enh(handlebars) Support for sub-expressions, path-expressions, hashes…

…, block-parameters and literals (#2344)

- `htmlbars` grammar is now deprecated. Use `handlebars` instead.

A stub is included so that anyone literally referencing the old `htmlbars` file (say manually requiring it in Node.js, etc) is still covered, but everyone should transition to `handlebars` now.

CHANGES.md

@@ -13,6 +13,7 @@ Parser Engine:
 
 Deprecations:
 
+- `htmlbars` grammar is now deprecated. Use `handlebars` instead. (#2344) [Nils Knappmeier][]
 - when using `highlightBlock` `result.re` deprecated. Use `result.relevance` instead. (#2552) [Josh Goebel][]
 - ditto for `result.second_best.re` => `result.second_best.relevance` (#2552)
 - `lexemes` is now deprecated in favor of `keywords.$pattern` key (#2519) [Josh Goebel][]
@@ -37,6 +38,7 @@ Language Improvements:
 - fix(swift) `@objcMembers` was being partially highlighted (#2543) [Nick Randall][]
 - enh(dart) Add `late` and `required` keywords, and `Never` built-in type (#2550) [Sam Rawlins][]
 - enh(erlang) Add underscore separators to numeric literals (#2554) [Sergey Prokhorov][]
+- enh(handlebars) Support for sub-expressions, path-expressions, hashes, block-parameters and literals (#2344) [Nils Knappmeier][]
 
 [Josh Goebel]: https://github.com/yyyc514
 [Peter Plantinga]: https://github.com/pplantinga
@@ -46,6 +48,7 @@ Language Improvements:
 [Nick Randall]: https://github.com/nicked
 [Sam Rawlins]: https://github.com/srawlins
 [Sergey Prokhorov]: https://github.com/seriyps
+[Nils Knappmeier]: https://github.com/nknapp
 
 
 ## Version 10.0.2

src/languages/handlebars.js

@@ -7,38 +7,183 @@ Website: https://handlebarsjs.com
 Category: template
 */
 
+import * as regex from '../lib/regex'
+
 export default function(hljs) {
-  var BUILT_INS = {'builtin-name': 'each in with if else unless bindattr action collection debugger log outlet template unbound view yield lookup'};
+  const BUILT_INS = {
+    'builtin-name': [
+      'action',
+      'bindattr',
+      'collection',
+      'component',
+      'concat',
+      'debugger',
+      'each',
+      'each-in',
+      'get',
+      'hash',
+      'if',
+      'in',
+      'input',
+      'link-to',
+      'loc',
+      'log',
+      'lookup',
+      'mut',
+      'outlet',
+      'partial',
+      'query-params',
+      'render',
+      'template',
+      'textarea',
+      'unbound',
+      'unless',
+      'view',
+      'with',
+      'yield'
+    ].join(" ")
+  };
 
-  var IDENTIFIER_PLAIN_OR_QUOTED = {
-    begin: /".*?"|'.*?'|\[.*?\]|\w+/
+  const LITERALS = {
+    literal: [
+      'true',
+      'false',
+      'undefined',
+      'null'
+    ].join(" ")
   };
 
-  var EXPRESSION_OR_HELPER_CALL = hljs.inherit(IDENTIFIER_PLAIN_OR_QUOTED, {
-    keywords: BUILT_INS,
+  // as defined in https://handlebarsjs.com/guide/expressions.html#literal-segments
+  // this regex matches literal segments like ' abc ' or [ abc ] as well as helpers and paths
+  // like a/b, ./abc/cde, and abc.bcd
+
+  const DOUBLE_QUOTED_ID_REGEX=/".*?"/;
+  const SINGLE_QUOTED_ID_REGEX=/'.*?'/;
+  const BRACKET_QUOTED_ID_REGEX=/\[.*?\]/;
+  const PLAIN_ID_REGEX=/[^\s!"#%&'()*+,.\/;<=>@\[\\\]^`{|}~]+/;
+  const PATH_DELIMITER_REGEX=/\.|\//;
+
+  const IDENTIFIER_REGEX = regex.concat(
+    '(',
+    SINGLE_QUOTED_ID_REGEX, '|',
+    DOUBLE_QUOTED_ID_REGEX, '|',
+    BRACKET_QUOTED_ID_REGEX, '|',
+    PLAIN_ID_REGEX, '|',
+    PATH_DELIMITER_REGEX,
+    ')+'
+  );
+
+  // identifier followed by a equal-sign (without the equal sign)
+  const HASH_PARAM_REGEX = regex.concat(
+    '(',
+    BRACKET_QUOTED_ID_REGEX, '|',
+    PLAIN_ID_REGEX,
+    ')(?==)'
+  );
+
+  const HELPER_NAME_OR_PATH_EXPRESSION = {
+    begin: IDENTIFIER_REGEX,
+    lexemes: /[\w.\/]+/
+  };
+
+  const HELPER_PARAMETER = hljs.inherit(HELPER_NAME_OR_PATH_EXPRESSION, {
+    keywords: LITERALS
+  });
+
+  const SUB_EXPRESSION = {
+    begin: /\(/,
+    end: /\)/
+    // the "contains" is added below when all necessary sub-modes are defined
+  };
+
+  const HASH = {
+    // fka "attribute-assignment", parameters of the form 'key=value'
+    className: 'attr',
+    begin: HASH_PARAM_REGEX,
+    relevance: 0,
     starts: {
-      // helper params
-      endsWithParent: true,
-      relevance: 0,
-      contains: [hljs.inherit(IDENTIFIER_PLAIN_OR_QUOTED, {relevance: 0})]
+      begin: /=/,
+      end: /=/,
+      starts: {
+        contains: [
+          hljs.NUMBER_MODE,
+          hljs.QUOTE_STRING_MODE,
+          hljs.APOS_STRING_MODE,
+          HELPER_PARAMETER,
+          SUB_EXPRESSION
+        ]
+      }
     }
+  };
+
+  const BLOCK_PARAMS = {
+    // parameters of the form '{{#with x as | y |}}...{{/with}}'
+    begin: /as\s+\|/,
+    keywords: { keyword: 'as' },
+    end: /\|/,
+    contains: [
+      {
+        // define sub-mode in order to prevent highlighting of block-parameter named "as"
+        begin: /\w+/
+      }
+    ]
+  };
+
+  const HELPER_PARAMETERS = {
+    contains: [
+      hljs.NUMBER_MODE,
+      hljs.QUOTE_STRING_MODE,
+      hljs.APOS_STRING_MODE,
+      BLOCK_PARAMS,
+      HASH,
+      HELPER_PARAMETER,
+      SUB_EXPRESSION
+    ],
+    returnEnd: true
+    // the property "end" is defined through inheritance when the mode is used. If depends
+    // on the surrounding mode, but "endsWithParent" does not work here (i.e. it includes the
+    // end-token of the surrounding mode)
+  };
+
+  const SUB_EXPRESSION_CONTENTS = hljs.inherit(HELPER_NAME_OR_PATH_EXPRESSION, {
+    className: 'name',
+    keywords: BUILT_INS,
+    starts: hljs.inherit(HELPER_PARAMETERS, {
+      end: /\)/,
+    })
   });
 
-  var BLOCK_MUSTACHE_CONTENTS = hljs.inherit(EXPRESSION_OR_HELPER_CALL, {
+  SUB_EXPRESSION.contains = [
+    SUB_EXPRESSION_CONTENTS
+  ];
+
+  const OPENING_BLOCK_MUSTACHE_CONTENTS = hljs.inherit(HELPER_NAME_OR_PATH_EXPRESSION, {
+    keywords: BUILT_INS,
+    className: 'name',
+    starts: hljs.inherit(HELPER_PARAMETERS, {
+      end: /}}/,
+    })
+  });
+
+  const CLOSING_BLOCK_MUSTACHE_CONTENTS = hljs.inherit(HELPER_NAME_OR_PATH_EXPRESSION, {
+    keywords: BUILT_INS,
     className: 'name'
   });
 
-  var BASIC_MUSTACHE_CONTENTS = hljs.inherit(EXPRESSION_OR_HELPER_CALL, {
-    // relevance 0 for backward compatibility concerning auto-detection
-    relevance: 0
+  const BASIC_MUSTACHE_CONTENTS = hljs.inherit(HELPER_NAME_OR_PATH_EXPRESSION, {
+    className: 'name',
+    keywords: BUILT_INS,
+    starts: hljs.inherit(HELPER_PARAMETERS, {
+      end: /}}/,
+    })
   });
 
-  var ESCAPE_MUSTACHE_WITH_PRECEEDING_BACKSLASH = {begin: /\\\{\{/, skip: true};
-  var PREVENT_ESCAPE_WITH_ANOTHER_PRECEEDING_BACKSLASH = {begin: /\\\\(?=\{\{)/, skip: true};
+  const ESCAPE_MUSTACHE_WITH_PRECEEDING_BACKSLASH = {begin: /\\\{\{/, skip: true};
+  const PREVENT_ESCAPE_WITH_ANOTHER_PRECEEDING_BACKSLASH = {begin: /\\\\(?=\{\{)/, skip: true};
 
   return {
     name: 'Handlebars',
-    aliases: ['hbs', 'html.hbs', 'html.handlebars'],
+    aliases: ['hbs', 'html.hbs', 'html.handlebars', 'htmlbars'],
     case_insensitive: true,
     subLanguage: 'xml',
     contains: [
@@ -49,34 +194,50 @@ export default function(hljs) {
       {
         // open raw block "{{{{raw}}}} content not evaluated {{{{/raw}}}}"
         className: 'template-tag',
-        begin: /\{\{\{\{(?!\/)/, end: /\}\}\}\}/,
-        contains: [BLOCK_MUSTACHE_CONTENTS],
+        begin: /\{\{\{\{(?!\/)/,
+        end: /\}\}\}\}/,
+        contains: [OPENING_BLOCK_MUSTACHE_CONTENTS],
         starts: {end: /\{\{\{\{\//, returnEnd: true, subLanguage: 'xml'}
       },
       {
         // close raw block
         className: 'template-tag',
-        begin: /\{\{\{\{\//, end: /\}\}\}\}/,
-        contains: [BLOCK_MUSTACHE_CONTENTS]
+        begin: /\{\{\{\{\//,
+        end: /\}\}\}\}/,
+        contains: [CLOSING_BLOCK_MUSTACHE_CONTENTS]
       },
       {
         // open block statement
         className: 'template-tag',
-        begin: /\{\{[#\/]/, end: /\}\}/,
-        contains: [BLOCK_MUSTACHE_CONTENTS],
+        begin: /\{\{#/,
+        end: /\}\}/,
+        contains: [OPENING_BLOCK_MUSTACHE_CONTENTS],
+      },
+      {
+        className: 'template-tag',
+        begin: /\{\{(?=else\}\})/,
+        end: /\}\}/,
+        keywords: 'else'
+      },
+      {
+        // closing block statement
+        className: 'template-tag',
+        begin: /\{\{\//,
+        end: /\}\}/,
+        contains: [CLOSING_BLOCK_MUSTACHE_CONTENTS],
       },
       {
         // template variable or helper-call that is NOT html-escaped
         className: 'template-variable',
-        begin: /\{\{\{/, end: /\}\}\}/,
-        keywords: BUILT_INS,
+        begin: /\{\{\{/,
+        end: /\}\}\}/,
         contains: [BASIC_MUSTACHE_CONTENTS]
       },
       {
         // template variable or helper-call that is html-escaped
         className: 'template-variable',
-        begin: /\{\{/, end: /\}\}/,
-        keywords: BUILT_INS,
+        begin: /\{\{/,
+        end: /\}\}/,
         contains: [BASIC_MUSTACHE_CONTENTS]
       }
     ]