From 1749e71f327d94805fdbb50d0cbbd692f696997d Mon Sep 17 00:00:00 2001
From: Dominic Monroe <dmc@juxt.pro>
Date: Sun, 16 Feb 2020 12:13:41 +0000
Subject: [PATCH] Fix metadata preservation

Close #86
---
 src/aero/alpha/core.cljc | 12 ++++++++----
 src/aero/core.cljc       |  2 +-
 src/aero/impl/walk.cljc  | 22 ++++++++++++++++++++++
 test/aero/core_test.cljc | 20 +++++++++++++++++++-
 4 files changed, 50 insertions(+), 6 deletions(-)
 create mode 100644 src/aero/impl/walk.cljc

diff --git a/src/aero/alpha/core.cljc b/src/aero/alpha/core.cljc
index 1067c3b..b0022d3 100644
--- a/src/aero/alpha/core.cljc
+++ b/src/aero/alpha/core.cljc
@@ -22,22 +22,26 @@
     (and (map? x) (not (record? x)))
     (with-meta
       (into [] x)
-      {`reassemble (fn [_ queue] (into {} queue))})
+      {`reassemble (fn [_ queue] (into (empty x) queue))})
 
     (set? x)
     (with-meta (map-indexed (fn [idx v] [idx v]) x)
                {`reassemble (fn [_ queue]
-                              (set (map second queue)))})
+                              (into (empty x)
+                                    (map second queue)))})
 
     (vector? x)
     (with-meta (map-indexed (fn [idx v] [idx v]) x)
                {`reassemble (fn [_ queue]
-                              (mapv second (sort-by first queue)))})
+                              (into (empty x)
+                                    (mapv second (sort-by first queue))))})
 
     (seq? x)
     (with-meta (map-indexed (fn [idx v] [idx v]) x)
                {`reassemble (fn [_ queue]
-                              (apply list (map second (sort-by first queue))))})
+                              (with-meta
+                                (apply list (map second (sort-by first queue)))
+                                (meta x)))})
     ;; Scalar value
     :else
     nil))
diff --git a/src/aero/core.cljc b/src/aero/core.cljc
index 696c31d..b70b436 100644
--- a/src/aero/core.cljc
+++ b/src/aero/core.cljc
@@ -5,7 +5,7 @@
     [aero.alpha.core :refer
      [expand expand-scalar-repeatedly expand-case eval-tagged-literal
       reassemble kv-seq]]
-    [clojure.walk :refer [walk postwalk]]
+    [aero.impl.walk :refer [postwalk]]
     #?@(:clj [[clojure.edn :as edn]
               [aero.impl.macro :as macro]]
         :cljs [[cljs.tools.reader.edn :as edn]
diff --git a/src/aero/impl/walk.cljc b/src/aero/impl/walk.cljc
new file mode 100644
index 0000000..3239ed2
--- /dev/null
+++ b/src/aero/impl/walk.cljc
@@ -0,0 +1,22 @@
+(ns aero.impl.walk)
+
+(defn- walk
+  [inner outer form]
+  (let [x (cond
+            (list? form) (outer (apply list (map inner form)))
+            #?@(:cljs [(map-entry? form) (outer (MapEntry. (inner (key form)) (inner (val form)) nil))]
+                :clj [(instance? clojure.lang.IMapEntry form) (outer (vec (map inner form)))])
+            (seq? form) (outer (doall (map inner form)))
+            #?(:cljs (record? form)
+               :clj (instance? clojure.lang.IRecord form))
+            (outer (reduce (fn [r x] (conj r (inner x))) form form))
+            (coll? form) (outer (into (empty form) (map inner form)))
+            :else (outer form))]
+    (if #?(:cljs (implements? IWithMeta x)
+           :clj (instance? clojure.lang.IObj x))
+      (with-meta x (merge (meta form) (meta x)))
+      x)))
+
+(defn postwalk
+  [f form]
+  (walk (partial postwalk f) f form))
diff --git a/test/aero/core_test.cljc b/test/aero/core_test.cljc
index b896abe..3510c22 100644
--- a/test/aero/core_test.cljc
+++ b/test/aero/core_test.cljc
@@ -8,7 +8,7 @@
   #?(:clj (:import [aero.core Deferred]))
   #?(:cljs (:require [aero.core :refer [read-config reader Deferred] :refer-macros [deferred]]
                      [cljs.tools.reader :as edn]
-                     [cljs.test :refer [deftest is testing]]
+                     [cljs.test :refer [deftest is testing are]]
                      [goog.object :as gobj]
                      [goog.string :as gstring]
                      goog.string.format
@@ -231,3 +231,21 @@
         config (#?(:cljs source-logging-push-back-reader
                    :clj java.io.StringReader.) config-str)]
     (is (= "bar" (:y (read-config config))))))
+
+(deftest meta-preservation-test
+  (are [ds] (= ds
+               (::foo
+                 (meta
+                   (read-config
+                     (#?(:cljs source-logging-push-back-reader
+                         :clj java.io.StringReader.)
+                               (binding [*print-meta* true]
+                                 (pr-str (with-meta ds {::foo ds}))))))))
+    []
+    {}
+    #{}
+    ()
+    [1]
+    {:a :b}
+    #{:a :b}
+    '(1)))