From ba0c6a98e6ede3ef3591ac53114abc89ff961092 Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Mon, 5 Aug 2019 13:01:39 -0700
Subject: [PATCH] Fix anyref table export in empty modules

This commit fixes an issue previously introduced around handling the
anyref table, gracefully handling the case where the source module
doesn't actually use the anyref table at all, meaning that the logic
around initializing it can be entirely skipped.
---
 crates/cli-support/src/js/mod.rs     | 22 ----------------------
 crates/cli-support/src/webidl/mod.rs | 19 +++++++++++++++++++
 2 files changed, 19 insertions(+), 22 deletions(-)

diff --git a/crates/cli-support/src/js/mod.rs b/crates/cli-support/src/js/mod.rs
index 863285fc..54649d22 100644
--- a/crates/cli-support/src/js/mod.rs
+++ b/crates/cli-support/src/js/mod.rs
@@ -1152,7 +1152,6 @@ impl<'a> Context<'a> {
         }
         self.expose_uint32_memory();
         if self.config.anyref {
-            self.expose_anyref_table();
             self.global(
                 "
                 function getArrayJsValueFromWasm(ptr, len) {
@@ -1834,30 +1833,11 @@ impl<'a> Context<'a> {
         true
     }
 
-    fn expose_anyref_table(&mut self) {
-        assert!(self.config.anyref);
-        if !self.should_write_global("anyref_table") {
-            return;
-        }
-        let table = self
-            .module
-            .tables
-            .iter()
-            .find(|t| match t.kind {
-                walrus::TableKind::Anyref(_) => true,
-                _ => false,
-            })
-            .expect("failed to find anyref table in module")
-            .id();
-        self.module.exports.add("__wbg_anyref_table", table);
-    }
-
     fn expose_add_to_anyref_table(&mut self) -> Result<(), Error> {
         assert!(self.config.anyref);
         if !self.should_write_global("add_to_anyref_table") {
             return Ok(());
         }
-        self.expose_anyref_table();
         self.require_internal_export("__wbindgen_anyref_table_alloc")?;
         self.global(
             "
@@ -2640,8 +2620,6 @@ impl<'a> Context<'a> {
             }
 
             Intrinsic::InitAnyrefTable => {
-                self.expose_anyref_table();
-
                 // Grow the table to insert our initial values, and then also
                 // set the 0th slot to `undefined` since that's what we've
                 // historically used for our ABI which is that the index of 0
diff --git a/crates/cli-support/src/webidl/mod.rs b/crates/cli-support/src/webidl/mod.rs
index e8119b73..d6500637 100644
--- a/crates/cli-support/src/webidl/mod.rs
+++ b/crates/cli-support/src/webidl/mod.rs
@@ -623,6 +623,24 @@ impl<'a> Context<'a> {
         if !self.anyref_enabled {
             return Ok(());
         }
+
+        // Make sure to export the `anyref` table for the JS bindings since it
+        // will need to be initialized. If it doesn't exist though then the
+        // module must not use it, so we skip it.
+        let table = self
+            .module
+            .tables
+            .iter()
+            .find(|t| match t.kind {
+                walrus::TableKind::Anyref(_) => true,
+                _ => false,
+            });
+        let table = match table {
+            Some(t) => t.id(),
+            None => return Ok(()),
+        };
+        self.module.exports.add("__wbg_anyref_table", table);
+
         let ty = self.module.types.add(&[], &[]);
         let (import, import_id) = self.module.add_import_func(
             PLACEHOLDER_MODULE,
@@ -640,6 +658,7 @@ impl<'a> Context<'a> {
             None => import,
         });
         self.bind_intrinsic(import_id, Intrinsic::InitAnyrefTable)?;
+
         Ok(())
     }