From 273645805a18afee14574c945fa916d2b1b12692 Mon Sep 17 00:00:00 2001
From: milner <m@cpl0.zip>
Date: Wed, 17 Aug 2022 19:24:25 +0000
Subject: [PATCH] fix(watch): drop the digest memo between rounds

---
 bin/meowc.ml | 1 +
 lib/cache.ml | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/bin/meowc.ml b/bin/meowc.ml
index 16c625d..5d2a6e2 100644
--- a/bin/meowc.ml
+++ b/bin/meowc.ml
@@ -535,6 +535,7 @@ let cmd_compdb () =
 
 let cmd_watch names =
   let round () =
+    Cache.reset ();
     let p = configure () in
     with_config_header p;
     let t0 = Unix.gettimeofday () in
diff --git a/lib/cache.ml b/lib/cache.ml
index db70a0a..5299a97 100644
--- a/lib/cache.ml
+++ b/lib/cache.ml
@@ -36,6 +36,10 @@ let digest_file p =
 
 let forget p = Hashtbl.remove digests p
 
+(* The memo saves re-hashing a header that half the project includes, so it is
+   only ever valid for one build. A watch loop runs many in one process. *)
+let reset () = Hashtbl.reset digests
+
 let key ~cmd ~inputs =
   let b = Buffer.create 256 in
   Buffer.add_string b cmd;