Restore fuzz test harness (#1246)

fuzz/Cargo.toml

@@ -1,5 +1,5 @@
 [package]
-name    = "just-fuzz"
+name = "just-fuzz"
 version = "0.0.0"
 authors = ["Automatically generated"]
 publish = false
@@ -8,8 +8,21 @@ edition = "2018"
 [package.metadata]
 cargo-fuzz = true
 
+[dependencies]
+libfuzzer-sys = "0.4"
+
 [dependencies.just]
 path = ".."
 
-[dependencies.libfuzzer-sys]
-git = "https://github.com/rust-fuzz/libfuzzer-sys.git"
+# Prevent this from interfering with workspaces
+[workspace]
+members = ["."]
+
+[[bin]]
+name = "compile"
+path = "fuzz_targets/compile.rs"
+test = false
+doc = false
+
+[profile.release]
+debug = true

fuzz/fuzz_targets/compile.rs

@@ -0,0 +1,6 @@
+#![no_main]
+use libfuzzer_sys::fuzz_target;
+
+fuzz_target!(|src: &str| {
+  let _ = just::fuzzing::compile(src);
+});

src/fuzzing.rs

@@ -1,9 +1,5 @@
 use super::*;
 
-pub(crate) fn compile(text: &str) {
-  if let Err(error) = Parser::parse(text) {
-    if let CompileErrorKind::Internal { .. } = error.kind {
-      panic!("{}", error)
-    }
-  }
+pub fn compile(text: &str) {
+  let _ = compiler::Compiler::compile(text);
 }

src/lib.rs

@@ -104,7 +104,7 @@ pub mod tree;
 pub mod node;
 
 #[cfg(fuzzing)]
-pub(crate) mod fuzzing;
+pub mod fuzzing;
 
 // Used by Janus, https://github.com/casey/janus, a tool
 // that analyses all public justfiles on GitHub to avoid