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extern crate askama_shared as shared;
extern crate proc_macro;
extern crate syn;
use proc_macro::TokenStream;
use std::borrow::Cow;
use std::path::PathBuf;
#[proc_macro_derive(Template, attributes(template))]
pub fn derive_template(input: TokenStream) -> TokenStream {
let ast = syn::parse_derive_input(&input.to_string()).unwrap();
match ast.body {
syn::Body::Struct(ref data) => data,
_ => panic!("#[derive(Template)] can only be used with structs"),
};
build_template(&ast).parse().unwrap()
}
/// Takes a `syn::DeriveInput` and generates source code for it
///
/// Reads the metadata from the `template()` attribute to get the template
/// metadata, then fetches the source from the filesystem. The source is
/// parsed, and the parse tree is fed to the code generator. Will print
/// the parse tree and/or generated source according to the `print` key's
/// value as passed to the `template()` attribute.
fn build_template(ast: &syn::DeriveInput) -> String {
let meta = get_template_meta(ast);
let (path, src) = match meta.source {
Source::Source(s) => (PathBuf::new(), Cow::Borrowed(s)),
Source::Path(s) => {
let path = shared::path::find_template_from_path(&s, None);
let src = shared::path::get_template_source(&path);
(path, Cow::Owned(src))
},
};
let nodes = shared::parse(src.as_ref());
if meta.print == Print::Ast || meta.print == Print::All {
println!("{:?}", nodes);
}
let code = shared::generate(ast, &path, nodes);
if meta.print == Print::Code || meta.print == Print::All {
println!("{}", code);
}
code
}
// Returns a `TemplateMeta` based on the `template()` attribute data found
// in the parsed struct or enum. Will panic if it does not find the required
// template path, or if the `print` key has an unexpected value.
fn get_template_meta<'a>(ast: &'a syn::DeriveInput) -> TemplateMeta<'a> {
let attr = ast.attrs.iter().find(|a| a.name() == "template");
if attr.is_none() {
let msg = format!("'template' attribute not found on struct '{}'",
ast.ident.as_ref());
panic!(msg);
}
let attr = attr.unwrap();
let mut source = None;
let mut print = Print::None;
if let syn::MetaItem::List(_, ref inner) = attr.value {
for nm_item in inner {
if let syn::NestedMetaItem::MetaItem(ref item) = *nm_item {
if let syn::MetaItem::NameValue(ref key, ref val) = *item {
match key.as_ref() {
"path" => if let syn::Lit::Str(ref s, _) = *val {
source = Some(Source::Path(s.as_ref()));
} else {
panic!("template path must be string literal");
},
"source" => if let syn::Lit::Str(ref s, _) = *val {
source = Some(Source::Source(s.as_ref()));
} else {
panic!("template source must be string literal");
},
"print" => if let syn::Lit::Str(ref s, _) = *val {
print = s.into();
} else {
panic!("print value must be string literal");
},
_ => { panic!("unsupported annotation key found") }
}
}
}
}
}
match source {
Some(s) => TemplateMeta { source: s, print },
None => panic!("template path or source not found in struct attributes"),
}
}
// Holds metadata for the template, based on the `template()` attribute.
struct TemplateMeta<'a> {
source: Source<'a>,
print: Print,
}
enum Source<'a> {
Path(&'a str),
Source(&'a str),
}
#[derive(PartialEq)]
enum Print {
All,
Ast,
Code,
None,
}
impl<'a> From<&'a String> for Print {
fn from(s: &'a String) -> Print {
use Print::*;
match s.as_ref() {
"all" => All,
"ast" => Ast,
"code" => Code,
"none" => None,
v => panic!("invalid value for print option: {}", v),
}
}
}
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