feat(HtmlLexer): allow "<" in text tokens

fixes #5550

modules/angular2/test/compiler/html_lexer_spec.ts

@@ -192,15 +192,6 @@ export function main() {
             ]);
       });
 
-      it('should report missing name after <', () => {
-        expect(tokenizeAndHumanizeErrors('<'))
-            .toEqual([[HtmlTokenType.TAG_OPEN_START, 'Unexpected character "EOF"', '0:1']]);
-      });
-
-      it('should report missing >', () => {
-        expect(tokenizeAndHumanizeErrors('<name'))
-            .toEqual([[HtmlTokenType.TAG_OPEN_START, 'Unexpected character "EOF"', '0:5']]);
-      });
     });
 
     describe('attributes', () => {
@@ -335,20 +326,6 @@ export function main() {
             ]);
       });
 
-      it('should report missing value after =', () => {
-        expect(tokenizeAndHumanizeErrors('<name a='))
-            .toEqual([[HtmlTokenType.ATTR_VALUE, 'Unexpected character "EOF"', '0:8']]);
-      });
-
-      it('should report missing end quote for \'', () => {
-        expect(tokenizeAndHumanizeErrors('<name a=\''))
-            .toEqual([[HtmlTokenType.ATTR_VALUE, 'Unexpected character "EOF"', '0:9']]);
-      });
-
-      it('should report missing end quote for "', () => {
-        expect(tokenizeAndHumanizeErrors('<name a="'))
-            .toEqual([[HtmlTokenType.ATTR_VALUE, 'Unexpected character "EOF"', '0:9']]);
-      });
     });
 
     describe('closing tags', () => {
@@ -448,6 +425,36 @@ export function main() {
         expect(tokenizeAndHumanizeSourceSpans('a'))
             .toEqual([[HtmlTokenType.TEXT, 'a'], [HtmlTokenType.EOF, '']]);
       });
+
+      it('should allow "<" in text nodes', () => {
+        expect(tokenizeAndHumanizeParts('{{ a < b ? c : d }}'))
+            .toEqual([[HtmlTokenType.TEXT, '{{ a < b ? c : d }}'], [HtmlTokenType.EOF]]);
+
+        expect(tokenizeAndHumanizeSourceSpans('<p>a<b</p>'))
+            .toEqual([
+              [HtmlTokenType.TAG_OPEN_START, '<p'],
+              [HtmlTokenType.TAG_OPEN_END, '>'],
+              [HtmlTokenType.TEXT, 'a<b'],
+              [HtmlTokenType.TAG_CLOSE, '</p>'],
+              [HtmlTokenType.EOF, ''],
+            ]);
+      });
+
+      // TODO(vicb): make the lexer aware of Angular expressions
+      // see https://github.com/angular/angular/issues/5679
+      it('should parse valid start tag in interpolation', () => {
+        expect(tokenizeAndHumanizeParts('{{ a <b && c > d }}'))
+            .toEqual([
+              [HtmlTokenType.TEXT, '{{ a '],
+              [HtmlTokenType.TAG_OPEN_START, null, 'b'],
+              [HtmlTokenType.ATTR_NAME, null, '&&'],
+              [HtmlTokenType.ATTR_NAME, null, 'c'],
+              [HtmlTokenType.TAG_OPEN_END],
+              [HtmlTokenType.TEXT, ' d }}'],
+              [HtmlTokenType.EOF]
+            ]);
+      });
+
     });
 
     describe('raw text', () => {