[PATCH v5 7/7] cache-tree: verify valid cache-tree in the test suite

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

This makes sure that cache-tree is consistent with the index. The main
purpose is to catch potential problems by saving the index in
unpack_trees() but the line in write_index() would also help spot
missing invalidation in other code.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 cache-tree.c   | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++
 cache-tree.h   |  1 +
 read-cache.c   |  3 ++
 t/test-lib.sh  |  6 ++++
 unpack-trees.c |  2 ++
 5 files changed, 90 insertions(+)

diff --git a/cache-tree.c b/cache-tree.c
index caafbff2ff..c3c206427c 100644
--- a/cache-tree.c
+++ b/cache-tree.c
@@ -4,6 +4,7 @@
 #include "tree-walk.h"
 #include "cache-tree.h"
 #include "object-store.h"
+#include "replace-object.h"
 
 #ifndef DEBUG
 #define DEBUG 0
@@ -732,3 +733,80 @@ int update_main_cache_tree(int flags)
 		the_index.cache_tree = cache_tree();
 	return cache_tree_update(&the_index, flags);
 }
+
+static void verify_one(struct index_state *istate,
+		       struct cache_tree *it,
+		       struct strbuf *path)
+{
+	int i, pos, len = path->len;
+	struct strbuf tree_buf = STRBUF_INIT;
+	struct object_id new_oid;
+
+	for (i = 0; i < it->subtree_nr; i++) {
+		strbuf_addf(path, "%s/", it->down[i]->name);
+		verify_one(istate, it->down[i]->cache_tree, path);
+		strbuf_setlen(path, len);
+	}
+
+	if (it->entry_count < 0 ||
+	    /* no verification on tests (t7003) that replace trees */
+	    lookup_replace_object(the_repository, &it->oid) != &it->oid)
+		return;
+
+	if (path->len) {
+		pos = index_name_pos(istate, path->buf, path->len);
+		pos = -pos - 1;
+	} else {
+		pos = 0;
+	}
+
+	i = 0;
+	while (i < it->entry_count) {
+		struct cache_entry *ce = istate->cache[pos + i];
+		const char *slash;
+		struct cache_tree_sub *sub = NULL;
+		const struct object_id *oid;
+		const char *name;
+		unsigned mode;
+		int entlen;
+
+		if (ce->ce_flags & (CE_STAGEMASK | CE_INTENT_TO_ADD | CE_REMOVE))
+			BUG("%s with flags 0x%x should not be in cache-tree",
+			    ce->name, ce->ce_flags);
+		name = ce->name + path->len;
+		slash = strchr(name, '/');
+		if (slash) {
+			entlen = slash - name;
+			sub = find_subtree(it, ce->name + path->len, entlen, 0);
+			if (!sub || sub->cache_tree->entry_count < 0)
+				BUG("bad subtree '%.*s'", entlen, name);
+			oid = &sub->cache_tree->oid;
+			mode = S_IFDIR;
+			i += sub->cache_tree->entry_count;
+		} else {
+			oid = &ce->oid;
+			mode = ce->ce_mode;
+			entlen = ce_namelen(ce) - path->len;
+			i++;
+		}
+		strbuf_addf(&tree_buf, "%o %.*s%c", mode, entlen, name, '\0');
+		strbuf_add(&tree_buf, oid->hash, the_hash_algo->rawsz);
+	}
+	hash_object_file(tree_buf.buf, tree_buf.len, tree_type, &new_oid);
+	if (oidcmp(&new_oid, &it->oid))
+		BUG("cache-tree for path %.*s does not match. "
+		    "Expected %s got %s", len, path->buf,
+		    oid_to_hex(&new_oid), oid_to_hex(&it->oid));
+	strbuf_setlen(path, len);
+	strbuf_release(&tree_buf);
+}
+
+void cache_tree_verify(struct index_state *istate)
+{
+	struct strbuf path = STRBUF_INIT;
+
+	if (!istate->cache_tree)
+		return;
+	verify_one(istate, istate->cache_tree, &path);
+	strbuf_release(&path);
+}
diff --git a/cache-tree.h b/cache-tree.h
index 9799e894f7..c1fde531f9 100644
--- a/cache-tree.h
+++ b/cache-tree.h
@@ -32,6 +32,7 @@ struct cache_tree *cache_tree_read(const char *buffer, unsigned long size);
 
 int cache_tree_fully_valid(struct cache_tree *);
 int cache_tree_update(struct index_state *, int);
+void cache_tree_verify(struct index_state *);
 
 int update_main_cache_tree(int);
 
diff --git a/read-cache.c b/read-cache.c
index 5ce40f39b3..41f313bc9e 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -2744,6 +2744,9 @@ int write_locked_index(struct index_state *istate, struct lock_file *lock,
 	int new_shared_index, ret;
 	struct split_index *si = istate->split_index;
 
+	if (git_env_bool("GIT_TEST_CHECK_CACHE_TREE", 0))
+		cache_tree_verify(istate);
+
 	if ((flags & SKIP_IF_UNCHANGED) && !istate->cache_changed) {
 		if (flags & COMMIT_LOCK)
 			rollback_lock_file(lock);
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 78f7097746..5b50f6e2e6 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -1083,6 +1083,12 @@ else
 	test_set_prereq C_LOCALE_OUTPUT
 fi
 
+if test -z "$GIT_TEST_CHECK_CACHE_TREE"
+then
+	GIT_TEST_CHECK_CACHE_TREE=true
+	export GIT_TEST_CHECK_CACHE_TREE
+fi
+
 test_lazy_prereq PIPE '
 	# test whether the filesystem supports FIFOs
 	test_have_prereq !MINGW,!CYGWIN &&
diff --git a/unpack-trees.c b/unpack-trees.c
index bc43922922..3394540842 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -1578,6 +1578,8 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 	if (o->dst_index) {
 		move_index_extensions(&o->result, o->src_index);
 		if (!ret) {
+			if (git_env_bool("GIT_TEST_CHECK_CACHE_TREE", 0))
+				cache_tree_verify(&o->result);
 			if (!o->result.cache_tree)
 				o->result.cache_tree = cache_tree();
 			if (!cache_tree_fully_valid(o->result.cache_tree))
-- 
2.18.0.1004.g6639190530