added constants #38

src/filtrex.d.ts

@@ -66,6 +66,16 @@ export interface Options
         [T: string]: Function
     }
 
+    /**
+     * Pass constants like `pi` or `true` to the expression without having to modify data.
+     * These constants will shadow identically named properties on the data object. In order
+     * to access `data.pi` instead of `constants.pi`, for example, use a single-quoted
+     * symbol in your expression, ie. `'pi'` instead of just `pi`.
+     */
+    constants?: {
+        [T: string]: any
+    }
+
     /**
      * If you want to do some more magic with your expression, you can supply a custom function
      * that will resolve the identifiers used in the expression and assign them a value yourself.

src/filtrex.mjs

@@ -56,7 +56,7 @@ const std =
             }
         }
 
-        return JSON.stringify(built)
+        return built
     },
 
     reduceRelation(arr) {
@@ -100,12 +100,12 @@ export function compileExpression(expression, options) {
     if (arguments.length > 2) throw new TypeError('Too many arguments.')
 
     options = typeof options === "object" ? options : {}
-    let {extraFunctions, customProp, operators} = options
+
+    const knownOptions = ['extraFunctions', 'constants', 'customProp', 'operators']
+    let {extraFunctions, constants, customProp, operators} = options
+
     for (const key of Object.keys(options))
-    {
-        if (!(["extraFunctions", "customProp", "operators"].includes(key)))
-            throw new UnknownOptionError(key)
-    }
+        if (!knownOptions.includes(key)) throw new UnknownOptionError(key)
 
 
 
@@ -160,6 +160,8 @@ export function compileExpression(expression, options) {
 
     operators = defaultOperators
 
+    constants = constants ?? {}
+
 
 
     // Compile the expression
@@ -171,35 +173,42 @@ export function compileExpression(expression, options) {
 
     // Metaprogramming functions
 
-    function prop(name, obj) {
-        if (hasOwnProperty(obj||{}, name))
+    function nakedProp(name, obj) {
+        if (hasOwnProperty(obj ?? {}, name))
             return obj[name]
 
         throw new UnknownPropertyError(name)
     }
 
     function safeGetter(obj) {
         return function get(name) {
-            if (hasOwnProperty(obj||{}, name))
+            if (hasOwnProperty(obj ?? {}, name))
                 return obj[name]
 
             throw new UnknownPropertyError(name)
         }
     }
 
     if (typeof customProp === 'function') {
-        prop = (name, obj) => customProp(name, safeGetter(obj), obj)
+        nakedProp = (name, obj) => customProp(name, safeGetter(obj), obj)
     }
 
     function createCall(fns) {
-        return function call(name, ...args) {
+        return function call({ name }, ...args) {
             if (hasOwnProperty(fns, name) && typeof fns[name] === "function")
                 return fns[name](...args)
 
             throw new UnknownFunctionError(name)
         }
     }
 
+    function prop({ name, type }, obj) {
+        if (type === 'unescaped' && hasOwnProperty(constants, name))
+            return constants[name]
+
+        return nakedProp(name, obj)
+    }
+
 
 
     // Patch together and return

src/generateParser.mjs

@@ -40,17 +40,23 @@ const grammar = {
             [_`[0-9]+(?:\.[0-9]+)?(?![0-9\.])`, `return "Number";`], // 212.321
 
             [_`[a-zA-Z$_][\.a-zA-Z0-9$_]*`,
-                `yytext = JSON.stringify(yytext);
+                `yytext = JSON.stringify({
+                    name: yytext,
+                    type: 'unescaped'
+                });
                 return "Symbol";`
             ], // some.Symbol22
 
             [_`'(?:\\'|\\\\|[^'\\])*'`,
-                `yytext = yy.buildString("'", yytext);
+                `yytext = JSON.stringify({
+                    name: yy.buildString("'", yytext),
+                    type: 'single-quoted'
+                });
                 return "Symbol";`
             ], // 'any \'escaped\' symbol'
 
             [_`"(?:\\"|\\\\|[^"\\])*"`,
-                `yytext = yy.buildString('"', yytext);
+                `yytext = JSON.stringify(yy.buildString('"', yytext));
                 return "String";`
             ], // "any \"escaped\" string"
 

test/misc.js

@@ -160,4 +160,32 @@ describe('Various other things', () => {
         expect( eval('4 + 3 not in (6, 8)') ).equals(true);
     })
 
+    it('constants basics', () => {
+        const options = { constants: { pi: Math.PI, true: true, false: false }}
+
+        expect(
+            compileExpression('2 * pi * radius', options)({ radius: 6 })
+        ).equals(2 * Math.PI * 6)
+
+        expect(
+            compileExpression('not true == false and not false == true', options)()
+        ).equals(true)
+
+        expect(
+            compileExpression('pi', options)({ pi: 3 })
+        ).equals(Math.PI)
+
+        expect(
+            compileExpression(`'pi'`, options)({ pi: 3 })
+        ).equals(3)
+
+
+        const options2 = { constants: { a: "a_const " } }
+        const data = { a: "a_data ", b: "b_data " }
+        const expr = `'a' + a + 'b' + b`
+
+        expect( compileExpression(expr, options2)(data) ).equals("a_data a_const b_data b_data ")
+
+    })
+
 });