feat: add dependency

javascript-engine/external/boa/fuzz/fuzz_targets/parser-idempotency.rs

@@ -0,0 +1,74 @@
+#![no_main]
+
+mod common;
+
+use crate::common::FuzzData;
+use boa_interner::ToInternedString;
+use boa_parser::Parser;
+use libfuzzer_sys::fuzz_target;
+use libfuzzer_sys::Corpus;
+use std::error::Error;
+use std::io::Cursor;
+
+/// Fuzzer test harness. This function accepts the arbitrary AST and performs the fuzzing operation.
+///
+/// See [README.md](../README.md) for details on the design of this fuzzer.
+fn do_fuzz(mut data: FuzzData) -> Result<(), Box<dyn Error>> {
+    let original = data.ast.to_interned_string(&data.interner);
+
+    let mut parser = Parser::new(Cursor::new(&original));
+
+    let before = data.interner.len();
+    // For a variety of reasons, we may not actually produce valid code here (e.g., nameless function).
+    // Fail fast and only make the next checks if we were valid.
+    if let Ok(first) = parser.parse_all(&mut data.interner) {
+        let after_first = data.interner.len();
+        let first_interned = first.to_interned_string(&data.interner);
+
+        assert_eq!(
+            before,
+            after_first,
+            "The number of interned symbols changed; a new string was read.\nBefore:\n{}\nAfter:\n{}\nBefore (AST):\n{:#?}\nAfter (AST):\n{:#?}",
+            original,
+            first_interned,
+            data.ast,
+            first
+        );
+        let mut parser = Parser::new(Cursor::new(&first_interned));
+
+        // Now, we most assuredly should produce valid code. It has already gone through a first pass.
+        let second = parser
+            .parse_all(&mut data.interner)
+            .expect("Could not parse the first-pass interned copy.");
+        let second_interned = second.to_interned_string(&data.interner);
+        let after_second = data.interner.len();
+        assert_eq!(
+            after_first,
+            after_second,
+            "The number of interned symbols changed; a new string was read.\nBefore:\n{}\nAfter:\n{}\nBefore (AST):\n{:#?}\nAfter (AST):\n{:#?}",
+            first_interned,
+            second_interned,
+            first,
+            second
+        );
+        assert_eq!(
+            first,
+            second,
+            "Expected the same AST after two intern passes, but found dissimilar.\nOriginal:\n{}\nFirst:\n{}\nSecond:\n{}",
+            original,
+            first_interned,
+            second_interned,
+        );
+    }
+    Ok(())
+}
+
+// Fuzz harness wrapper to expose it to libfuzzer (and thus cargo-fuzz)
+// See: https://rust-fuzz.github.io/book/cargo-fuzz.html
+fuzz_target!(|data: FuzzData| -> Corpus {
+    if do_fuzz(data).is_ok() {
+        Corpus::Keep
+    } else {
+        Corpus::Reject
+    }
+});