From 5bf8d77bc14fe0a8116362117467f000568604ef Mon Sep 17 00:00:00 2001
From: Ben Visness <bvisness@mozilla.com>
Date: Thu, 27 Aug 2026 10:41:57 -0500
Subject: [PATCH 1/2] Allow empty import groups in the spec interpreter (#22)

Ensures that both forms of compact import group accept zero items in
the reference interpreter, and that externtypes still behave the same
way they usually would even in an empty compact-2 group.
---
 interpreter/text/parser.mly                   | 11 ++++--
 .../imports-compact.wast                      | 34 +++++++++++++++++++
 2 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/interpreter/text/parser.mly b/interpreter/text/parser.mly
index 6ea942796..6d698ef11 100644
--- a/interpreter/text/parser.mly
+++ b/interpreter/text/parser.mly
@@ -133,6 +133,7 @@ let empty_context () =
     datas = empty (); elems = empty (); locals = empty (); labels = empty ();
     deferred_locals = ref []
   }
+let empty_context_with_types_from (c : context) = {(empty_context ()) with types = c.types}
 
 let enter_block (c : context) loc = {c with labels = scoped "label" 1l c.labels (at loc)}
 let enter_let (c : context) loc = {c with locals = empty (); deferred_locals = ref []}
@@ -1258,9 +1259,8 @@ compact_item1 :
       fun () -> ($3, df ()) }
 
 compact_item1_list :
-  | compact_item1
-    { fun c -> let f = $1 c in
-      fun () -> [f ()] }
+  | /* empty */
+    { fun _c -> fun () -> [] }
   | compact_item1 compact_item1_list
     { fun c -> let f = $1 c in let fs = $2 c in
       fun () -> f () :: fs () }
@@ -1283,8 +1283,13 @@ import :
   | LPAR IMPORT name compact_item2_list RPAR
     { fun c ->
       let (item_names, xt_fn) = $4 in
+      (* Run the externtype function once, even if there are zero items, to
+       * ensure it has no identifiers and to ensure that any implicit function
+       * types still get defined. *)
+      let df0 = xt_fn (empty_context_with_types_from c) false in
       let dfs = List.map (fun _ -> xt_fn c false) item_names in
       fun () ->
+        ignore (df0 ());
         List.map2 (fun item_name df -> Import ($3, item_name, df ()) @@ $sloc)
           item_names dfs }
 
diff --git a/test/core/compact-import-section/imports-compact.wast b/test/core/compact-import-section/imports-compact.wast
index 577967020..188c2824c 100644
--- a/test/core/compact-import-section/imports-compact.wast
+++ b/test/core/compact-import-section/imports-compact.wast
@@ -97,6 +97,32 @@
 )
 
 
+;; Zero-length groups
+
+(module (import "not-test")) ;; encoding 1
+(module (import "not-test" (func))) ;; encoding 2
+
+(module
+  (import "test")
+  (import "test" (func (result i32)))                       ;; no func
+  (import "test" (item "func->11i" (func (result i32))))    ;; func 0
+  (import "test" (global i32))                              ;; no global
+  (import "test" (item "global->20") (global i32))          ;; global 0
+
+  (func (export "check") (result i32)
+    call 0
+    global.get 0
+    i32.add
+  )
+)
+(assert_return (invoke "check") (i32.const 31))
+
+(module
+  (import "not-test" (func (param i32)))  ;; still implicitly defines a func type
+  (func (type 0))
+)
+
+
 ;; Identifiers
 
 (module
@@ -118,10 +144,18 @@
 
 (assert_return (invoke "sum") (i32.const 32))
 
+(assert_malformed
+  (module quote "(import \"test\" (func $foo))")
+  "identifier not allowed"
+)
 (assert_malformed
   (module quote "(import \"test\" (item \"foo\") (func $foo))")
   "identifier not allowed"
 )
+(assert_malformed
+  (module quote "(import \"test\" (item \"foo\") (item \"bar\") (func $foo))")
+  "identifier not allowed"
+)
 
 
 ;; All externtype kinds in a single encoding-1 group

From 3428dc236f07647c711adc1112162f34e12bfe7e Mon Sep 17 00:00:00 2001
From: Ben Visness <bvisness@mozilla.com>
Date: Thu, 27 Aug 2026 12:10:46 -0500
Subject: [PATCH 2/2] Update tests

---
 spectec/doc/example/output/NanoWasm.pdf | Bin 244360 -> 244360 bytes
 1 file changed, 0 insertions(+), 0 deletions(-)

diff --git a/spectec/doc/example/output/NanoWasm.pdf b/spectec/doc/example/output/NanoWasm.pdf
index ffc8d13cfe155a692e2e5a08dc214cb05291c652..af4d0a661b2b56005521fd7725a37576df48d771 100644
GIT binary patch
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