[js] Attach exceptions on contexts instead of putting them on a stack

On fibers we could have continuation local stacks on async/await continuations
it's harder.

This was causing problems when zipping sequences and resuming all the TAKE control
exceptions got intertwined.
 # Please enter the commit message for your changes. Lines starting

Author: pmurias

src/vm/js/Operations.nqp

@@ -881,7 +881,7 @@ class QAST::OperationsJS {
     });
 
 
-    add_simple_op('exception', $T_OBJ, []);
+    add_simple_op('exception', $T_OBJ, [], sub () {"$*CTX.\$\$exception()"});
     add_simple_op('rethrow', $T_VOID, [$T_OBJ], sub ($exception) {"/*await*/ $*CTX.rethrow($exception)"}, :side_effects);
     add_simple_op('resume', $T_VOID, [$T_OBJ], sub ($exception) {"/*await*/ $*CTX.resume($exception)"}, :side_effects);
     add_simple_op('throw', $T_VOID, [$T_OBJ], :side_effects, sub ($exception) {"/*await*/ {$*CTX}.throw($exception)"});
@@ -1511,14 +1511,18 @@ class QAST::OperationsJS {
             else {
                 my $unwind_marker := $*BLOCK.add_tmp;
 
-                my $handle_result := $comp.as_js(:want($T_OBJ), $node[2]);
+                my $handle_result;
+                {
+                    my $*CTX := '$$ctx';
+                    $handle_result := $comp.as_js(:want($T_OBJ), $node[2]);
+                }
                 my str $result := $*BLOCK.add_tmp;
 
 
                 Chunk.new($T_OBJ, $result, [
                     "$unwind_marker = \{\};\n",
                     "$*CTX.\$\$unwind = $unwind_marker;\n",
-                    "$*CTX.\$\${$type} = /*async*/ function() \{\n",
+                    "$*CTX.\$\${$type} = /*async*/ function(\$\$ctx) \{\n",
                         $handle_result,
                         "$result = {$handle_result.expr};\n",
                     "\};\n",
@@ -1564,7 +1568,7 @@ class QAST::OperationsJS {
 
     add_simple_op('throwextype', $T_VOID, [$T_INT], :side_effects, :ctx, :await);
 
-    add_simple_op('lastexpayload', $T_OBJ, [], :!inlinable);
+    add_simple_op('lastexpayload', $T_OBJ, [], sub () {"$*CTX.\$\$lastexpayload()"}, :!inlinable);
 
 
     add_op('control', sub ($comp, $node, :$want) {

src/vm/js/nqp-runtime/core.js

@@ -31,8 +31,6 @@ const null_s = require('./null_s.js');
 
 const BOOT = require('./BOOT.js');
 
-const exceptionsStack = require('./exceptions-stack.js');
-
 const sixmodel = require('./sixmodel.js');
 
 const Capture = require('./capture.js');
@@ -2006,16 +2004,6 @@ op.split = function(currentHLL, separator, string) {
     : []).map(str => strToObj(currentHLL, str)));
 };
 
-op.exception = function() {
-  const stack = exceptionsStack();
-  return stack[stack.length - 1];
-};
-
-op.lastexpayload = function() {
-  const stack = exceptionsStack();
-  return stack[stack.length - 1].$$payload;
-};
-
 op.setextype = function(exception, category) {
   exception.$$category = category;
   return exception;

src/vm/js/nqp-runtime/ctx.js

@@ -3,7 +3,6 @@ const NQPExceptionWithCtx = require('./nqp-exception-with-ctx.js');
 const NQPException = require('./nqp-exception.js');
 const NQPObject = require('./nqp-object.js');
 const Null = require('./null.js');
-const exceptionsStack = require('./exceptions-stack.js');
 
 const BOOT = require('./BOOT.js');
 
@@ -117,9 +116,10 @@ class Ctx extends NQPObject {
         exception.caught = ctx;
         ctx.exception = exception;
 
-        exceptionsStack().push(exception);
         try {
           const wrapped = new Ctx(this, this, null);
+          wrapped.$$currentException = exception;
+
           if (ctx[handler]) {
             ctx.$$unwind.ret = /*await*/ ctx[handler](wrapped);
           } else {
@@ -131,8 +131,6 @@ class Ctx extends NQPObject {
           } else {
             throw e;
           }
-        } finally {
-          exceptionsStack().pop();
         }
 
         throw ctx.$$unwind;
@@ -173,20 +171,18 @@ class Ctx extends NQPObject {
         exception.caught = ctx;
         ctx.exception = exception;
 
-        exceptionsStack().push(exception);
+
         try {
           const wrapped = new Ctx(this, this, null);
+          wrapped.$$currentException = exception;
           ctx.$$unwind.ret = /*await*/ ctx.$$CATCH(wrapped);
         } catch (e) {
           if (e instanceof ResumeException && e.exception === exception) {
             return;
           } else {
             throw e;
           }
-        } finally {
-          exceptionsStack().pop();
         }
-
         throw ctx.$$unwind;
       }
       ctx = ctx.$$caller;
@@ -210,14 +206,10 @@ class Ctx extends NQPObject {
   }
 
   /*async*/ catchException(exception) {
-    this.exception = exception;
-    exceptionsStack().push(exception);
-    try {
-      // we don't have access to the most correct ctx in case of this sort of exception
-      return /*await*/ this.$$CATCH(this);
-    } finally {
-      exceptionsStack().pop();
-    }
+    // we don't have access to the most correct ctx in case of this sort of exception
+    const wrapped = new Ctx(this, this, null);
+    wrapped.$$currentException = exception;
+    return /*await*/ this.$$CATCH(wrapped);
   }
 
   rethrow(exception) {
@@ -277,9 +269,9 @@ class Ctx extends NQPObject {
         exception.caught = ctx;
         ctx.exception = exception;
 
-        exceptionsStack().push(exception);
         try {
           const wrapped = new Ctx(this, this, null);
+          wrapped.$$currentException = exception;
           if (ctx[handler]) {
             ctx.$$unwind.ret = /*await*/ ctx[handler](wrapped);
           } else {
@@ -291,8 +283,6 @@ class Ctx extends NQPObject {
           } else {
             throw e;
           }
-        } finally {
-          exceptionsStack().pop();
         }
 
         let check = lookFrom;
@@ -378,6 +368,22 @@ class Ctx extends NQPObject {
     return this.$$outer.lookup(name);
   }
 
+  $$exception() {
+    let ctx = this;
+    while (ctx) {
+      if (ctx.$$currentException) {
+        return ctx.$$currentException;
+      }
+      ctx = ctx.$$caller;
+    }
+
+    console.log('exception not found');
+  }
+
+  $$lastexpayload() {
+    return this.$$exception().$$payload;
+  }
+
   $$getHLL() {
     let ctx = this;
     while (ctx) {