1 files changed, 96 insertions, 2 deletions

diff --git a/dhall/build.rs b/dhall/build.rs
index a0106de..50f423e 100644
--- a/dhall/build.rs
+++ b/dhall/build.rs
@@ -1,10 +1,12 @@
 use std::env;
 use std::ffi::OsString;
 use std::fs::File;
-use std::io::Write;
+use std::io::{BufRead, BufReader, Read, Write};
 use std::path::{Path, PathBuf};
 use walkdir::WalkDir;
 
+use abnf_to_pest::render_rules_to_pest;
+
 #[derive(Debug, Clone, Copy)]
 enum FileType {
     Text,
@@ -100,7 +102,7 @@ fn make_test_module(
     Ok(())
 }
 
-fn main() -> std::io::Result<()> {
+fn generate_tests() -> std::io::Result<()> {
     // Tries to detect when the submodule gets updated.
     // To force regeneration of the test list, just `touch dhall-lang/.git`
     println!("cargo:rerun-if-changed=../dhall-lang/.git");
@@ -404,3 +406,95 @@ fn main() -> std::io::Result<()> {
 
     Ok(())
 }
+
+fn convert_abnf_to_pest() -> std::io::Result<()> {
+    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);
+        }
+    }
+
+    let mut file = File::create(pest_path)?;
+    writeln!(&mut file, "// AUTO-GENERATED FILE. See build.rs.")?;
+
+    // TODO: this is a cheat; properly support RFC3986 URLs instead
+    rules.remove("url_path");
+    writeln!(&mut file, "url_path = _{{ path }}")?;
+
+    rules.remove("simple_label");
+    writeln!(
+        &mut file,
+        "simple_label = {{
+              keyword ~ simple_label_next_char+
+            | !keyword ~ simple_label_first_char ~ simple_label_next_char*
+    }}"
+    )?;
+
+    rules.remove("nonreserved_label");
+    writeln!(
+        &mut file,
+        "nonreserved_label = _{{
+            !(builtin ~ !simple_label_next_char) ~ label
+    }}"
+    )?;
+
+    // Setup grammar for precedence climbing
+    rules.remove("operator_expression");
+    writeln!(&mut file, r##"
+        import_alt = {{ "?" ~ whsp1 }}
+        bool_or = {{ "||" }}
+        natural_plus = {{ "+" ~ whsp1 }}
+        text_append = {{ "++" }}
+        list_append = {{ "#" }}
+        bool_and = {{ "&&" }}
+        natural_times = {{ "*" }}
+        bool_eq = {{ "==" }}
+        bool_ne = {{ "!=" }}
+
+        operator = _{{
+            equivalent |
+            bool_ne |
+            bool_eq |
+            natural_times |
+            combine_types |
+            prefer |
+            combine |
+            bool_and |
+            list_append |
+            text_append |
+            natural_plus |
+            bool_or |
+            import_alt
+        }}
+        operator_expression = {{ application_expression ~ (whsp ~ operator ~ whsp ~ application_expression)* }}
+    "##)?;
+
+    writeln!(
+        &mut file,
+        "final_expression = ${{ SOI ~ complete_expression ~ EOI }}"
+    )?;
+
+    writeln!(&mut file)?;
+    writeln!(&mut file, "{}", render_rules_to_pest(rules).pretty(80))?;
+
+    Ok(())
+}
+
+fn main() -> std::io::Result<()> {
+    convert_abnf_to_pest()?;
+    generate_tests()?;
+    Ok(())
+}