Add option to show warnings when props could be accessed via this

lib/rules/no-unused-properties.js

@@ -55,6 +55,9 @@ const GROUP_SETUP = 'setup'
 const GROUP_WATCHER = 'watch'
 const GROUP_EXPOSE = 'expose'
 
+const STOPREPORTING_UNKNOWN = 'unknownPropertyAccess'
+const STOPREPORTING_RETURN = 'returnInstance'
+
 const PROPERTY_LABEL = {
   props: 'property',
   data: 'data',
@@ -206,7 +209,15 @@ module.exports = {
             uniqueItems: true
           },
           deepData: { type: 'boolean' },
-          ignorePublicMembers: { type: 'boolean' }
+          ignorePublicMembers: { type: 'boolean' },
+          stopReporting: {
+            type: 'array',
+            items: {
+              enum: [STOPREPORTING_UNKNOWN, STOPREPORTING_RETURN]
+            },
+            additionalItems: false,
+            uniqueItems: true
+          }
         },
         additionalProperties: false
       }
@@ -221,8 +232,21 @@ module.exports = {
     const groups = new Set(options.groups || [GROUP_PROPERTY])
     const deepData = Boolean(options.deepData)
     const ignorePublicMembers = Boolean(options.ignorePublicMembers)
+    const stopReporting = new Set(
+      options.stopReporting || [STOPREPORTING_UNKNOWN, STOPREPORTING_RETURN]
+    )
+    const stopReportingUnknown = Boolean(
+      stopReporting.has(STOPREPORTING_UNKNOWN)
+    )
+    const stopReportingReturn = Boolean(stopReporting.has(STOPREPORTING_RETURN))
 
-    const propertyReferenceExtractor = definePropertyReferenceExtractor(context)
+    const propertyReferenceExtractor = definePropertyReferenceExtractor(
+      context,
+      {
+        stopReportingUnknown,
+        stopReportingReturn
+      }
+    )
 
     /** @type {TemplatePropertiesContainer} */
     const templatePropertiesContainer = {

lib/utils/property-references.js

@@ -92,7 +92,10 @@ module.exports = {
 /**
  * @param {RuleContext} context The rule context.
  */
-function definePropertyReferenceExtractor(context) {
+function definePropertyReferenceExtractor(
+  context,
+  { stopReportingUnknown = true, stopReportingReturn = true } = {}
+) {
   /** @type {Map<Expression, IPropertyReferences>} */
   const cacheForExpression = new Map()
   /** @type {Map<Pattern, IPropertyReferences>} */
@@ -314,9 +317,15 @@ function definePropertyReferenceExtractor(context) {
           if (parent.object === node) {
             // `arg.foo`
             const name = utils.getStaticPropertyName(parent)
-            return name
-              ? new PropertyReferencesForMember(parent, name, withInTemplate)
-              : ANY
+            if (name) {
+              return new PropertyReferencesForMember(
+                parent,
+                name,
+                withInTemplate
+              )
+            } else {
+              return stopReportingUnknown ? ANY : NEVER
+            }
           }
           return NEVER
         }
@@ -331,12 +340,18 @@ function definePropertyReferenceExtractor(context) {
           return extractFromExpression(parent, withInTemplate)
         }
         case 'ArrowFunctionExpression':
-        case 'ReturnStatement':
         case 'VExpressionContainer':
         case 'Property':
         case 'ArrayExpression': {
           return maybeExternalUsed(parent) ? ANY : NEVER
         }
+        case 'ReturnStatement': {
+          if (stopReportingReturn) {
+            return maybeExternalUsed(parent) ? ANY : NEVER
+          } else {
+            return NEVER
+          }
+        }
       }
       return NEVER
     }

tests/lib/rules/no-unused-properties.js

@@ -21,6 +21,30 @@ const allOptions = [
 ]
 const deepDataOptions = [{ groups: ['data'], deepData: true }]
 
+const stopReportingOptions = {
+  // Stop reporting errors when accessing via unknown property, e.g. this[varName]
+  unknownPropertyAccess: [
+    {
+      groups: ['computed'],
+      stopReporting: ['unknownPropertyAccess']
+    }
+  ],
+  // Stop reporting errors when returning this
+  returnInstance: [
+    {
+      groups: ['computed'],
+      stopReporting: ['returnInstance']
+    }
+  ],
+  // Don't stop reporting any errors
+  none: [
+    {
+      groups: ['computed'],
+      stopReporting: []
+    }
+  ]
+}
+
 tester.run('no-unused-properties', rule, {
   valid: [
     // a property used in a script expression
@@ -1697,9 +1721,58 @@ tester.run('no-unused-properties', rule, {
         },
       };
       </script>`
+    },
+
+    // stopReportingOptions: unknownPropertyAccess
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+        export default {
+          computed: {
+            one () {
+              return 1
+            },
+            two () {
+              return 2
+            },
+          },
+          methods: {
+            handler () {
+              const i = 'two'
+              const b = this[i]
+            },
+          }
+        }
+      </script>
+      `,
+      options: stopReportingOptions.unknownPropertyAccess
+    },
+    // stopReportingOptions: returnInstance
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+        export default {
+          computed: {
+            one () {
+              return 1
+            },
+            two () {
+              return 2
+            },
+          },
+          methods: {
+            handler () {
+              return this
+            },
+          }
+        }
+      </script>
+      `,
+      options: stopReportingOptions.returnInstance
     }
   ],
-
   invalid: [
     // unused property
     {
@@ -2803,6 +2876,139 @@ tester.run('no-unused-properties', rule, {
           line: 10
         }
       ]
+    },
+
+    // stopReportingOptions: unknownPropertyAccess
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+        export default {
+          computed: {
+            one () {
+              return 1
+            },
+            two () {
+              return 2
+            }
+          },
+          methods: {
+            handler () {
+              const a = this.one
+              return this
+            },
+          }
+        }
+      </script>
+      `,
+      options: stopReportingOptions.unknownPropertyAccess,
+      errors: [
+        {
+          message: "'two' of computed property found, but never used.",
+          line: 8
+        }
+      ]
+    },
+    // stopReportingOptions: returnInstance
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+        export default {
+          computed: {
+            one () {
+              return 1
+            },
+            two () {
+              return 2
+            }
+          },
+          methods: {
+            handler () {
+              const a = this.one
+              const i = 'two'
+              return this[i]
+            },
+          }
+        }
+      </script>
+      `,
+      options: stopReportingOptions.returnInstance,
+      errors: [
+        {
+          message: "'two' of computed property found, but never used.",
+          line: 8
+        }
+      ]
+    },
+    // stopReportingOptions: []
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+        export default {
+          computed: {
+            one () {
+              return 1
+            },
+            two () {
+              return 2
+            }
+          },
+          methods: {
+            handler () {
+              const a = this.one
+              const i = 'two'
+              const b = this[i]
+              return this
+            },
+          }
+        }
+      </script>
+      `,
+      options: stopReportingOptions.none,
+      errors: [
+        {
+          message: "'two' of computed property found, but never used.",
+          line: 8
+        }
+      ]
+    },
+    {
+      filename: 'test.vue',
+      code: `
+      <script>
+        export default {
+          data () {
+            return {
+              foo: {
+                bar: 1
+              },
+              baz: 2
+            }
+          },
+          methods: {
+            handler () {
+              console.log(this.baz)
+              return this.foo
+            },
+          }
+        }
+      </script>
+      `,
+      options: [
+        {
+          groups: ['data'],
+          deepData: true,
+          stopReporting: []
+        }
+      ],
+      errors: [
+        {
+          message: "'foo.bar' of data found, but never used.",
+          line: 7
+        }
+      ]
     }
   ]
 })