public String getProjectName() {
return projectName;
}
}
parse
: (PROJECT ID {projectName = $ID.text;})? EOF
;
PROJECT : 'project';
ID : ('a'..'z' | 'A'..'Z')+;
SPACE : (' ' | '\t' | '\r' | '\n') {skip();};
which can be tested with:
import org.antlr.runtime.*;
public class Main {
public static void main(String[] args) throws Exception {
// 'empty.txt' is, as the name suggests, an empty file
TParser parser = new TParser("empty.txt");
parser.parse();
System.out.println(parser.getProjectName());
// 'test.txt' contains a single line with the words: 'project JustATest'
parser = new TParser("test.txt");
parser.parse();
System.out.println(parser.getProjectName());
}
}
If you run the Main class, the following will be printed to your console:
empty.txt
JustATest