Add optional unwrap syntax

src/template/lib.zig

@@ -40,7 +40,7 @@ pub fn execute(
     args: anytype,
     context: anytype,
 ) !void {
-    @setEvalBranchQuota(@intCast(u32, template.len * 8));
+    @setEvalBranchQuota(@intCast(u32, template.len * 12));
 
     const tokens = comptime parseTemplateTokens(ControlTokenIter{ .text = template });
     const tmpl = comptime parseTemplate(tokens, 0, .root);
@@ -209,20 +209,30 @@ fn print(writer: anytype, arg: anytype) !void {
     try std.fmt.format(writer, "{}", .{arg});
 }
 
-fn Deref(comptime T: type, comptime names: []const []const u8) type {
+fn Deref(comptime T: type, comptime names: []const DerefDecl) type {
     if (names.len == 0) return T;
 
     // Compiler segfaults when I use std.meta to get this info so we search it manually
+    const F = switch (names[0]) {
+        .field => |name| blk: {
             const field = for (@typeInfo(T).Struct.fields) |f| {
-        if (std.mem.eql(u8, f.name, names[0])) break f;
+                if (std.mem.eql(u8, f.name, name)) break f;
-    } else @compileError("Unknown field " ++ names[0] ++ " in type " ++ @typeName(T));
+            } else @compileError("Unknown field " ++ name ++ " in type " ++ @typeName(T));
+            break :blk field.field_type;
+        },
+        .optional_unwrap => std.meta.Child(T),
+    };
 
-    return Deref(field.field_type, names[1..]);
+    return Deref(F, names[1..]);
 }
 
-fn deref(arg: anytype, comptime names: []const []const u8) Deref(@TypeOf(arg), names) {
+fn deref(arg: anytype, comptime names: []const DerefDecl) Deref(@TypeOf(arg), names) {
     if (names.len == 0) return arg;
-    return deref(@field(arg, names[0]), names[1..]);
+
+    switch (names[0]) {
+        .field => |name| return deref(@field(arg, name), names[1..]),
+        .optional_unwrap => return arg.?,
+    }
 }
 
 fn EvaluateExpression(
@@ -524,6 +534,7 @@ fn parseTemplateTokens(comptime tokens: ControlTokenIter) []const TemplateToken
             .open_paren => items = items ++ [_]TemplateToken{.{ .text = "(" }},
             .close_paren => items = items ++ [_]TemplateToken{.{ .text = ")" }},
             .double_quote => items = items ++ [_]TemplateToken{.{ .text = "\"" }},
+            .question_mark => items = items ++ [_]TemplateToken{.{ .text = "?" }},
         };
 
         return items;
@@ -922,23 +933,28 @@ fn parseSwitchHeader(comptime tokens: ControlTokenIter) ParseResult(ControlToken
     }
 }
 
-fn parseDeref(comptime tokens: ControlTokenIter) ParseResult(ControlTokenIter, []const []const u8) {
+fn parseDeref(comptime tokens: ControlTokenIter) ParseResult(ControlTokenIter, []const DerefDecl) {
     comptime {
         var iter = tokens;
-        var fields: []const []const u8 = &.{};
+        var fields: []const DerefDecl = &.{};
         var wants = .text;
         while (iter.peek()) |token| {
             switch (token) {
                 .whitespace => {},
                 .text => |text| {
                     if (wants == .period) break;
-                    fields = fields ++ [1][]const u8{text};
+                    fields = fields ++ [1]DerefDecl{.{ .field = text }};
                     wants = .period;
                 },
                 .period => {
                     if (wants != .period) @compileError("Unexpected token \".\"");
                     wants = .text;
                 },
+                .question_mark => {
+                    if (wants == .period) break;
+                    fields = fields ++ [1]DerefDecl{.{ .optional_unwrap = {} }};
+                    wants = .period;
+                },
                 else => if (wants == .period or fields.len == 0) break else @compileError("Unexpected token"),
             }
             _ = iter.next();
@@ -993,6 +1009,7 @@ fn parseFormat(comptime tokens: ControlTokenIter) ParseResult(ControlTokenIter,
             .percent => fmt_str = fmt_str ++ "%",
             .open_paren => fmt_str = fmt_str ++ "(",
             .close_paren => fmt_str = fmt_str ++ ")",
+            .question_mark => fmt_str = fmt_str ++ "?",
             .double_quote => break,
         };
 
@@ -1020,15 +1037,20 @@ const TemplateItem = union(enum) {
     statement: Statement,
 };
 
+const DerefDecl = union(enum) {
+    field: []const u8,
+    optional_unwrap: void,
+};
+
 const EqualsExpr = struct {
     lhs: Expression,
     rhs: Expression,
 };
 
 const Expression = union(enum) {
-    arg_deref: []const []const u8,
+    arg_deref: []const DerefDecl,
-    capture_deref: []const []const u8,
+    capture_deref: []const DerefDecl,
-    context_deref: []const []const u8,
+    context_deref: []const DerefDecl,
     equals: *const EqualsExpr,
     builtin: *const BuiltinCall,
 };
@@ -1162,6 +1184,7 @@ const ControlToken = union(enum) {
     open_paren: void,
     close_paren: void,
     double_quote: void,
+    question_mark: void,
 };
 
 const ControlTokenIter = struct {
@@ -1197,6 +1220,7 @@ const ControlTokenIter = struct {
             '(' => return .{ .open_paren = {} },
             ')' => return .{ .close_paren = {} },
             '"' => return .{ .double_quote = {} },
+            '?' => return .{ .question_mark = {} },
             ' ', '\t', '\n', '\r' => {
                 var idx: usize = 0;
                 while (idx < remaining.len and std.mem.indexOfScalar(u8, " \t\n\r", remaining[idx]) != null) : (idx += 1) {}
@@ -1208,7 +1232,7 @@ const ControlTokenIter = struct {
             },
             else => {
                 var idx: usize = 0;
-                while (idx < remaining.len and std.mem.indexOfScalar(u8, "{}.#|$/=@,%()\" \t\n\r", remaining[idx]) == null) : (idx += 1) {}
+                while (idx < remaining.len and std.mem.indexOfScalar(u8, "{}.#|$/=@,%()\"? \t\n\r", remaining[idx]) == null) : (idx += 1) {}
 
                 self.start += idx - 1;
                 return .{ .text = remaining[0..idx] };

src/template/test.tmp.html

@@ -47,6 +47,7 @@
       {#if .maybe_foo |$v|}{$v}{#else}null{/if}
       {#if .maybe_bar |$v|}{$v}{#else}null{/if}
       {#if .maybe_foo |$_|}abcd{#else}null{/if}
+      {.maybe_foo.?}
 
       <template>{#template test_tmpl .bar}</template>
       <template>{#template test_tmpl .}</template>