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//! Askama implements a type-safe compiler for Jinja-like templates. //! It lets you write templates in a Jinja-like syntax, //! which are linked to a `struct` defining the template context. //! This is done using a custom derive implementation (implemented //! in [`askama_derive`](https://crates.io/crates/askama_derive)). //! //! For feature highlights and a quick start, please review the //! [README](https://github.com/djc/askama/blob/master/README.md). //! //! # Creating Askama templates //! //! An Askama template is a `struct` definition which provides the template //! context combined with a UTF-8 encoded text file (or inline source, see //! below). Askama can be used to generate any kind of text-based format. //! The template file's extension may can be used to provide content type hints. //! //! A template consists of **text contents**, which are passed through as-is, //! **expressions**, which get replaced with content while being rendered, and //! **tags**, which control the template's logic. //! The template syntax is very similar to [Jinja](http://jinja.pocoo.org/), //! as well as Jinja-derivatives like [Twig](http://twig.sensiolabs.org/) or //! [Tera](https://github.com/Keats/tera). //! //! ## The `template()` attribute //! //! Askama works by generating one or more trait implementations for any //! `struct` type decorated with the `#[derive(Template)]` attribute. The //! code generation process takes some options that can be specified through //! the `template()` attribute. The following sub-attributes are currently //! recognized: //! //! * `path` (as `path = "foo.html"`): sets the path to the template file. The //! path is interpreted as relative to the `templates` dir in the directory //! where the originating crate's `Cargo.toml` resides. The file name //! extension is used to infer an escape mode (see below). In web framework //! integrations, the path's extension may also be used to infer the content //! type of the resulting response. Cannot be used together with `source`. //! * `source` (as `source = "{{ foo }}"`): directly sets the template source. //! This can be useful for test cases or short templates. The generated path //! is empty, which generally makes it impossible to refer to this template //! from other templates. Cannot be used together with `path`. //! * `ext` (as `ext = "txt"`): lets you specify the content type as a file //! extension. This is used to infer an escape mode (see below), and some //! web framework integrations use it to determine the content type. //! Cannot be used together with `path`. //! * `print` (as `print = "code"`): enable debugging by printing nothing //! (`none`), the parsed syntax tree (`ast`), the generated code (`code`) //! or `all` for both. The requested data will be printed to stdout at //! compile time. //! * `escape` (as `escape = "none"`): change escape mode for expression //! output. By default, Askama infers the escape mode from the template //! file name (with `path`) or specified extension (`ext`): if the extension //! is `html`, `htm` or `xml`, the `html` escape mode is used; otherwise, //! no implicit escaping is done. The escape mode can be overridden by //! specifying it manually, enabling it with `escape = "html"` or disabling //! with `escape = "none"`. The `html` escape mode escapes content according //! to the [OWASP escaping recommendations][owasp]. //! //! [owasp]: https://www.owasp.org/index.php/XSS_(Cross_Site_Scripting)_Prevention_Cheat_Sheet#RULE_.231_-_HTML_Escape_Before_Inserting_Untrusted_Data_into_HTML_Element_Content //! //! //! ## Variables //! //! Top-level template variables are defined by the template's context type. //! You can use a dot (`.`) to access variable's attributes or methods. //! Reading from variables is subject to the usual borrowing policies. //! For example, `{{ name }}` will get the ``name`` field from the template //! context, //! while `{{ user.name }}` will get the ``name`` field of the ``user`` //! field from the template context. //! //! ## Filters //! //! Values such as those obtained from variables can be post-processed //! using **filters**. //! Filters are applied to values using the pipe symbol (`|`) and may //! have optional extra arguments in parentheses. //! Filters can be chained, in which case the output from one filter //! is passed to the next. //! //! For example, `{{ "{:?}"|format(name|escape) }}` will escape HTML //! characters from the value obtained by accessing the `name` field, //! and print the resulting string as a Rust literal. //! //! Consult the [filters module documentation](filters/index.html) for a list //! of available filters. //! //! ## Whitespace control //! //! Askama preserves all whitespace in template code by default, //! except that a single trailing newline characters are suppressed. //! However, whitespace before and after expression and block delimiters //! can be suppressed by writing a minus sign directly following a //! start delimiter or leading into an end delimiter. //! Askama considers all tabs, spaces, newlines and carriage returns to be //! whitespace. //! //! ## Template inheritance //! //! Template inheritance allows you to build a base template with common //! elements that can then be shared by all inheriting templates. //! A base template defines **blocks** that child templates can then override. //! //! ### Base template //! //! ```text //! <!DOCTYPE html> //! <html lang="en"> //! <head> //! <title>{{ block title %}{{ title }}{% endblock %} - My Site</title> //! {% block head %}{% endblock %} //! </head> //! <body> //! <div id="content"> //! {% block content %}{% endblock %} //! </div> //! </body> //! </html> //! ``` //! //! The `block` tags define three blocks that can be filled in by child //! templates. The base template defines a default version of the block. //! A base template must define one or more blocks in order to be enable //! inheritance. Blocks can only be specified at the top level of a template, //! not inside `if`/`else` branches or in `for`-loop bodies. //! //! ### Child template //! //! Here's an example child template: //! //! ```text //! {% extends "base.html" %} //! //! {% block title %}Index{% endblock %} //! //! {% block head %} //! <style> //! </style> //! {% endblock %} //! //! {% block content %} //! <h1>Index</h1> //! <p>Hello, world!</p> //! {% endblock %} //! ``` //! //! The `extends` tag tells the code generator that this template inherits //! from another template. It will search for the base template relative to //! itself before looking relative to the template base directory. It will //! render the top-level content from the base template, and substitute //! blocks from the base template with those from the child template. The //! inheriting template context `struct` must have a field called `_parent` of //! the type used as the base template context. Blocks can refer to the context //! of both parent and child template. //! //! Note that, if the base template lives in another module than the child //! template, the child template's module should import all symbols from the //! base template's module in order for it to find the trait definition that //! supports the inheritance mechanism. //! //! ## HTML escaping //! //! Askama does not yet support automatic escaping. Care must be taken to //! escape content that may contain HTML control characters. You can use //! the `escape` filter (or its `e` alias) to escape data for use in HTML. //! //! ## Control structures //! //! ### For //! //! Loop over each item in an iterator. For example: //! //! ```text //! <h1>Users</h1> //! <ul> //! {% for user in users %} //! <li>{{ user.name|e }}</li> //! {% endfor %} //! </ul> //! ``` //! //! Inside for-loop blocks, some useful variables are accessible: //! //! * *loop.index*: current loop iteration (starting from 1) //! * *loop.index0*: current loop iteration (starting from 0) //! //! ### If //! //! The *if* statement is used as you might expect: //! //! ```text //! {% if users.len() == 0 %} //! No users //! {% else if users.len() == 1 %} //! 1 user //! {% else %} //! {{ users.len() }} users //! {% endif %} //! ``` //! //! ### Include //! //! The *include* statement lets you split large or repetitive blocks into //! separate template files. Included templates get full access to the context //! in which they're used, including local variables like those from loops: //! //! ```text //! {% for i in iter %} //! {% include "item.html" %} //! {% endfor %} //! ``` //! //! ```text //! * Item: {{ i }} //! ``` //! //! The path to include must be a string literal, so that it is known at //! compile time. Askama will try to find the specified template relative //! to the including template's path before falling back to the absolute //! template path. Use `include` within the branches of an `if`/`else` //! block to use includes more dynamically. //! //! ## Expressions //! //! Askama supports string literals (`"foo"`) and integer literals (`1`). //! It supports almost all binary operators that Rust supports, //! including arithmetic, comparison and logic operators. //! The parser applies the same precedence order as the Rust compiler. //! Expressions can be grouped using parentheses. //! The HTML special characters `&`, `<` and `>` will be replaced with their //! character entities unless the `escape` mode is disabled for a template. //! //! # Optional functionality //! //! ## Rocket integration //! //! Enabling the `with-rocket` feature appends an implementation of Rocket's //! `Responder` trait for each template type. This makes it easy to trivially //! return a value of that type in a Rocket handler. See //! [the example](https://github.com/djc/askama/blob/master/testing/tests/rocket.rs) //! from the Askama test suite for more on how to integrate. //! //! In case a run-time error occurs during templating, a `500 Internal Server //! Error` `Status` value will be returned, so that this can be further //! handled by your error catcher. //! //! ## Iron integration //! //! Enabling the `with-iron` feature appends an implementation of Iron's //! `Modifier<Response>` trait for each template type. This makes it easy to //! trivially return a value of that type in an Iron handler. See //! [the example](https://github.com/djc/askama/blob/master/testing/tests/iron.rs) //! from the Askama test suite for more on how to integrate. //! //! Note that Askama's generated `Modifier<Response>` implementation currently //! unwraps any run-time errors from the template. If you have a better //! suggestion, please [file an issue](https://github.com/djc/askama/issues/new). //! //! ## The `json` filter //! //! Enabling the `serde-json` filter will enable the use of the `json` filter. //! This will output formatted JSON for any value that implements the required //! `Serialize` trait. #![allow(unused_imports)] #[macro_use] extern crate askama_derive; extern crate askama_shared as shared; use shared::path; use std::fs::{self, DirEntry}; use std::io; use std::path::Path; /// Main `Template` trait; implementations are generally derived pub trait Template { /// Renders the template to the given `writer` buffer fn render_into(&self, writer: &mut std::fmt::Write) -> Result<()>; /// Helper method which allocates a new `String` and renders into it fn render(&self) -> Result<String> { let mut buf = String::new(); self.render_into(&mut buf)?; Ok(buf) } } pub use shared::filters; pub use askama_derive::*; pub use shared::{Error, MarkupDisplay, Result}; #[cfg(feature = "with-iron")] pub mod iron { extern crate iron; pub use self::iron::modifier::Modifier; pub use self::iron::response::Response; } #[cfg(feature = "with-rocket")] pub mod rocket { extern crate rocket; use self::rocket::http::{ContentType, Status}; use self::rocket::request::Request; use self::rocket::response::Response; use std::io::Cursor; pub use self::rocket::response::{Responder, Result}; pub fn respond(t: &super::Template, ext: &str) -> Result { let rsp = t.render().map_err(|_| Status::InternalServerError)?; let ctype = ContentType::from_extension(ext).ok_or(Status::InternalServerError)?; Response::build() .header(ctype) .sized_body(Cursor::new(rsp)) .ok() } } fn visit_dirs(dir: &Path, cb: &Fn(&DirEntry)) -> io::Result<()> { if dir.is_dir() { for entry in try!(fs::read_dir(dir)) { let entry = try!(entry); let path = entry.path(); if path.is_dir() { try!(visit_dirs(&path, cb)); } else { cb(&entry); } } } Ok(()) } /// Build script helper to rebuild crates if contained templates have changed /// /// Iterates over all files in the template dir (`templates` in /// `CARGO_MANIFEST_DIR`) and writes a `cargo:rerun-if-changed=` line for each /// of them to stdout. /// /// This helper method can be used in build scripts (`build.rs`) in crates /// that have templates, to make sure the crate gets rebuilt when template /// source code changes. pub fn rerun_if_templates_changed() { visit_dirs(&path::template_dir(), &|e: &DirEntry| { println!("cargo:rerun-if-changed={}", e.path().to_str().unwrap()); }).unwrap(); }