1 files changed, 64 insertions, 0 deletions
diff --git a/dhall_generated_parser/build.rs b/dhall_generated_parser/build.rs
new file mode 100644
index 0000000..615a55c
--- /dev/null
+++ b/dhall_generated_parser/build.rs
@@ -0,0 +1,64 @@
+use std::env;
+use std::fs::File;
+use std::io::{BufRead, BufReader, Read, Write};
+use std::path::Path;
+
+use abnf_to_pest::render_rules_to_pest;
+
+fn main() -> std::io::Result<()> {
+    // TODO: upstream changes to grammar
+    // let abnf_path = "../dhall-lang/standard/dhall.abnf";
+    let abnf_path = "src/dhall.abnf";
+    let visibility_path = "src/dhall.pest.visibility";
+    let pest_path = "src/dhall.pest";
+    println!("cargo:rerun-if-changed={}", abnf_path);
+    println!("cargo:rerun-if-changed={}", visibility_path);
+
+    let mut file = File::open(abnf_path)?;
+    let mut data = Vec::new();
+    file.read_to_end(&mut data)?;
+    data.push('\n' as u8);
+
+    let mut rules = abnf_to_pest::parse_abnf(&data)?;
+    for line in BufReader::new(File::open(visibility_path)?).lines() {
+        let line = line?;
+        if line.len() >= 2 && &line[0..2] == "# " {
+            rules.get_mut(&line[2..]).map(|x| x.silent = true);
+        }
+    }
+    rules.remove("simple_label");
+
+    let mut file = File::create(pest_path)?;
+    writeln!(&mut file, "// AUTO-GENERATED FILE. See build.rs.")?;
+    writeln!(&mut file, "{}", render_rules_to_pest(rules).pretty(80))?;
+
+    writeln!(&mut file)?;
+    writeln!(
+        &mut file,
+        "simple_label = {{
+              keyword ~ simple_label_next_char+
+            | !keyword ~ simple_label_first_char ~ simple_label_next_char*
+    }}"
+    )?;
+    writeln!(
+        &mut file,
+        "final_expression = ${{ SOI ~ complete_expression ~ EOI }}"
+    )?;
+
+    // Generate pest parser manually to avoid spurious recompilations
+    let derived = {
+        let pest_path = "dhall.pest";
+        let pest = quote::quote! {
+            #[grammar = #pest_path]
+            pub struct DhallParser;
+        };
+        pest_generator::derive_parser(pest, false)
+    };
+
+    let out_dir = env::var("OUT_DIR").unwrap();
+    let grammar_path = Path::new(&out_dir).join("grammar.rs");
+    let mut file = File::create(grammar_path)?;
+    writeln!(file, "pub struct DhallParser;\n{}", derived,)?;
+
+    Ok(())
+}