Don't even write newline when given no input with -xml

[jidanni]

$ tidy -q -xml /dev/null|od -c
0000000  \n
0000001

Please don't even write that. That way one can use test -s
to see if there was any output.

$ ... | tidy -q -xml > file.xml ; test -s file.xml && echo Hurray

[geoffmcl]

@jidanni thanks for the report...

Not really sure of the use case here, with a null input, but...

Hmmm, yes, in unix, with -xml, I can repeat that newline output, if given a null xml input, file or device...

Unfortunately, could not immediately repeat it in windows... file input is done through memory mapping the open file, but it seems this mapping fails, in CreateFileMapping(), if the file is of zero bytes...

But with a in file of just 1 tab character, which also generates no xml output, in Debug, I can see where the newline is generated... some code comments dropped for brevity...

    if ( showMarkup && (doc->errors == 0 || forceOutput) )
    {
        /* Output a Byte Order Mark if required */
        if ( outputBOM || (doc->inputHadBOM && smartBOM) )
            TY_(outBOM)( out );
            
        /* comment skipped */
        
        doc->docOut = out;
        if ( xmlOut && !xhtmlOut )
            TY_(PPrintXMLTree)( doc, NORMAL, 0, &doc->root );
        else if ( showBodyOnly( doc, bodyOnly ) )
            TY_(PrintBody)( doc );
        else
            TY_(PPrintTree)( doc, NORMAL, 0, &doc->root );

        TY_(PFlushLine)( doc, 0 );
        doc->docOut = NULL;
    }

That final TY_(PFlushLine)( doc, 0 ); will send a newline, to stdout/outfile, everytime, regardless of any previous output, or none...

Yes, in this xml case, that could be stopped by the same if logic above - if ( xmlOut && !xhtmlOut ) - ie moving it around... that would fix the -xml case...

But is that the complete solution? Maybe it is? There should always be a DOCTYPE for [x]html... but what about an empty body... hmmm...

On the otherhand, PFlushLine is in two parts...

    if ( pprint->linelen > 0 )
        PFlushLineImpl( doc );

    TY_(WriteChar)( '\n', doc->docOut );
    pprint->line++;

And then there is PCondFlushLine, which combines them - and only if there is queued stuff to go, then also send a newline...

    if ( pprint->linelen > 0 )
    {
         PFlushLineImpl( doc );

         TY_(WriteChar)( '\n', doc->docOut );
         pprint->line++;
    }

Maybe changing the PFlushLine to a PCondFlushLine would do the correct job for all cases...

Will continue testing... but look forward to further feedback... thanks...