Fix singleton printing bug

Author: lpil

src/gleam_stdlib.mjs

@@ -701,14 +701,22 @@ class Inspector {
       return "//js(circular reference)";
     }
 
-    if (Array.isArray(v))
-      return `#(${v.map((v) => this.inspect(v)).join(", ")})`;
-    if (v instanceof List) return this.#list(v);
-    if (v instanceof CustomType) return this.#customType(v);
-    if (v instanceof Dict) return this.#dict(v);
-    if (v instanceof Set)
+    let printed;
+    if (Array.isArray(v)) {
+      printed = `#(${v.map((v) => this.inspect(v)).join(", ")})`;
+    } else if (v instanceof List) {
+      printed = this.#list(v);
+    } else if (v instanceof CustomType) {
+      printed = this.#customType(v);
+    } else if (v instanceof Dict) {
+      printed = this.#dict(v);
+    } else if (v instanceof Set) {
       return `//js(Set(${[...v].map((v) => this.inspect(v)).join(", ")}))`;
-    return this.#object(v);
+    } else {
+      printed = this.#object(v);
+    }
+    this.#references.delete(v);
+    return printed;
   }
 
   #object(v) {

test/gleam/string_test.gleam

@@ -1252,6 +1252,16 @@ pub fn inspect_circular_reference_test() {
     == "#(1, 2, 3, //js(circular reference))"
 }
 
+@target(javascript)
+@external(javascript, "../gleam_stdlib_test_ffi.mjs", "singleton_object")
+fn singleton_object() -> Dynamic
+
+@target(javascript)
+pub fn inspect_singleton_test() {
+  assert string.inspect(#(singleton_object(), singleton_object()))
+    == "#(//js({ \"a\": 1 }), //js({ \"a\": 1 }))"
+}
+
 @target(javascript)
 @external(javascript, "../gleam_stdlib_test_ffi.mjs", "js_error")
 fn js_error() -> Dynamic

test/gleam_stdlib_test_ffi.mjs

@@ -27,6 +27,12 @@ export function map(items) {
   return object;
 }
 
+const singleton = { a: 1 };
+
+export function singleton_object() {
+  return singleton;
+}
+
 export function circular_reference() {
   const x = [1, 2, 3];
   x.push(x);