On Apr 7, 3:27 am, Arthur Clune <art...@clune.org> wrote: > On Thu, Apr 7, 2011 at 5:26 AM, Ben Hughes <b...@puppetlabs.com> wrote: > > I tried to recreate this, but your mailer has munged all the lines to fit > > in 80 columns, so I can't tell where all the breaks should be, so can't > > test it. Could you pastie or similar it? > > Thanks for looking at this. I've put it up at gist > > https://gist.github.com/907330 > > I've tried various variations on the line layout but all seem to give > the same result: if the name isn't defined, I get a blank line rather > than no line at all.
I haven't done much with ERB, but I used to work a lot with JSP, to which ERB seems very similar. In what follows, I take the somewhat risky approach of projecting JSP semantics onto ERB, so do take it with several grains of salt. I'm sure those more knowledgable about ERB itself will jump in where I err. 1. It is important to understand what the ERB processor is going to do with your template, which is basically to turn it inside out to yield a piece of executable Ruby code. Everything inside the ERB tags goes into the output as Ruby code (decorated, in the case of <%= %>), and everything outside gets turned into string literals and Ruby code to output them. 2. "Everything outside" the ERB tags includes literal newlines in your template, so normally those are echoed when the template is processed, subject to the Ruby control flow. This, I believe, is the basis for the comments I see in some ERB tutorials to the effect that "the standard <% %> tag pair will result in a newline being added to the output." I think that's incorrect. Reading the docs of the ERB class, I think it's actually a <% %> pair *followed by a newline* that results in a newline being added to the output -- and then only because the newline is present in the template. 3. ERB has a "trim mode" option, which in ERB dialects such as Rails' and Puppet's is enabled on a per-tag basis via the closing tag "-%>". Some describe trim mode simplistically as suppressing "the added newline", but ERB doesn't add a newline in the first place! The ERB docs themselves say something subtly different: "omit newline for lines ending in %>". In trim mode, then, ERB *modifies your template text* by removing certain newlines. 4. So the $64,000 question is this: which newlines will be removed from your template text? In particular, why weren't newlines removed where you expected? I strongly suspect that a close, literal reading of the ERB docs yields the answer. The newline is suppressed for lines *ending in* "%>", but not, one might interpret, for lines that have anything between the closing tag and the terminating newline. Say, for example, space characters. Check for trailing spaces in your template. Regards, John -- You received this message because you are subscribed to the Google Groups "Puppet Users" group. To post to this group, send email to puppet-users@googlegroups.com. To unsubscribe from this group, send email to puppet-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/puppet-users?hl=en.
