feat: implement add emit declaration

transformations/__tests__/add-emit-declaration.spec.ts

@@ -0,0 +1,81 @@
+import { defineInlineTest } from 'jscodeshift/src/testUtils'
+const transform = require('../add-emit-declaration')
+
+defineInlineTest(
+  transform,
+  {},
+  `export default {
+  props: ['text'],
+  methods: {
+    input: function() {
+      this.$emit('increment')
+      this.$emit('decrement')
+    }
+  }
+}`,
+  `export default {
+  emits: ["increment", "decrement"],
+  props: ['text'],
+
+  methods: {
+    input: function() {
+      this.$emit('increment')
+      this.$emit('decrement')
+    }
+  }
+};`,
+  'add emit declaration'
+)
+
+defineInlineTest(
+  transform,
+  {},
+  `export default {
+  emits: [],
+  props: ['text'],
+  methods: {
+    input: function() {
+      this.$emit('increment')
+      this.$emit('decrement')
+    }
+  }
+}`,
+  `export default {
+  emits: ["increment", "decrement"],
+  props: ['text'],
+  methods: {
+    input: function() {
+      this.$emit('increment')
+      this.$emit('decrement')
+    }
+  }
+}`,
+  'add emit declaration(has emits property but empty)'
+)
+
+defineInlineTest(
+  transform,
+  {},
+  `export default {
+  emits: ['increment'],
+  props: ['text'],
+  methods: {
+    input: function() {
+      this.$emit('increment')
+      this.$emit('decrement')
+    }
+  }
+}
+`,
+  `export default {
+  emits: ['increment', "decrement"],
+  props: ['text'],
+  methods: {
+    input: function() {
+      this.$emit('increment')
+      this.$emit('decrement')
+    }
+  }
+}`,
+  'add emit declaration(has emits property and not empty)'
+)

transformations/add-emit-declaration.ts

@@ -0,0 +1,48 @@
+import wrap from '../src/wrapAstTransformation'
+import type { ASTTransformation } from '../src/wrapAstTransformation'
+
+export const transformAST: ASTTransformation = ({ root, j }) => {
+//  find the export default
+  const defaultExportBody = root.find(j.ExportDefaultDeclaration)
+
+//  find the CallExpression
+  const emitCalls = defaultExportBody.find(j.CallExpression, node => {
+    return node.callee.object?.type === 'ThisExpression'
+      && node.callee.property?.name === '$emit'
+  })
+
+  if (emitCalls.length) {
+    //  find the $emit argument
+    const eventNames: string[] = []
+    emitCalls.forEach(({ node }) => {
+      if (node.arguments[0]?.type === 'StringLiteral') {
+        eventNames.push(node.arguments[0].value)
+      }
+    })
+
+    //  find the emit property
+    const emitsProperty = defaultExportBody.find(j.ObjectProperty, node => {
+      return node.key.name === 'emits'
+        && node.value.type === 'ArrayExpression'
+    })
+
+    const elements = emitsProperty.length ? emitsProperty.get(0).node.value.elements : []
+    const emits = elements.map((r: { value: string }) => r.value)
+    const hasEmitsProperty = emitsProperty.length
+
+    // push not declare event name into emits
+    eventNames.forEach(r => {
+      if (!emits.includes(r)) {
+        elements.push(j.stringLiteral(r))
+      }
+    })
+
+    if(!hasEmitsProperty){
+    //  no emits property then create emits:[...]  AST
+      defaultExportBody.get(0).node.declaration.properties.unshift(j.objectProperty(j.identifier('emits'),j.arrayExpression(elements)));
+    }
+  }
+}
+
+export default wrap(transformAST)
+export const parser = 'babylon'

transformations/index.ts

@@ -17,6 +17,7 @@ const transformationMap: {
   'scoped-slots-to-slots': require('./scoped-slots-to-slots'),
   'new-directive-api': require('./new-directive-api'),
   'remove-vue-set-and-delete': require('./remove-vue-set-and-delete'),
+  'add-emit-declaration': require('./add-emit-declaration'),
 
   // atomic ones
   'remove-contextual-h-from-render': require('./remove-contextual-h-from-render'),