feat: add support for regexp

src/lexer.ts

@@ -279,7 +279,12 @@ export class JsonTemplateLexer {
       };
     }
 
-    const token = this.scanPunctuator() ?? this.scanID() ?? this.scanString() ?? this.scanInteger();
+    const token =
+      this.scanRegularExpressions() ??
+      this.scanPunctuator() ??
+      this.scanID() ??
+      this.scanString() ??
+      this.scanInteger();
     if (token) {
       return token;
     }
@@ -314,7 +319,8 @@ export class JsonTemplateLexer {
       token.type === TokenType.FLOAT ||
       token.type === TokenType.STR ||
       token.type === TokenType.NULL ||
-      token.type === TokenType.UNDEFINED
+      token.type === TokenType.UNDEFINED ||
+      token.type === TokenType.REGEXP
     );
   }
 
@@ -541,7 +547,7 @@ export class JsonTemplateLexer {
         };
       }
     } else if (ch1 === '=') {
-      if ('^$*'.indexOf(ch2) >= 0) {
+      if ('^$*~'.indexOf(ch2) >= 0) {
         this.idx += 2;
         return {
           type: TokenType.PUNCT,
@@ -638,6 +644,56 @@ export class JsonTemplateLexer {
     }
   }
 
+  private static isValidRegExp(regexp: string, modifiers: string) {
+    try {
+      RegExp(regexp, modifiers);
+      return true;
+    } catch (e) {
+      return false;
+    }
+  }
+
+  private getRegExpModifiers(): string {
+    let modifiers = '';
+    while ('gimsuyv'.includes(this.codeChars[this.idx])) {
+      modifiers += this.codeChars[this.idx];
+      this.idx++;
+    }
+    return modifiers;
+  }
+
+  private scanRegularExpressions(): Token | undefined {
+    const start = this.idx;
+    const ch1 = this.codeChars[this.idx];
+
+    if (ch1 === '/') {
+      let end = this.idx + 1;
+      while (end < this.codeChars.length) {
+        if (this.codeChars[end] === '\n') {
+          return;
+        }
+        if (this.codeChars[end] === '/') {
+          break;
+        }
+        end++;
+      }
+
+      if (end < this.codeChars.length) {
+        this.idx = end + 1;
+        const regexp = this.getCode(start + 1, end);
+        const modifiers = this.getRegExpModifiers();
+        if (!JsonTemplateLexer.isValidRegExp(regexp, modifiers)) {
+          JsonTemplateLexer.throwError("invalid regular expression '%0'", regexp);
+        }
+        return {
+          type: TokenType.REGEXP,
+          value: this.getCode(start, this.idx),
+          range: [start, this.idx],
+        };
+      }
+    }
+  }
+
   private scanPunctuator(): Token | undefined {
     return (
       this.scanPunctuatorForDots() ??

src/operators.ts

@@ -74,6 +74,9 @@ export const binaryOperators = {
 
   '=$': (val1, val2): string => endsWith(val2, val1),
 
+  '=~': (val1, val2): string =>
+    `(${val2} instanceof RegExp) ? (${val2}.test(${val1})) : (${val1}==${val2})`,
+
   contains: containsStrict,
 
   '==*': (val1, val2): string => containsStrict(val2, val1),

src/parser.ts

@@ -682,6 +682,7 @@ export class JsonTemplateParser {
       this.lexer.match('$=') ||
       this.lexer.match('=$') ||
       this.lexer.match('==*') ||
+      this.lexer.match('=~') ||
       this.lexer.match('=*')
     ) {
       return {
@@ -690,7 +691,6 @@ export class JsonTemplateParser {
         args: [expr, this.parseEqualityExpr()],
       };
     }
-
     return expr;
   }
 

src/translator.ts

@@ -705,6 +705,9 @@ export class JsonTemplateTranslator {
     if (type === TokenType.STR) {
       return escapeStr(val);
     }
+    if (type === TokenType.REGEXP) {
+      return val;
+    }
     return String(val);
   }
 

src/types.ts

@@ -35,6 +35,7 @@ export enum TokenType {
   THROW = 'throw',
   KEYWORD = 'keyword',
   EOT = 'eot',
+  REGEXP = 'regexp',
 }
 
 // In the order of precedence

test/scenarios/bad_templates/bad_regex.jt

@@ -0,0 +1 @@
+/?/

test/scenarios/bad_templates/data.ts

@@ -25,6 +25,10 @@ export const data: Scenario[] = [
     templatePath: 'bad_number.jt',
     error: 'Unexpected token',
   },
+  {
+    templatePath: 'bad_regex.jt',
+    error: 'invalid regular expression',
+  },
   {
     templatePath: 'bad_string.jt',
     error: 'Unexpected end of template',

test/scenarios/comparisons/data.ts

@@ -35,6 +35,8 @@ export const data: Scenario[] = [
       true,
       true,
       true,
+      true,
+      true,
     ],
   },
 ];

test/scenarios/comparisons/template.jt

@@ -30,5 +30,7 @@
 "" empty true,
 "abc" empty false,
 ["c", "a"] subsetof ["a", "b", "c"],
-[] subsetof ["a", "b", "c"]
+[] subsetof ["a", "b", "c"],
+"abc" =~ /a.*c/,
+"AdC" =~ /a.*c/i,
 ]