1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
|
#[macro_use]
extern crate nom;
extern crate proc_macro;
extern crate quote;
extern crate syn;
use proc_macro::TokenStream;
mod generator;
mod parser;
mod path;
// Holds metadata for the template, based on the `template()` attribute.
struct TemplateMeta {
path: String,
print: String,
}
// 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(ast: &syn::DeriveInput) -> TemplateMeta {
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 path = None;
let mut print = "none".to_string();
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 {
path = Some(s.clone());
} else {
panic!("template path must be string literal");
},
"print" => if let syn::Lit::Str(ref s, _) = *val {
print = s.clone();
} else {
panic!("print value must be string literal");
},
_ => { panic!("unsupported annotation key found") }
}
}
}
}
}
if path.is_none() {
panic!("template path not found in struct attributes");
}
TemplateMeta { path: path.unwrap(), print: print }
}
/// 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 = path::find_template_from_path(&meta.path, None);
let src = path::get_template_source(&path);
let nodes = parser::parse(&src);
if meta.print == "ast" || meta.print == "all" {
println!("{:?}", nodes);
}
let code = generator::generate(ast, &meta.path, nodes);
if meta.print == "code" || meta.print == "all" {
println!("{}", code);
}
code
}
#[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()
}
|
