Merge pull request #96 from ScreamingHawk/terminate

Add teardown to cli commands

src/cli.ts

@@ -4,6 +4,7 @@ import {Circomkit} from './core';
 import {existsSync, readFileSync, readdirSync, writeFileSync} from 'fs';
 import {prettyStringify} from './utils';
 import {exec} from 'child_process';
+import {teardown} from './utils/teardown';
 
 const CONFIG_PATH = './circomkit.json';
 
@@ -214,9 +215,9 @@ function cli(args: string[]) {
   });
 
   ///////////////////////////////////////////////////////////////////////////////
-  const config = new Command('config')
-    .description('print configuration')
-    .action(() => circomkit.log.info(circomkit.config));
+  const config = new Command('config').description('print configuration').action(() => {
+    circomkit.log.info(circomkit.config);
+  });
 
   ///////////////////////////////////////////////////////////////////////////////
   new Command()
@@ -241,6 +242,8 @@ function cli(args: string[]) {
     .addCommand(witness)
     .addCommand(verify)
     .addCommand(calldata)
+    // teardown to terminate SnarkJS, otherwise hangs the program
+    .hook('postAction', async () => await teardown())
     .parse(args);
 
   // TODO: test graceful exits

src/utils/teardown.ts

@@ -0,0 +1,15 @@
+declare global {
+  // eslint-disable-next-line no-var
+  var curve_bn128: {terminate: () => Promise<void>} | undefined;
+}
+
+/**
+ * Teardown function to be run for graceful exits.
+ *
+ * SnarkJS may attach curve_bn128 to global, but does not terminate it.
+ * We have to do it manually (see https://github.com/iden3/snarkjs/issues/152)
+ * For this, we use the [`terminate`](https://github.com/iden3/ffjavascript/blob/master/src/bn128.js#L48) function.
+ */
+export async function teardown() {
+  if (globalThis.curve_bn128) await globalThis.curve_bn128.terminate();
+}