feat(unless): add unless tag

fixtures/unless-tag/compiled.js

@@ -0,0 +1,8 @@
+(function (template, ctx) {
+  let out = ''
+  if(!ctx.resolve('username')) {
+    out += '  Hello Guest'
+    out += '\n'
+  }
+  return out
+})(template, ctx)

fixtures/unless-tag/index.edge

@@ -0,0 +1,3 @@
+@unless(username)
+  Hello Guest
+@endunless

fixtures/unless-tag/index.json

@@ -0,0 +1,2 @@
+{
+}

fixtures/unless-tag/index.txt

@@ -0,0 +1 @@
+Hello Guest

src/Tags/Unless.ts

@@ -0,0 +1,63 @@
+/*
+* edge
+*
+* (c) Harminder Virk <virk@adonisjs.com>
+*
+* For the full copyright and license information, please view the LICENSE
+* file that was distributed with this source code.
+*/
+
+import { Parser } from 'edge-parser'
+import { EdgeBuffer } from 'edge-parser/build/src/EdgeBuffer'
+import { IBlockNode } from 'edge-lexer/build/src/Contracts'
+import { disAllowExpressions } from '../utils'
+
+export class UnlessTag {
+  public static block = true
+  public static seekable = true
+  public static selfclosed = false
+  public static tagName = 'unless'
+
+  /**
+   * Expressions which are not allowed by the sequence
+   * expression
+   *
+   * @type {Array}
+   */
+  protected bannedExpressions = ['SequenceExpression']
+
+  /**
+   * Compiles the if block node to a Javascript if statement
+   */
+  public compile (parser: Parser, buffer: EdgeBuffer, token: IBlockNode) {
+    const parsed = parser.parseJsArg(token.properties.jsArg, token.lineno)
+    disAllowExpressions('unless', parsed, this.bannedExpressions)
+
+    /**
+     * Start if block
+     */
+    buffer.writeStatement(`if(!${parser.statementToString(parsed)}) {`)
+
+    /**
+     * Indent upcoming code
+     */
+    buffer.indent()
+
+    /**
+     * Process of all kids recursively
+     */
+    token.children.forEach((child, index) => {
+      parser.processToken(child, buffer)
+    })
+
+    /**
+     * Remove identation
+     */
+    buffer.dedent()
+
+    /**
+     * Close if block
+     */
+    buffer.writeStatement('}')
+  }
+}

src/Tags/index.ts

@@ -16,3 +16,4 @@ export { ComponentTag as component } from './Component'
 export { SlotTag as slot } from './Slot'
 export { DebuggerTag as debugger } from './Debugger'
 export { SetTag as set } from './Set'
+export { UnlessTag as unless } from './Unless'