wasi: add returnOnExit option

This commit adds a WASI option allowing the __wasi_proc_exit() function to return an exit code instead of forcefully terminating the process. PR-URL: #32101Fixes: #32093 Reviewed-By: James M Snell <[email protected]> Reviewed-By: Gus Caplan <[email protected]> Reviewed-By: Anna Henningsen <[email protected]> Reviewed-By: Ben Noordhuis <[email protected]> Reviewed-By: Tobias Nießen <[email protected]>

Author: cjihrig

doc/api/wasi.md

@@ -58,6 +58,10 @@ added: v13.3.0
  sandbox directory structure. The string keys of `preopens` are treated as
  directories within the sandbox. The corresponding values in `preopens` are
  the real paths to those directories on the host machine.
+*`returnOnExit`{boolean} By default, WASI applications terminate the Node.js
+ process via the `__wasi_proc_exit()` function. Setting this option to `true`
+ causes `wasi.start()` to return the exit code rather than terminate the
+ process. **Default:**`false`.
 
 ### `wasi.start(instance)`
 <!-- YAML

lib/wasi.js

@@ -15,6 +15,7 @@ const{
 }=require('internal/errors').codes;
 const{ emitExperimentalWarning }=require('internal/util');
 const{WASI: _WASI}=internalBinding('wasi');
+constkExitCode=Symbol('exitCode');
 constkSetMemory=Symbol('setMemory');
 constkStarted=Symbol('started');
 
@@ -26,7 +27,7 @@ class WASI{
 if(options===null||typeofoptions!=='object')
 thrownewERR_INVALID_ARG_TYPE('options','object',options);
 
-const{ env, preopens }=options;
+const{ env, preopens, returnOnExit =false}=options;
 let{ args =[]}=options;
 
 if(ArrayIsArray(args))
@@ -56,16 +57,26 @@ class WASI{
 thrownewERR_INVALID_ARG_TYPE('options.preopens','Object',preopens);
 }
 
+if(typeofreturnOnExit!=='boolean'){
+thrownewERR_INVALID_ARG_TYPE(
+'options.returnOnExit','boolean',returnOnExit);
+}
+
 constwrap=new_WASI(args,envPairs,preopenArray);
 
 for(constpropinwrap){
 wrap[prop]=FunctionPrototypeBind(wrap[prop],wrap);
 }
 
+if(returnOnExit){
+wrap.proc_exit=FunctionPrototypeBind(wasiReturnOnProcExit,this);
+}
+
 this[kSetMemory]=wrap._setMemory;
 deletewrap._setMemory;
 this.wasiImport=wrap;
 this[kStarted]=false;
+this[kExitCode]=0;
 }
 
 start(instance){
@@ -93,12 +104,30 @@ class WASI{
 this[kStarted]=true;
 this[kSetMemory](memory);
 
-if(exports._start)
-exports._start();
-elseif(exports.__wasi_unstable_reactor_start)
-exports.__wasi_unstable_reactor_start();
+try{
+if(exports._start)
+exports._start();
+elseif(exports.__wasi_unstable_reactor_start)
+exports.__wasi_unstable_reactor_start();
+}catch(err){
+if(err!==kExitCode){
+throwerr;
+}
+}
+
+returnthis[kExitCode];
 }
 }
 
 
 module.exports={WASI};
+
+
+functionwasiReturnOnProcExit(rval){
+// If __wasi_proc_exit() does not terminate the process, an assertion is
+// triggered in the wasm runtime. Node can sidestep the assertion and return
+// an exit code by recording the exit code, and throwing a JavaScript
+// exception that WebAssembly cannot catch.
+this[kExitCode]=rval;
+throwkExitCode;
+}

test/wasi/test-return-on-exit.js

@@ -0,0 +1,18 @@
+// Flags: --experimental-wasi-unstable-preview1 --experimental-wasm-bigint
+'use strict';
+constcommon=require('../common');
+constassert=require('assert');
+constfs=require('fs');
+constpath=require('path');
+const{WASI}=require('wasi');
+constwasi=newWASI({returnOnExit: true});
+constimportObject={wasi_snapshot_preview1: wasi.wasiImport};
+constwasmDir=path.join(__dirname,'wasm');
+constmodulePath=path.join(wasmDir,'exitcode.wasm');
+constbuffer=fs.readFileSync(modulePath);
+
+(async()=>{
+const{ instance }=awaitWebAssembly.instantiate(buffer,importObject);
+
+assert.strictEqual(wasi.start(instance),120);
+})().then(common.mustCall());

test/wasi/test-wasi-options-validation.js

@@ -21,6 +21,10 @@ assert.throws(() =>{new WASI({env: 'fhqwhgads'})},
 assert.throws(()=>{newWASI({preopens: 'fhqwhgads'});},
 {code: 'ERR_INVALID_ARG_TYPE',message: /\bpreopens\b/});
 
+// If returnOnExit is not a boolean and not undefined, it should throw.
+assert.throws(()=>{newWASI({returnOnExit: 'fhqwhgads'});},
+{code: 'ERR_INVALID_ARG_TYPE',message: /\breturnOnExit\b/});
+
 // If options is provided, but not an object, the constructor should throw.
 [null,'foo','',0,NaN,Symbol(),true,false,()=>{}].forEach((value)=>{
 assert.throws(()=>{newWASI(value);},