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View Code? Open in Web Editor NEWErlang port of Haml
Home Page: http://weblog.hypotheticalabs.com
Erlang port of Haml
Home Page: http://weblog.hypotheticalabs.com
Welcome to herml, the Haml-like templating language! Building: 1) Install leex 0.3 or greater. Putting it in your $ERLANG_HOME/lib is best. leex is included with R13B01. 2) Clone the herml repo from Github. 3) Run make 4) Put the herml/ebin directory somewhere on your code path: 4a) Symlink the top-level herml directory into your $ERLANG_HOME/lib directory -or- 4b) Use the -pz or -pa switches on erl to place herml/ebin onto your code path Using in Sinan: 1) Clone the herml repo from Github 2) Run `make special` in the herml directory 3) Make sure your sinan project can find the herml repo 3a) Clone inside your projects lib directory -or- 3b) Symlink the herml directory to your projects lib directory 4) Keep it up to date: a) Pull down latest changes b) `make clean` c) `make special` Running tests: 1) Run make clean tests Using herml: 1) Start up a herml_manager process for your template directory: 1> herml_manager:start_link(my_web_app,"/path/to/templates"). Note: herml_manager can cache the compiled template and use it over and over. 2) Execute the template by calling the herml_manager process: 2> Result = herml_manager:execute_template("file.herml", Env). Note: Env is a proplist containing the execution environment for the template. herml expects all variable names to be Erlang strings. For example, here's a valid environment proplists: [{"UserName", "herml"}]. The UserName variable would be referenced from herml as @UserName. Another note: For efficiency reasons, herml_manager:execute_template/2,3,4 returns iolists when it executes templates. If you want to view the template output as a standard string, you can use the io module to flatten the iolist: 3> io:format("~s", [Result]).
Hi, nice stuff!
However I noticed that it fails to parse some common hamls:
%h1 Some title
or
%p
nice
%span Chicken Fried
The Leex is included in Erlang R13B01 does not work with outdir option.
To make Herml work for this Erlang version, Makefile should be changed to:
leex:file("src/herml_scan.xrl")
I've found Herml (tested on 2942bd1) to hang in parser-generated code on the following template:
!!!
%html
%head
%meta[{charset,"utf-8"}]/
Generated parser continued to recursively call itself herml_scan:string/4
in an endless loop, quickly hogging all memory. Unfortunately, I'm too newbie to Erlang and leex, so I don't really understand why this happens. Anyway, the calls are occurring in this way:
...
string/4(",\"utf-8\"}]/", 1, ",\"utf-8\"}]/", [{chr,1,"charset"},{lcurly,1,[123]},{lbrace,1,[91]},{chr,1,[109,101,116,97]},{tag_start,1,[37]}])
string/4("\"utf-8\"}]/", 1, "\"utf-8\"}]/", [{comma,1,[44]},{chr,1,"charset"},{lcurly,1,[123]},{lbrace,1,[91]},{chr,1,[109,101,116,97]},{tag_start,1,[37]}])
string/4("\"utf-8\"}]/", 1, "\"utf-8\"}]/", [{pipe,1,[]},{comma,1,[44]},{chr,1,"charset"},{lcurly,1,[123]},{lbrace,1,[91]},{chr,1,[109,101,116,97]},{tag_start,1,[37]}])
string/4("\"utf-8\"}]/", 1, "\"utf-8\"}]/", [{pipe,1,[]},{pipe,1,[]},{comma,1,[44]},{chr,1,"charset"},{lcurly,1,[123]},{lbrace,1,[91]},{chr,1,[109,101,116,97]},{tag_start,1,[37]}])
string/4("\"utf-8\"}]/", 1, "\"utf-8\"}]/", [{pipe,1,[]},{pipe,1,[]},{pipe,1,[]},{comma,1,[44]},{chr,1,"charset"},{lcurly,1,[123]},{lbrace,1,[91]},{chr,1,[109,101,116,97]},{tag_start,1,[37]}])
string/4("\"utf-8\"}]/", 1, "\"utf-8\"}]/", [{pipe,1,[]},{pipe,1,[]},{pipe,1,[]},{pipe,1,[]},{comma,1,[44]},{chr,1,"charset"},{lcurly,1,[123]},{lbrace,1,[91]},{chr,1,[109,101,116,97]},{tag_start,1,[37]}])
...
There are certainly no "|" characters in template, and I really don't know why {pipe,1,[]}
is there.
After some mindless fiddling, I've found that similiar hangs happen on intentionally malformed %meta[{charset,"utf-8}]/
(missing second double quote) code, and when there are any "unknown" characters (for example, UTF-8 Cyrillic).
I've attempted to fix the issue with drdaeman/herml@58b4958, but due to a lack of expertise I don't know whenever this is the proper solution, or it just happen to work.
Although it spawns processes, I doubt that herml_manager may be a bottle neck.
I propose that a template be compiled to a module in-memory (the module name can be referred from the template path implicitly, or specified explicitly) with a function "render" so that it can render itself.
In other words, a template is converted into code instead of data. This way, the Erlang VM caches and manages the templates for us efficiently. When we want to render, just call it. When we want to update a template, just recompile it and the Erlang VM will automatically replace the old code with the new one for us.
For example, the library "erlang-gettext" can compile a plain text .po file to a module elegantly like this:
http://github.com/davide/erlang-gettext/blob/baee1560a705d1337fa05be822fde57abef1d312/src/gettext_generate.erl
For a feeling, ErlyDTL is working like this:
erlydtl:compile("/path/to/welcome.html", welcome_template),
welcome_template:render([
{name, "Johnny"},
{friends, [<<"Frankie Lee">>, <<"Judas Priest">>]},
{primes, [1, 2, "3", <<"5">>]}
]).
I'm new to AST. I found some instruction here:
http://www.evanmiller.org/write-a-template-compiler-for-erlang.html
In README:
render(CompiledTemplate, Env)
In source code:
render(Template, Offset) ->
render(Template, [], Offset).
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