Sometimes failed assertion checks make it difficult to tell what went wrong. For debugging the programmer not only wants to know that a check failed, but also why it failed. This macro outputs the values of all sub-expressions.
import haxe.macro.Expr; using haxe.macro.Tools; class Assert { static public macro function assert(e:Expr) { var s = e.toString(); var p = e.pos; var el = []; var descs = []; function add(e:Expr, s:String) { var v = "_tmp" + el.length; el.push(macro var $v = $e); descs.push(s); return v; } function map(e:Expr) { return switch (e.expr) { case EConst((CInt(_) | CFloat(_) | CString(_) | CRegexp(_) | CIdent("true" | "false" | "null"))): e; case _: var s = e.toString(); e = e.map(map); macro $i{add(e, s)}; } } var e = map(e); var a = [for (i in 0...el.length) macro { expr: $v{descs[i]}, value: $i{"_tmp" + i} }]; el.push(macro if (!$e) @:pos(p) throw new Assert.AssertionFailure($v{s}, $a{a})); return macro $b{el}; } } private typedef AssertionPart = { expr: String, value: Dynamic } class AssertionFailure { public var message(default, null):String; public var parts(default, null):Array<AssertionPart>; public function new(message:String, parts:Array<AssertionPart>) { this.message = message; this.parts = parts; } public function toString() { var buf = new StringBuf(); buf.add("Assertion failure: " + message); for (part in parts) { buf.add("\n\t" + part.expr + ": " + part.value); } return buf.toString(); } }
Usage
class Main { static function main() { //Error: Assertion failure: x == 7 && y == 11 //x: 7 //x == 7: true //y: 10 //y == 11: false //x == 7 && y == 11: false var x = 7; var y = 10; Assert.assert(x == 7 && y == 11); //Error: Assertion failure: a.length > 0 //a: [] //a.length: 0 //a.length > 0: false var a = []; Assert.assert(a.length > 0); } }
Inspired by https://github.com/sconover/wrong
