Lua: Set string as metatable of string values, allowing for strVal:upper() style invocations

common/space_lua/eval.ts

@@ -8,6 +8,7 @@ import { evalPromiseValues } from "$common/space_lua/util.ts";
 import {
   luaCall,
   luaEquals,
+  luaIndexValue,
   luaSet,
   type LuaStackFrame,
 } from "$common/space_lua/runtime.ts";
@@ -407,12 +408,17 @@ function evalPrefixExpression(
         );
       }
 
-      const handleFunctionCall = (prefixValue: LuaValue) => {
+      let selfArgs: LuaValue[] = [];
+
+      const handleFunctionCall = (
+        prefixValue: LuaValue,
+      ): LuaValue | Promise<LuaValue> => {
         // Special handling for f(...) - propagate varargs
         if (
           e.args.length === 1 && e.args[0].type === "Variable" &&
           e.args[0].name === "..."
         ) {
+          // TODO: Clean this up
           const varargs = env.get("...");
           const resolveVarargs = async () => {
             const resolvedVarargs = await Promise.resolve(varargs);
@@ -439,16 +445,19 @@ function evalPrefixExpression(
           }
         }
 
-        // Normal argument handling
-        let selfArgs: LuaValue[] = [];
-        if (e.name && !prefixValue.get) {
-          throw new LuaRuntimeError(
-            `Attempting to index a non-table: ${prefixValue}`,
-            sf.withCtx(e.prefix.ctx),
-          );
-        } else if (e.name) {
+        // Normal argument handling for hello:there(a, b, c) type calls
+        if (e.name) {
           selfArgs = [prefixValue];
-          prefixValue = prefixValue.get(e.name);
+          prefixValue = luaIndexValue(prefixValue, e.name, sf);
+          if (prefixValue === null) {
+            throw new LuaRuntimeError(
+              `Attempting to index a non-table: ${prefixValue}`,
+              sf.withCtx(e.prefix.ctx),
+            );
+          }
+          if (prefixValue instanceof Promise) {
+            return prefixValue.then(handleFunctionCall);
+          }
         }
         if (!prefixValue.call) {
           throw new LuaRuntimeError(
@@ -486,15 +495,49 @@ function evalMetamethod(
   ctx: ASTCtx,
   sf: LuaStackFrame,
 ): LuaValue | undefined {
-  if (left?.metatable?.has(metaMethod)) {
-    const fn = left.metatable.get(metaMethod);
+  const leftMetatable = getMetatable(left, sf);
+  const rightMetatable = getMetatable(right, sf);
+  if (leftMetatable?.has(metaMethod)) {
+    const fn = leftMetatable.get(metaMethod);
     return luaCall(fn, [left, right], ctx, sf);
-  } else if (right?.metatable?.has(metaMethod)) {
-    const fn = right.metatable.get(metaMethod);
+  } else if (rightMetatable?.has(metaMethod)) {
+    const fn = rightMetatable.get(metaMethod);
     return luaCall(fn, [left, right], ctx, sf);
   }
 }
 
+export function getMetatable(
+  value: LuaValue,
+  sf?: LuaStackFrame,
+): LuaValue | null {
+  if (value === null || value === undefined) {
+    return null;
+  }
+  if (typeof value === "string") {
+    // Add a metatable to the string value on the fly
+    if (!sf) {
+      console.warn(
+        "metatable lookup with string value but no stack frame, returning nil",
+      );
+      return null;
+    }
+    if (!sf.threadLocal.get("_GLOBAL")) {
+      console.warn(
+        "metatable lookup with string value but no _GLOBAL, returning nil",
+      );
+      return null;
+    }
+    const stringMetatable = new LuaTable();
+    stringMetatable.set("__index", sf.threadLocal.get("_GLOBAL").get("string"));
+    return stringMetatable;
+  }
+  if (value.metatable) {
+    return value.metatable;
+  } else {
+    return null;
+  }
+}
+
 // Simplified operator definitions
 const operatorsMetaMethods: Record<string, {
   metaMethod?: string;

common/space_lua/runtime.ts

@@ -1,5 +1,5 @@
 import type { ASTCtx, LuaFunctionBody } from "./ast.ts";
-import { evalStatement } from "./eval.ts";
+import { evalStatement, getMetatable } from "./eval.ts";
 import { asyncQuickSort, evalPromiseValues } from "./util.ts";
 
 export type LuaType =
@@ -383,9 +383,10 @@ export class LuaTable implements ILuaSettable, ILuaGettable {
     value: LuaValue,
     sf?: LuaStackFrame,
   ): Promise<void> | void {
-    if (this.metatable && this.metatable.has("__newindex") && !this.has(key)) {
+    const metatable = getMetatable(this, sf);
+    if (metatable && metatable.has("__newindex") && !this.has(key)) {
       // Invoke the meta table!
-      const metaValue = this.metatable.get("__newindex", sf);
+      const metaValue = metatable.get("__newindex", sf);
       if (metaValue.then) {
         // This is a promise, we need to wait for it
         return metaValue.then((metaValue: any) => {
@@ -411,37 +412,7 @@ export class LuaTable implements ILuaSettable, ILuaGettable {
   }
 
   get(key: LuaValue, sf?: LuaStackFrame): LuaValue | Promise<LuaValue> | null {
-    const value = this.rawGet(key);
-    if (value === undefined || value === null) {
-      if (this.metatable && this.metatable.has("__index")) {
-        // Invoke the meta table
-        const metaValue = this.metatable.get("__index", sf);
-        if (metaValue.then) {
-          // Got a promise, we need to wait for it
-          return metaValue.then((metaValue: any) => {
-            if (metaValue.call) {
-              return metaValue.call(sf, this, key);
-            } else if (metaValue instanceof LuaTable) {
-              return metaValue.get(key, sf);
-            } else {
-              throw new Error("Meta table __index must be a function or table");
-            }
-          });
-        } else {
-          if (metaValue.call) {
-            return metaValue.call(sf, this, key);
-          } else if (metaValue instanceof LuaTable) {
-            return metaValue.get(key, sf);
-          } else {
-            throw new Error("Meta table __index must be a function or table");
-          }
-        }
-      } else {
-        return null;
-      }
-    } else {
-      return value;
-    }
+    return luaIndexValue(this, key, sf);
   }
 
   insert(value: LuaValue, pos: number) {
@@ -483,8 +454,9 @@ export class LuaTable implements ILuaSettable, ILuaGettable {
   }
 
   async toStringAsync(): Promise<string> {
-    if (this.metatable?.has("__tostring")) {
-      const metaValue = await this.metatable.get("__tostring");
+    const metatable = getMetatable(this);
+    if (metatable && metatable.has("__tostring")) {
+      const metaValue = await metatable.get("__tostring");
       if (metaValue.call) {
         return metaValue.call(LuaStackFrame.lostFrame, this);
       } else {
@@ -515,6 +487,59 @@ export class LuaTable implements ILuaSettable, ILuaGettable {
   }
 }
 
+/**
+ * Lookup a key in a table or a metatable
+ */
+export function luaIndexValue(
+  value: LuaValue,
+  key: LuaValue,
+  sf?: LuaStackFrame,
+): LuaValue | Promise<LuaValue> | null {
+  if (value === null || value === undefined) {
+    return null;
+  }
+  // The value is a table, so we can try to get the value directly
+  if (value instanceof LuaTable) {
+    const rawValue = value.rawGet(key);
+    if (rawValue !== undefined) {
+      return rawValue;
+    }
+  }
+  // If not, let's see if the value has a metatable and if it has a __index metamethod
+  const metatable = getMetatable(value, sf);
+  if (metatable && metatable.has("__index")) {
+    // Invoke the meta table
+    const metaValue = metatable.get("__index", sf);
+    if (metaValue.then) {
+      // Got a promise, we need to wait for it
+      return metaValue.then((metaValue: any) => {
+        if (metaValue.call) {
+          return metaValue.call(sf, value, key);
+        } else if (metaValue instanceof LuaTable) {
+          return metaValue.get(key, sf);
+        } else {
+          throw new Error("Meta table __index must be a function or table");
+        }
+      });
+    } else {
+      if (metaValue.call) {
+        return metaValue.call(sf, value, key);
+      } else if (metaValue instanceof LuaTable) {
+        return metaValue.get(key, sf);
+      } else {
+        throw new Error("Meta table __index must be a function or table");
+      }
+    }
+  }
+  // If not, perhaps let's assume this is a plain JavaScript object and we just index into it
+  const objValue = value[key];
+  if (objValue === undefined || objValue === null) {
+    return null;
+  } else {
+    return objValue;
+  }
+}
+
 export type LuaLValueContainer = { env: ILuaSettable; key: LuaValue };
 
 export async function luaSet(
@@ -576,6 +601,8 @@ export function luaLen(obj: any): number {
     return obj.length;
   } else if (Array.isArray(obj)) {
     return obj.length;
+  } else if (typeof obj === "string") {
+    return obj.length;
   } else {
     return 0;
   }

common/space_lua/stdlib/string_test.lua

@@ -14,6 +14,10 @@ assert(string.sub("Hello", 2, 4) == "ell")
 assert(string.upper("Hello") == "HELLO")
 assert(string.lower("Hello") == "hello")
 
+-- Invoke string metatable methods
+assertEqual(("hello"):len(), 5)
+assertEqual(("hello"):upper(), "HELLO")
+
 -- Test string.gsub with various replacement types
 -- Simple string replacement
 local result, count = string.gsub("hello world", "hello", "hi")
@@ -79,7 +83,6 @@ assertEqual(m2, "ello")
 -- Test with pattern with character class
 assertEqual(string.match("c", "[abc]"), "c")
 
-
 -- Test match with init position - need to capture the group
 local initMatch = string.match("hello world", "(world)", 7)
 assertEqual(initMatch, "world")

common/space_lua/stdlib/table.ts

@@ -75,7 +75,6 @@ export const tableApi = new LuaTable({
    * @returns The keys of the table.
    */
   keys: new LuaBuiltinFunction((_sf, tbl: LuaTable | LuaEnv) => {
-    console.log("Keys", tbl);
     return tbl.keys();
   }),
   /**