Add optional caching

markup-proc-macro/Cargo.toml

@@ -16,3 +16,9 @@ proc-macro = true
 proc-macro2 = "1.0.3"
 quote = "1.0.2"
 syn = { version = "1.0.5", features = ["extra-traits", "full"] }
+sha2 = { version = "0.8", optional = true }
+dirs = { version = "2.0.2", optional = true }
+version = { version = "3.0.0", optional = true }
+
+[features]
+caching = ["sha2", "dirs", "version"]

markup-proc-macro/src/caching.rs

@@ -0,0 +1,35 @@
+use proc_macro::TokenStream;
+
+#[cfg(not(feature = "caching"))]
+pub fn cached(tokens: TokenStream, f: impl FnOnce(TokenStream) -> TokenStream) -> TokenStream {
+    f(tokens)
+}
+
+#[cfg(feature = "caching")]
+pub fn cached(tokens: TokenStream, f: impl FnOnce(TokenStream) -> TokenStream) -> TokenStream {
+    use sha2::{Digest, Sha256};
+    use std::fs;
+
+    let dir = dirs::cache_dir().unwrap().join("markup-rs");
+    let _ = fs::create_dir(&dir);
+    let dir = dir.join(version::version!().to_string());
+    let _ = fs::create_dir(&dir);
+
+    let input = tokens.to_string();
+    let mut hasher = Sha256::new();
+    hasher.input(input);
+    let hash = hasher.result();
+    let path = dir.join(format!("{:x}", hash));
+
+    if let Ok(cached) = fs::read_to_string(&path) {
+        if let Ok(cached) = cached.parse() {
+            return cached;
+        }
+    }
+
+    let output = f(tokens);
+    if fs::write(&path, output.to_string()).is_err() {
+        eprintln!("warning: cannot write to cache dir");
+    }
+    output
+}

markup-proc-macro/src/lib.rs

@@ -2,11 +2,16 @@
 extern crate proc_macro;
 
 mod ast;
+mod caching;
 mod generate;
 mod parse;
 
+use proc_macro::TokenStream;
+
 #[proc_macro]
-pub fn define(tokens: proc_macro::TokenStream) -> proc_macro::TokenStream {
-    let structs = syn::parse_macro_input!(tokens as parse::Many<ast::Struct>).0;
-    quote::quote!( #(#structs)* ).into()
+pub fn define(tokens: TokenStream) -> TokenStream {
+    caching::cached(tokens, |tokens| {
+        let structs = syn::parse_macro_input!(tokens as parse::Many<ast::Struct>).0;
+        quote::quote!( #(#structs)* ).into()
+    })
 }

markup/Cargo.toml

@@ -14,3 +14,6 @@ categories = ["template-engine"]
 
 [dependencies]
 markup-proc-macro = { path = "../markup-proc-macro", version = "0.4.0" }
+
+[features]
+caching = ["markup-proc-macro/caching"]