Improve testers ♻

1 files changed, 28 insertions, 13 deletions

diff --git a/build.rs b/build.rs
index c91db8e0..1254e33d 100644
--- a/build.rs
+++ b/build.rs
@@ -1,34 +1,49 @@
-use std::fs;
+use std::fs::{self, create_dir_all, read_dir, read_to_string};
 use std::ffi::OsStr;
 
-fn main() {
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    create_dir_all("tests/cache")?;
+
+    // Make sure the script reruns if this file changes or files are
+    // added/deleted in the parsing folder.
     println!("cargo:rerun-if-changed=build.rs");
     println!("cargo:rerun-if-changed=tests/parsing");
 
-    fs::create_dir_all("tests/cache").unwrap();
+    // Compile all parser tests into a single giant vector.
+    let mut code = "vec![".to_string();
 
-    let paths = fs::read_dir("tests/parsing").unwrap()
-        .map(|entry| entry.unwrap().path())
-        .filter(|path| path.extension() == Some(OsStr::new("rs")));
+    for entry in read_dir("tests/parsing")? {
+        let path = entry?.path();
+        if path.extension() != Some(OsStr::new("rs")) {
+            continue;
+        }
 
-    let mut code = "vec![".to_string();
-    for path in paths {
-        let name = path.file_stem().unwrap().to_str().unwrap();
-        let file = fs::read_to_string(&path).unwrap();
+        let name = path
+            .file_stem().ok_or("expected file stem")?
+            .to_string_lossy();
 
+        // Make sure this also reruns if the contents of a file in parsing
+        // change. This is not ensured by rerunning only on the folder.
         println!("cargo:rerun-if-changed=tests/parsing/{}.rs", name);
 
         code.push_str(&format!("(\"{}\", tokens!{{", name));
 
+        // Replace the `=>` arrows with a double arrow indicating the line
+        // number in the middle, such that the tester can tell which line number
+        // a test originated from.
+        let file = read_to_string(&path)?;
         for (index, line) in file.lines().enumerate() {
-            let mut line = line.replace("=>", &format!("=>({})=>", index + 1));
-            line.push('\n');
+            let line = line.replace("=>", &format!("=>({})=>", index + 1));
             code.push_str(&line);
+            code.push('\n');
         }
 
         code.push_str("}),");
     }
+
     code.push(']');
 
-    fs::write("tests/cache/parsing.rs", code).unwrap();
+    fs::write("tests/cache/parse", code)?;
+
+    Ok(())
 }