feat: implement liquid and echo tags, see #428

src/tokens/liquid-tag-token.ts

@@ -0,0 +1,33 @@
+import { DelimitedToken } from './delimited-token'
+import { TokenizationError } from '../util/error'
+import { NormalizedFullOptions } from '../liquid-options'
+import { TokenKind } from '../parser/token-kind'
+import { Tokenizer } from '../parser/tokenizer'
+
+export class LiquidTagToken extends DelimitedToken {
+  public name: string
+  public args: string
+  public constructor (
+    input: string,
+    begin: number,
+    end: number,
+    options: NormalizedFullOptions,
+    file?: string
+  ) {
+    const value = input.slice(begin, end)
+    super(TokenKind.Tag, value, input, begin, end, false, false, file)
+
+    if (!/\S/.test(value)) {
+      // A line that contains only whitespace.
+      this.name = ''
+      this.args = ''
+    } else {
+      const tokenizer = new Tokenizer(this.content, options.operatorsTrie)
+      this.name = tokenizer.readIdentifier().getText()
+      if (!this.name) throw new TokenizationError(`illegal liquid tag syntax`, this)
+
+      tokenizer.skipBlank()
+      this.args = tokenizer.remaining()
+    }
+  }
+}