feat: debug traceback

.vscode/settings.json

@@ -24,6 +24,7 @@
         "chunkname",
         "cmodule",
         "createtable",
+        "currentline",
         "cwrap",
         "emscripten",
         "emsdk",
@@ -48,12 +49,16 @@
         "getupvalue",
         "GLOBALSINDEX",
         "gsub",
+        "HEAPU",
+        "IDSIZE",
         "iscfunction",
         "istable",
         "isuserdata",
+        "lastlinedefined",
         "lessthan",
         "liblua",
         "libname",
+        "linedefined",
         "loadbuffer",
         "loadfile",
         "loadfilex",
@@ -65,6 +70,7 @@
         "metatable",
         "multireturn",
         "MULTRET",
+        "namewhat",
         "nargs",
         "narr",
         "newindex",
@@ -75,6 +81,7 @@
         "nofix",
         "nrec",
         "nresults",
+        "nups",
         "objindex",
         "objlen",
         "openlibs",
@@ -123,7 +130,10 @@
         "topointer",
         "tothread",
         "touserdata",
+        "traceback",
+        "tracebacks",
         "typerror",
+        "upvalue",
         "upvalueindex",
         "wasmoon",
         "xmove"

build.sh

@@ -27,7 +27,8 @@ emcc \
         'setValue', \
         'lengthBytesUTF8', \
         'stringToUTF8', \
-        'stringToNewUTF8'
+        'stringToNewUTF8', \
+        'UTF8ToString'
     ]" \
     -s INCOMING_MODULE_JS_API="[
         'locateFile', \

src/definitions.ts

@@ -5,6 +5,8 @@ export const LUA_REGISTRYINDEX = -10000;
 export const LUA_ENVIRONINDEX = -10001;
 export const LUA_GLOBALSINDEX = -10002;
 
+export const LUA_IDSIZE = 60;
+
 export enum LuaReturn {
     Ok = 0,
     Yield = 1,

src/lua-debug.ts

@@ -0,0 +1,81 @@
+import { LUA_IDSIZE } from './definitions';
+
+interface LuaDebugTraceback {
+    event: number;
+    name: string;
+    namewhat: string;
+    what: string;
+    source: string;
+    currentline: number | '?';
+    nups: number;
+    linedefined: number | '?';
+    lastlinedefined: number | '?';
+    short_src: string;
+    i_ci: number;
+}
+
+export class LuaDebug {
+    public static readonly structSize = 100;
+    private pointer: number;
+    private module: LuaEmscriptenModule;
+    private tracebacks: LuaDebugTraceback[] = [];
+    private message: string;
+
+    constructor(pointer: number, module: LuaEmscriptenModule, message: string) {
+        this.pointer = pointer;
+        this.module = module;
+        this.message = message;
+    }
+
+    public read(): void {
+        let baseIndex = this.pointer >> 2;
+        const event = this.module.HEAPU32.at(baseIndex++) as number;
+        const name = this.readStructString(baseIndex++);
+        const namewhat = this.readStructString(baseIndex++);
+        const what = this.readStructString(baseIndex++);
+        const source = this.readStructString(baseIndex++);
+        const currentline = this.module.HEAPU32.at(baseIndex++) as number;
+        const nups = this.module.HEAPU32.at(baseIndex++) as number;
+        const linedefined = this.module.HEAPU32.at(baseIndex++) as number;
+        const lastlinedefined = this.module.HEAPU32.at(baseIndex++) as number;
+        const short_src = this.module.UTF8ToString(baseIndex << 2, 60);
+        const i_ci = this.module.HEAPU32.at(baseIndex + LUA_IDSIZE / 4) as number;
+
+        const traceback: LuaDebugTraceback = {
+            event,
+            name: name || '?',
+            namewhat,
+            what,
+            source,
+            currentline: currentline === 0xffffffff ? '?' : currentline,
+            nups,
+            linedefined: linedefined === 0xffffffff ? '?' : linedefined,
+            lastlinedefined: lastlinedefined === 0xffffffff ? '?' : lastlinedefined,
+            short_src,
+            i_ci,
+        };
+        this.tracebacks.push(traceback);
+    }
+
+    public getMessage(): string {
+        const result: string[] = [];
+        result.push(`${this.tracebacks[0]?.short_src || '?'}:${this.tracebacks[0]?.currentline || '?'}: ${this.message}`);
+        if (this.tracebacks.length) {
+            result.push('stack traceback:');
+        }
+        for (const traceback of this.tracebacks) {
+            result.push(
+                `    at ${traceback.name} (${traceback.short_src}:${traceback.currentline}) (${traceback.what}:${traceback.namewhat})`,
+            );
+        }
+        return result.join('\n');
+    }
+
+    public getTracebacks(): LuaDebugTraceback[] {
+        return this.tracebacks;
+    }
+
+    private readStructString(structPointer: number): string {
+        return this.module.UTF8ToString(this.module.HEAPU32.at(structPointer) as number);
+    }
+}

src/thread.ts

@@ -1,6 +1,7 @@
 import * as lodash from 'lodash';
 import { JsType } from './type-bind';
 import { LUA_MULTRET, LUA_REGISTRYINDEX, LuaEventMasks, LuaReturn, LuaType, PointerSize } from './definitions';
+import { LuaDebug } from './lua-debug';
 import { getTable } from './table';
 import MultiReturn from './multireturn';
 import Pointer from './utils/pointer';
@@ -430,6 +431,24 @@ export default class LuaThread {
                 }
             }
 
+            if (result !== LuaReturn.ErrorMem) {
+                const pointer = this.luaApi.module._malloc(LuaDebug.structSize);
+                try {
+                    let level = 0;
+                    const luaDebug = new LuaDebug(pointer, this.luaApi.module, error.message);
+                    while (this.luaApi.lua_getstack(this.address, level, pointer)) {
+                        this.luaApi.lua_getinfo(this.address, 'nSlu', pointer);
+                        luaDebug.read();
+                        level++;
+                    }
+                    error.message = luaDebug.getMessage();
+                } catch (err) {
+                    console.warn('Error in generate stack trace', err);
+                } finally {
+                    this.luaApi.module._free(pointer);
+                }
+            }
+
             throw error;
         }
     }

test/debug.mjs

@@ -2,12 +2,11 @@ import { Lua } from '../dist/index.js';
 // This file was created as a sandbox to test and debug on vscode
 
 const lua = await Lua.create();
-
-const obj = {};
-lua.ctx.obj = obj;
-
-const o = lua.ctx.obj;
-o.name = 23333;
-console.log(o.name);
-
-lua.doStringSync('print(obj.name)');
+await lua.doString(
+    `local function a()
+error("function a threw error")
+end
+local function b() a() end
+local function c() b() end
+c()`,
+);

test/engine.test.js

@@ -613,13 +613,12 @@ describe('Engine', () => {
             `);
             throw new Error('should not be reached');
         } catch (err) {
-            expect(err.message).to.includes('[string "..."]:3: function a threw error');
-            // TODO: stack traceback
-            // expect(err.message).to.includes('stack traceback:');
-            // expect(err.message).to.includes(`[string "..."]:3: in upvalue 'a'`);
-            // expect(err.message).to.includes(`[string "..."]:5: in upvalue 'b'`);
-            // expect(err.message).to.includes(`[string "..."]:6: in local 'c'`);
-            // expect(err.message).to.includes(`[string "..."]:7: in main chunk`);
+            expect(err.message).to.includes('at error ([C]:?) (C:global)');
+            expect(err.message).to.includes('stack traceback:');
+            expect(err.message).to.includes(`at a ([string "..."]:3) (Lua:upvalue)`);
+            expect(err.message).to.includes(`at b ([string "..."]:5) (Lua:upvalue)`);
+            expect(err.message).to.includes(`at c ([string "..."]:6) (Lua:local)`);
+            expect(err.message).to.includes(`at ? ([string "..."]:7) (main:)`);
         }
     });
 

types/wasm.d.ts

@@ -8,8 +8,10 @@ interface LuaEmscriptenModule extends EmscriptenModule {
     stringToNewUTF8: typeof allocateUTF8;
     lengthBytesUTF8: typeof lengthBytesUTF8;
     stringToUTF8: typeof stringToUTF8;
+    UTF8ToString: typeof UTF8ToString;
     ENV: EnvironmentVariables;
     _realloc: (pointer: number, size: number) => number;
+    _malloc: (size: number) => number;
 }
 
 interface ReferenceMetadata {