Activate no-constant-condition rule of eslint

sao/eslint.config.mjs

@@ -21,7 +21,6 @@ export default [
             },
         },
         rules: {
-            "no-constant-condition": "off",
             "no-empty": "off",
             "no-extra-boolean-cast": "off",
             "no-prototype-builtins": "off",

sao/src/common.js

@@ -1022,7 +1022,8 @@
         read_token: function() {
             var quoted = false;
             var escapedstate = ' ';
-            while (true) {
+            const always = true;
+            while (always) {
                 var nextchar = this.instream.read(1);
                 if (this.state === null) {
                     this.token = '';  // past en of file
@@ -1166,13 +1167,12 @@
             try {
                 var lex = new Sao.common.udlex(input);
                 var tokens = [];
-                while (true) {
+                do {
                     var token = lex.next();
-                    if (token === null) {
-                        break;
+                    if (token !== null) {
+                        tokens.push(token);
                     }
-                    tokens.push(token);
-                }
+                } while (token !== null);
                 tokens = this.group_operator(tokens);
                 tokens = this.parenthesize(tokens);
                 tokens = this.group(tokens);

sao/tests/sao.js

@@ -1505,13 +1505,12 @@
         var udlex = function(input) {
             var lex = new Sao.common.udlex(input);
             var tokens = [];
-            while (true) {
+            do {
                 var token = lex.next();
-                if (token === null) {
-                    break;
+                if (token !== null) {
+                    tokens.push(token);
                 }
-                tokens.push(token);
-            }
+            } while (token !== null);
             return tokens;
         };
         var c = function(clause) {