feat(yield): add yield tag

fixtures/yield-fallback/compiled.js

@@ -0,0 +1,10 @@
+(function (template, ctx) {
+  let out = ''
+  if(ctx.resolve('username')) {
+    out += ctx.resolve('username')
+  } else {
+    out += '  Hello guest'
+    out += '\n'
+  }
+  return out
+})(template, ctx)

fixtures/yield-fallback/index.edge

@@ -0,0 +1,3 @@
+@yield(username)
+  Hello guest
+@endyield

fixtures/yield-fallback/index.json

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

fixtures/yield-fallback/index.txt

@@ -0,0 +1 @@
+Hello guest

fixtures/yield-html/compiled.js

@@ -0,0 +1,8 @@
+(function (template, ctx) {
+  let out = ''
+  if(ctx.resolve('greeting')) {
+    out += ctx.resolve('greeting')
+  } else {
+  }
+  return out
+})(template, ctx)

fixtures/yield-html/index.edge

@@ -0,0 +1 @@
+@!yield(greeting)

fixtures/yield-html/index.json

@@ -0,0 +1,3 @@
+{
+  "greeting": "Hello <strong>virk</strong>"
+}

fixtures/yield-html/index.txt

@@ -0,0 +1 @@
+Hello <strong>virk</strong>

fixtures/yield-tag/compiled.js

@@ -0,0 +1,8 @@
+(function (template, ctx) {
+  let out = ''
+  if(ctx.resolve('username')) {
+    out += ctx.resolve('username')
+  } else {
+  }
+  return out
+})(template, ctx)

fixtures/yield-tag/index.edge

@@ -0,0 +1 @@
+@!yield(username)

fixtures/yield-tag/index.json

@@ -0,0 +1,3 @@
+{
+  "username": "virk"
+}

fixtures/yield-tag/index.txt

@@ -0,0 +1 @@
+virk

src/Tags/Yield.ts

@@ -0,0 +1,58 @@
+/*
+* 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 { allowExpressions } from '../utils'
+
+export class YieldTag {
+  public static block = true
+  public static seekable = true
+  public static selfclosed = true
+  public static tagName = 'if'
+
+  /**
+   * Expressions which are not allowed by the sequence
+   * expression
+   *
+   * @type {Array}
+   */
+  private static allowedExpressions = ['Identifier', 'Literal', 'MemberExpression', 'CallExpression']
+
+  /**
+   * Compiles the if block node to a Javascript if statement
+   */
+  public static compile (parser: Parser, buffer: EdgeBuffer, token: IBlockNode) {
+    const parsed = parser.parseJsArg(token.properties.jsArg, token.lineno)
+    allowExpressions('yield', parsed, this.allowedExpressions)
+
+    /**
+     * Start if block
+     */
+    const parsedString = parser.statementToString(parsed)
+
+    /**
+     * If main content is truthy
+     */
+    buffer.writeStatement(`if(${parsedString}) {`)
+    buffer.indent()
+    buffer.writeLine(parsedString)
+    buffer.dedent()
+    buffer.writeStatement('} else {')
+
+    /**
+     * Else write fallback
+     */
+    buffer.indent()
+    token.children.forEach((child, index) => (parser.processToken(child, buffer)))
+    buffer.dedent()
+    buffer.writeStatement('}')
+  }
+}

src/Tags/index.ts

@@ -17,3 +17,4 @@ export { SlotTag as slot } from './Slot'
 export { DebuggerTag as debugger } from './Debugger'
 export { SetTag as set } from './Set'
 export { UnlessTag as unless } from './Unless'
+export { YieldTag as yield } from './Yield'