From 13a5c313121e967db569d61568cf0fd25fe60eb3 Mon Sep 17 00:00:00 2001
From: Nikita Prokopov <niki@tonsky.me>
Date: Mon, 22 Jul 2024 16:36:18 +0200
Subject: [PATCH] Fixed `find-datom` on empty DB (closes #477)

---
 CHANGELOG.md                    | 4 ++++
 src/datascript/db.cljc          | 2 +-
 test/datascript/test/index.cljc | 6 +++++-
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 20428e90..c6d9842e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+# WIP
+
+- Fixed `find-datom` on empty DB #477 thx @RCmerci
+
 # 1.7.2 - Jul 4, 2024
 
 - Regression: transacting many ref value as a set of inline maps #476 
diff --git a/src/datascript/db.cljc b/src/datascript/db.cljc
index fc5e2cae..3ee5941a 100644
--- a/src/datascript/db.cljc
+++ b/src/datascript/db.cljc
@@ -1149,7 +1149,7 @@
         cmp     #?(:clj (.comparator ^clojure.lang.Sorted set) :cljs (.-comparator set))
         from    (components->pattern db index c0 c1 c2 c3 e0 tx0)
         to      (components->pattern db index c0 c1 c2 c3 emax txmax)
-        datom   (when-let [set* (seq set)] (first (set/seek set* from)))]
+        datom   (some-> set seq (set/seek from) first)]
     (when (and (some? datom) (<= 0 (cmp to datom)))
       datom)))
 
diff --git a/test/datascript/test/index.cljc b/test/datascript/test/index.cljc
index 2845e6fb..094c30f4 100644
--- a/test/datascript/test/index.cljc
+++ b/test/datascript/test/index.cljc
@@ -102,7 +102,11 @@
     (is (= [2 :name "Ivan"] (dvec (d/find-datom db :eavt 2 :name))))
     
     (is (= nil (dvec (d/find-datom db :eavt 1 :name "Ivan"))))
-    (is (= nil (dvec (d/find-datom db :eavt 4))))))
+    (is (= nil (dvec (d/find-datom db :eavt 4))))
+    
+    ;; issue-477
+    (is (= nil (d/find-datom (d/empty-db) :eavt)))
+    (is (= nil (d/find-datom (d/empty-db {:age {:db/index true}}) :eavt)))))
 
 (deftest test-seek-datoms
   (let [dvec #(vector (:e %) (:a %) (:v %))