wasm: avoid using a crashed Process

Author: strager

wasm/quick-lint-js.js

@@ -389,22 +389,26 @@ class ProcessFactory {
   }
 }
 
+let nextProcessIDForDebugging = 1;
+
 // A WebAssembly instance.
 //
 // If a Process crashes, every DocumentForVSCode or DocumentForWebDemo
 // associated with its creating Process is tainted and should not be used
 // anymore.
 class Process {
   constructor(wasmInstance) {
+    this._idForDebugging = nextProcessIDForDebugging++;
     this._wasmInstance = wasmInstance;
 
+    let process = this;
     function wrap(name) {
       if (!Object.prototype.hasOwnProperty.call(wasmInstance.exports, name)) {
         throw new TypeError(`WASM does not export function: ${name}`);
       }
       let func = wasmInstance.exports[name];
       return (...args) => {
-        exports.maybeInjectFault(name);
+        exports.maybeInjectFault(process, name);
         try {
           return func(...args);
         } catch (e) {
@@ -427,6 +431,10 @@ class Process {
     this._webDemoSetText = wrap("qljs_web_demo_set_text");
   }
 
+  toString() {
+    return `Process(id=${this._idForDebugging})`;
+  }
+
   async createDocumentForVSCodeAsync() {
     return new DocumentForVSCode(this);
   }
@@ -454,8 +462,14 @@ class DocumentForVSCode {
         utf8ReplacementText.pointer,
         utf8ReplacementText.byteSize
       );
-    } finally {
       utf8ReplacementText.dispose();
+    } catch (e) {
+      if (e instanceof ProcessCrashed) {
+        // Don't touch the Process.
+      } else {
+        utf8ReplacementText.dispose();
+      }
+      throw e;
     }
   }
 
@@ -656,7 +670,7 @@ function assertEqual(actual, expected) {
 //
 // Replace this function with a function which throws an exception to simulate
 // errors such as segfaults and OOMs.
-exports.maybeInjectFault = () => {};
+exports.maybeInjectFault = (_process, _functionName) => {};
 
 // quick-lint-js finds bugs in JavaScript programs.
 // Copyright (C) 2020  Matthew "strager" Glazar

wasm/test-document.js

@@ -201,7 +201,12 @@ describe("DocumentLinter", () => {
 
     let coinFlips;
     let rng = new ExhaustiveRNG();
-    qljs.maybeInjectFault = (functionName) => {
+    let crashedProcesses = new Set();
+    qljs.maybeInjectFault = (process, functionName) => {
+      assert.ok(
+        !crashedProcesses.has(process),
+        "Should not use previously-crashed process"
+      );
       // TODO(strager): Figure out why qljs_vscode_create_document failures
       // cause this test to fail.
       // TODO(strager): Fix problems when qljs_vscode_destroy_document fails.
@@ -212,6 +217,7 @@ describe("DocumentLinter", () => {
         let shouldCrash = rng.nextCoinFlip();
         coinFlips.push(shouldCrash);
         if (shouldCrash) {
+          crashedProcesses.add(process);
           throw new ProcessCrashed("(injected fault)");
         }
       }
@@ -268,6 +274,8 @@ describe("DocumentLinter", () => {
 
       console.log(`coinFlips: ${coinFlips}`);
       rng.lap();
+
+      crashedProcesses.clear(); // Avoid out-of-memory errors.
     }
 
     async function didLintingCrashAsync(callback) {
@@ -287,12 +295,18 @@ describe("DocumentLinter", () => {
   it("concurrent edits are applied in order of calls, with exhaustive fault injection", async () => {
     let coinFlips;
     let rng = new ExhaustiveRNG();
-    function maybeInjectFaultWithExhaustiveRNG(functionName) {
+    let crashedProcesses = new Set();
+    function maybeInjectFaultWithExhaustiveRNG(process, functionName) {
+      assert.ok(
+        !crashedProcesses.has(process),
+        "Should not use previously-crashed process"
+      );
       // TODO(strager): Fix problems when qljs_vscode_destroy_document fails.
       if (functionName != "qljs_vscode_destroy_document") {
         let shouldCrash = rng.nextCoinFlip();
         coinFlips.push(shouldCrash);
         if (shouldCrash) {
+          crashedProcesses.add(process);
           throw new qljs.ProcessCrashed("(injected fault)");
         }
       }
@@ -362,6 +376,8 @@ describe("DocumentLinter", () => {
       console.log(`coinFlips: ${coinFlips}`);
       rng.lap();
       qljs.maybeInjectFault = originalMaybeInjectFault;
+
+      crashedProcesses.clear(); // Avoid out-of-memory errors.
     }
   });
 });