Fix WASM global vars (#2006)

* fix global wasm vars with one simple trick

* fix ts tests

* changeset

Author: YaroShkvorets

.changeset/tangy-clowns-thank.md

@@ -0,0 +1,5 @@
+---
+'@graphprotocol/graph-ts': patch
+---
+
+fix global variables in wasm

packages/ts/chain/arweave.ts

@@ -1,3 +1,4 @@
+import '../common/eager_offset';
 import { Bytes } from '../common/collections';
 
 // Most types from this namespace are direct mappings or adaptations from:

packages/ts/chain/cosmos.ts

@@ -1,3 +1,4 @@
+import '../common/eager_offset';
 import { Bytes } from '../common/collections';
 
 export namespace cosmos {

packages/ts/chain/ethereum.ts

@@ -1,3 +1,4 @@
+import '../common/eager_offset';
 import { Bytes, Wrapped } from '../common/collections';
 import { Address, BigInt } from '../common/numbers';
 

packages/ts/chain/near.ts

@@ -1,3 +1,4 @@
+import '../common/eager_offset';
 import { Bytes } from '../common/collections';
 import { BigInt } from '../common/numbers';
 

packages/ts/chain/starknet.ts

@@ -1,3 +1,4 @@
+import '../common/eager_offset';
 import { Bytes } from '../common/collections';
 import { BigInt } from '../common/numbers';
 

packages/ts/common/conversion.ts

@@ -1,3 +1,4 @@
+import './eager_offset';
 import { Bytes } from './collections';
 
 /** Host type conversion interface */

packages/ts/common/datasource.ts

@@ -1,3 +1,4 @@
+import './eager_offset';
 import { Entity } from './collections';
 import { Address } from './numbers';
 

packages/ts/common/eager_offset.ts

@@ -0,0 +1,42 @@
+// # What is this file?
+// This file is a "hack" to allow global variables in subgraphs and
+// on this library (`graph-ts`).
+//
+// # Why is it needed?
+// It's necessary because of one of the features of the AssemblyScript
+// compiler we use, the stub runtime.
+//
+// The problem happens because we call the stub runtime allocation
+// (`__alloc`) directly on Rust side (`graph-node`), and that doesn't
+// trigger some AssemblyScript aspects of the code.
+//
+// If you take a look at the stub runtime's code, you'll see that the
+// `__alloc` function uses a variable named `offset` tagged as `lazy`.
+// Like said above, since we call it on Rust side, this variable is not
+// "triggered" to be used, then it's declared below the `__alloc` call
+// in the compiled WASM code.
+//
+// That makes the `graph-node` WASM runtime break because of this out
+// of order variable usage.
+//
+// # How does this fix the issue?
+// The way this workaround works is by calling the `__alloc` function
+// before everything in the AssemblyScript side. This makes the `offset`
+// `lazy` variable be eagerly evaluated when the mappings are compiled
+// (since they always import `graph-ts`).
+//
+// So when we're on Rust side calling `__alloc` it will be fine, because
+// the `offset` is declared before call (order fixed because of this file).
+//
+// The 0 argument to the function call is just because we need no memory
+// to be allocated.
+//
+// # IMPORTANT
+// This should be imported in EVERY file which uses external namespaces (`graph-node` host-exports code),
+// just to make sure no one imports a file directly and gets an error on global variables.
+//
+// # Reference
+// - Runtimes in AS: https://www.assemblyscript.org/garbage-collection.html#runtime-variants
+// - `offset` variable in question: https://github.com/AssemblyScript/assemblyscript/blob/f4091b8f3b6b029d30cd917cf84d97421faadeeb/std/assembly/rt/stub.ts#L9
+// @ts-expect-error We do not want to expose __alloc, hence why we just ignore the error
+__alloc(0);

packages/ts/common/json.ts

@@ -1,3 +1,4 @@
+import './eager_offset';
 import { Bytes, Result } from './collections';
 import { BigInt } from './numbers';
 import { JSONValue } from './value';