feat(syntax-highlight): Add the let command, resolves #55 (#60)

syntaxes/html.json

@@ -7,6 +7,9 @@
     {
       "include": "#router-view.html.au"
     },
+    {
+      "include": "#let.html.au"
+    },    
     {
       "include": "#meta.tag.block.any.html"
     },
@@ -122,6 +125,27 @@
         "include": "#tag-stuff"
       }]
     },
+    "let.html.au": {
+      "begin": "(<\/?)((?i:let)\\b)",
+      "beginCaptures": {
+        "1": {
+          "name": "punctuation.definition.tag.begin.html"
+        },
+        "2": {
+          "name": "let.element.html.au"
+        }
+      },
+      "end": "(>)",
+      "endCaptures": {
+        "1": {
+          "name": "punctuation.definition.tag.end.html"
+        }
+      },
+      "name": "meta.tag.inline.any.html",
+      "patterns": [{
+        "include": "#tag-stuff"
+      }]
+    },    
     "meta.tag.other.html": {
       "begin": "(<\/?)([a-zA-Z0-9:\\-]+)",
       "beginCaptures": {
@@ -516,4 +540,4 @@
     }
   },
   "scopeName": "au.html"
-}
+}

test/syntax.html/let.test.ts

@@ -0,0 +1,34 @@
+import { assert } from 'chai';
+import { getTokenOnCharRange, hasScope, tokenizeLine } from './test.utils';
+
+describe('The Aurelia HTML syntax let element', () => {
+
+  it('must tokenize let start element with scope "let.element.html.au"', () => {
+
+    // arrange
+    let scope = 'let.element.html.au';
+
+    // act
+    let lineToken = tokenizeLine('<let>');
+
+    // assert
+    let token = getTokenOnCharRange(lineToken, 1, 4);
+    assert.isOk(hasScope(token.scopes, scope));
+
+  });
+
+  it('must tokenize let end element with scope "let.element.html.au"', () => {
+
+    // arrange
+    let scope = 'let.element.html.au';
+
+    // act
+    let lineToken = tokenizeLine('</let>');
+
+    // assert
+    let token = getTokenOnCharRange(lineToken, 2, 5);
+    assert.isOk(hasScope(token.scopes, scope));
+
+  });
+
+});