<div dir="ltr">Yes, I like dynamic-rerequire. Because it already has the file-watching facility built in, I rely on it as a sort of sonar device to find out if a source file has changed, like so:<div> </div><div>(define (source-changed? source-path)</div> <div> </div><div><div> (define port-for-catching-file-info (open-output-string))</div><div> </div><div> (parameterize ([current-directory source-dir] </div><div> [current-error-port port-for-catching-file-info])</div> <div> (dynamic-rerequire source-path))</div><div> </div><div> ((length (get-output-string port-for-catching-file-info)) . > . 0))) </div></div></div><div class="gmail_extra"> <div class="gmail_quote">On Mon, Oct 14, 2013 at 12:31 PM, Matthew Flatt <<a href="mailto:mflatt@cs.utah.edu" target="_blank">mflatt@cs.utah.edu</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I think the advice that Robby gives is probably better, but... If you only need to pick up changes to a module (as opposed to running a module afresh for its side effects), and if you're using 5.90.x, you could try using `dynamic-rerequire` in a single namespace to reload modules. <div class="HOEnZb"><div class="h5"> At Mon, 14 Oct 2013 13:22:21 -0500, Robby Findler wrote: > Did you try using namespace-attach-module to attach 'racket and > 'web-server/templates? Something like: > > (define orig-ns (current-namespace)) > (parameterize ([current-namespace (make-base-empty-namespace)]) > (namespace-attach-module orig-ns 'racket) > (namespace-attach-module orig-ns 'web-server/templates) > (namespace-require 'racket) > (eval `(begin > (require web-server/templates) > (require ,my-source-path-string) > (include-template ,my-template-path-string)) > (current-namespace))) > > But 7 seconds seems remarkably long (I see a speed up of about 50% for that > function (with the my-source-path-string and my-template-path-string lines > commented out): from 250 to 170 msec). > > It may be that your .zo files or something are not up to date. So you may > want to stick a 'raco make' somewhere in there to avoid recompiling your > files every time and just recompile the ones that changed. > > Robby > > > > > On Mon, Oct 14, 2013 at 1:14 PM, Matthew Butterick > <<a href="mailto:mb.list.acct@gmail.com">mb.list.acct@gmail.com</a>>wrote: > > > At RacketCon I talked about my Pollen system for making web pages. Though > > I don't use the Racket webserver to provide live generation of web pages, I > > do use it to provide a kind of browser-assisted REPL for development. As I > > edit the project files, I want to reload the URL in the browser and see the > > changes (without restarting the webserver). > > > > Moreover, since it's a development tool, it wants to be maximally dynamic. > > For instance, I might be editing source files containing page content, or > > the design templates (which might also contain Racket code), or supporting > > Racket libraries (e.g., CSS generators). > > > > Jay has suggested that this can be done with eval. And indeed it can. > > Here's the quasicode I use: > > > > (parameterize ([current-namespace (make-base-empty-namespace)]) > > (namespace-require 'racket) > > (eval `(begin > > (require web-server/templates) > > (require ,my-source-path-string) > > (include-template ,my-template-path-string)) > > (current-namespace)))) > > > > This works great, with one wrinkle: it's the slowest operation in the > > whole system, taking about 7-8 secs to render each page. This is not a > > grave hardship, and certainly faster than restarting the web server. But > > I'd still be curious if I'm overlooking a better approach. > > > > In general, the render time is fairly consistent regardless of what's in > > the page, which suggests to me that most of the expense comes from setting > > up the fresh namespace. I did try making a namespace separately and reusing > > it, but that didn't work (code wouldn't get reloaded). Is there a way to > > "clean" a namespace that's cheaper than setting up a new one? > > > > Another option I considered is starting up another instance of Racket in a > > subprocess, but it would need to be made into a synchronous operation. Long > > drive for a short day at the beach, etc. > > > > It's also possible that I'm running up against the irreducible cost of > > high-quality eval, in which case, I will accept it and move on. > > > > > > Matthew Butterick > > > > > > > > > > On Thu, Jun 6, 2013 at 7:36 PM, Greg Hendershott < > > <a href="mailto:greghendershott@gmail.com">greghendershott@gmail.com</a>> wrote: > > > >> Great timing! It's been on my short list to make my static blog > >> generator more flexible. From > >> <a href="http://docs.racket-lang.org/web-server/templates.html" target="_blank">http://docs.racket-lang.org/web-server/templates.html</a> I got the idea > >> that it would be suitable only for static templates, but now I > >> understand that's not the case. Today I made a topic branch using this > >> approach that's working well, which I plan to merge after some testing > >> and polishing. > >> > >> p.s. Maybe it's obvious, but because `include-template` uses > >> `include-at/relative-to/reader`, it won't include a template if you > >> give it a full path. Maybe there's a more-elegant way, but I found it > >> worked to parameterize `current-directory` around the call to `eval`. > >> > >> > >> On Wed, Jun 5, 2013 at 4:45 PM, Jay McCarthy <<a href="mailto:jay.mccarthy@gmail.com">jay.mccarthy@gmail.com</a>> > >> wrote: > >> > While it is supposed to be pithy, it is also serious. > >> > > >> > When I wrote it, I imagine that people would do something like this: > >> > > >> > #lang racket/base > >> > (require web-server/templates) > >> > > >> > (define (template-content t x) > >> > (eval #`(let ([x #,x]) (include-template #,t)))) > >> > > >> > (template-content "t.txt" 5) > >> > (template-content "t.txt" 6) > >> > > >> > and trust that the template wouldn't include @(system "rm -fr /"). I > >> > think that a simple eval works just fine for when you, the programmer, > >> > want to change the content dynamic (although I'd say it is better to > >> > use the web-server language so you can restart with the same > >> > continuations, etc.) > >> > > >> > Your solution is great for a template that a user provides, although > >> > it has the hole that the template could call @include-template and > >> > maybe find itself and go into a infinite loop, so it's not totally > >> > "secure" unless you use a sandbox. > >> > > >> > Jay > >> > > >> > On Wed, Jun 5, 2013 at 1:53 PM, Joe Gibbs Politz <<a href="mailto:joe@cs.brown.edu">joe@cs.brown.edu</a>> > >> wrote: > >> >> I'm writing a web server in a #lang that doesn't support macros or > >> >> syntactic abstraction. I would like to be able to use some sort of > >> >> templating dynamically with bindings given by values, e.g. > >> >> > >> >> template.render("page-with-hole-for-username.html", { username: "Joe" > >> }) > >> >> > >> >> The FAQ ( > >> > <a href="http://docs.racket-lang.org/web-server/faq.html#(part._.How_do_.I_use_templates" target="_blank">http://docs.racket-lang.org/web-server/faq.html#(part._.How_do_.I_use_templates</a> > __dynamically__) > >> ) > >> >> in the documentation for templates ends with this pithy > >> >> recommendation: > >> >> > >> >> "If you insist on dynamicism, there is always eval." > >> >> > >> >> I assume this isn't intended seriously, and instead to discourage what > >> >> I'm asking about, but I'm unfortunately not seeing another way to > >> >> write my program. The code at the end of this message seems like the > >> >> best I can do while being relatively safe, but also like a dubious > >> >> inclusion on a web server given the eval. > >> >> > >> >> Is this the best I can hope for? Is there another collection I should > >> >> be looking into? Any other recommendations? > >> >> > >> >> Thanks! > >> >> Joe P. > >> >> > >> >> > >> >> #lang racket/base > >> >> > >> >> (require > >> >> web-server/templates) > >> >> > >> >> (define (render-template filename dict) > >> >> (define namespace-for-template (make-empty-namespace)) > >> >> (namespace-attach-module (current-namespace) 'web-server/templates > >> >> namespace-for-template) > >> >> (hash-map dict > >> >> (lambda (key value) > >> >> (define name-of-identifier (string->symbol key)) > >> >> (namespace-set-variable-value! > >> >> name-of-identifier > >> >> value > >> >> #f > >> >> namespace-for-template))) > >> >> (parameterize [(current-namespace namespace-for-template)] > >> >> (namespace-require 'web-server/templates)) > >> >> (define to-eval #`(include-template #,(datum->syntax > >> >> #'render-template filename))) > >> >> (eval to-eval namespace-for-template)) > >> >> ____________________ > >> >> Racket Users list: > >> >> <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a> > >> > > >> > > >> > > >> > -- > >> > Jay McCarthy <<a href="mailto:jay@cs.byu.edu">jay@cs.byu.edu</a>> > >> > Assistant Professor / Brigham Young University > >> > <a href="http://faculty.cs.byu.edu/~jay" target="_blank">http://faculty.cs.byu.edu/~jay</a> > >> > > >> > "The glory of God is Intelligence" - D&C 93 > >> > ____________________ > >> > Racket Users list: > >> > <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a> > >> ____________________ > >> Racket Users list: > >> <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a> > >> > > > > > > ____________________ > > Racket Users list: > > <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a> > > > > > ____________________ > Racket Users list: > <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a> </div></div></blockquote></div> </div>