[TypeScript Plugin] Moved the diagnostics' positions to the prop's type instead of the value for client-boundary warnings (vercel#79193)

Best be reviewed with "Hide whitespace".

### Why?

Since it was matching `ts.isObjectBindingPattern`, which checks only the
destructured props:

![CleanShot 2025-05-14 at 12 17
25@2x](https://github.com/user-attachments/assets/44aaffd2-9276-486e-86ce-acb77d488ab0)

It didn't handle non-destructured:

![CleanShot 2025-05-14 at 12 17
34@2x](https://github.com/user-attachments/assets/23abc130-3e17-4f72-89a2-bc084841f52f)

Therefore, I think it's more natural to target the types, not the props
value, as the cause of this warning is actually the types:

![CleanShot 2025-05-14 at 12 18
00@2x](https://github.com/user-attachments/assets/0a5a64c8-1ac9-4b0f-8fe7-20e78db2acec)

![CleanShot 2025-05-14 at 12 17
53@2x](https://github.com/user-attachments/assets/72008c25-7d7b-46e4-8e2f-e52f01e50b80)

x-ref:
vercel#79144 (comment)

---------

Co-authored-by: Janka Uryga <lolzatu2@gmail.com>

Author: devjiwonchoi

.changeset/shy-impalas-add.md

@@ -0,0 +1,5 @@
+---
+"next": patch
+---
+
+[TypeScript Plugin] Moved the diagnostics' positions to the prop's type instead of the value for client-boundary warnings.

packages/next/src/server/typescript/rules/client-boundary.ts

@@ -43,57 +43,69 @@ const clientBoundary = {
     const isErrorFile = /[\\/]error\.tsx?$/.test(source.fileName)
     const isGlobalErrorFile = /[\\/]global-error\.tsx?$/.test(source.fileName)
 
-    const props = node.parameters?.[0]?.name
-    if (props && ts.isObjectBindingPattern(props)) {
-      for (const prop of (props as tsModule.ObjectBindingPattern).elements) {
-        const type = typeChecker.getTypeAtLocation(prop)
-        const typeDeclarationNode = type.symbol?.getDeclarations()?.[0]
-        const propName = (prop.propertyName || prop.name).getText()
-
-        if (typeDeclarationNode) {
-          if (ts.isFunctionTypeNode(typeDeclarationNode)) {
-            // By convention, props named "action" can accept functions since we
-            // assume these are Server Actions. Structurally, there's no
-            // difference between a Server Action and a normal function until
-            // TypeScript exposes directives in the type of a function. This
-            // will miss accidentally passing normal functions but a false
-            // negative is better than a false positive given how frequent the
-            // false-positive would be.
-            const maybeServerAction =
-              propName === 'action' || /.+Action$/.test(propName)
-
-            // There's a special case for the error file that the `reset` prop
-            // is allowed to be a function:
-            // https://github.com/vercel/next.js/issues/46573
-            const isErrorReset =
-              (isErrorFile || isGlobalErrorFile) && propName === 'reset'
-
-            if (!maybeServerAction && !isErrorReset) {
-              diagnostics.push({
-                file: source,
-                category: ts.DiagnosticCategory.Warning,
-                code: NEXT_TS_ERRORS.INVALID_CLIENT_ENTRY_PROP,
-                messageText:
-                  `Props must be serializable for components in the "use client" entry file. ` +
-                  `"${propName}" is a function that's not a Server Action. ` +
-                  `Rename "${propName}" either to "action" or have its name end with "Action" e.g. "${propName}Action" to indicate it is a Server Action.`,
-                start: prop.getStart(),
-                length: prop.getWidth(),
-              })
+    const props = node.parameters?.[0]
+    if (props) {
+      const propsType = typeChecker.getTypeAtLocation(props)
+      const typeNode = propsType.symbol?.getDeclarations()?.[0]
+
+      if (typeNode && ts.isTypeLiteralNode(typeNode)) {
+        for (const member of typeNode.members) {
+          if (ts.isPropertySignature(member)) {
+            const propName = member.name.getText()
+            const propType = member.type
+
+            if (propType) {
+              const propTypeInfo = typeChecker.getTypeAtLocation(propType)
+              const typeDeclarationNode =
+                propTypeInfo.symbol?.getDeclarations()?.[0]
+
+              if (typeDeclarationNode) {
+                if (ts.isFunctionTypeNode(typeDeclarationNode)) {
+                  // By convention, props named "action" can accept functions since we
+                  // assume these are Server Actions. Structurally, there's no
+                  // difference between a Server Action and a normal function until
+                  // TypeScript exposes directives in the type of a function. This
+                  // will miss accidentally passing normal functions but a false
+                  // negative is better than a false positive given how frequent the
+                  // false-positive would be.
+                  const maybeServerAction =
+                    propName === 'action' || /.+Action$/.test(propName)
+
+                  // There's a special case for the error file that the `reset` prop
+                  // is allowed to be a function:
+                  // https://github.com/vercel/next.js/issues/46573
+                  const isErrorReset =
+                    (isErrorFile || isGlobalErrorFile) && propName === 'reset'
+
+                  if (!maybeServerAction && !isErrorReset) {
+                    diagnostics.push({
+                      file: source,
+                      category: ts.DiagnosticCategory.Warning,
+                      code: NEXT_TS_ERRORS.INVALID_CLIENT_ENTRY_PROP,
+                      messageText:
+                        `Props must be serializable for components in the "use client" entry file. ` +
+                        `"${propName}" is a function that's not a Server Action. ` +
+                        `Rename "${propName}" either to "action" or have its name end with "Action" e.g. "${propName}Action" to indicate it is a Server Action.`,
+                      start: propType.getStart(),
+                      length: propType.getWidth(),
+                    })
+                  }
+                } else if (
+                  // Show warning for not serializable props.
+                  ts.isConstructorTypeNode(typeDeclarationNode) ||
+                  ts.isClassDeclaration(typeDeclarationNode)
+                ) {
+                  diagnostics.push({
+                    file: source,
+                    category: ts.DiagnosticCategory.Warning,
+                    code: NEXT_TS_ERRORS.INVALID_CLIENT_ENTRY_PROP,
+                    messageText: `Props must be serializable for components in the "use client" entry file, "${propName}" is invalid.`,
+                    start: propType.getStart(),
+                    length: propType.getWidth(),
+                  })
+                }
+              }
             }
-          } else if (
-            // Show warning for not serializable props.
-            ts.isConstructorTypeNode(typeDeclarationNode) ||
-            ts.isClassDeclaration(typeDeclarationNode)
-          ) {
-            diagnostics.push({
-              file: source,
-              category: ts.DiagnosticCategory.Warning,
-              code: NEXT_TS_ERRORS.INVALID_CLIENT_ENTRY_PROP,
-              messageText: `Props must be serializable for components in the "use client" entry file, "${propName}" is invalid.`,
-              start: prop.getStart(),
-              length: prop.getWidth(),
-            })
           }
         }
       }

test/development/typescript-plugin/client-boundary/app/non-serializable-action-props.tsx

@@ -4,13 +4,7 @@ class Class {}
 
 type ArrowFunctionTypeAlias = () => void
 
-export default function ClientComponent({
-  _arrowFunctionAction,
-  _arrowFunctionTypeAliasAction,
-  // Doesn't make sense, but check for loophole
-  _classAction,
-  _constructorAction,
-}: {
+export default function ClientComponent(props: {
   _arrowFunctionAction: () => void
   _arrowFunctionTypeAliasAction: ArrowFunctionTypeAlias
   // Doesn't make sense, but check for loophole

test/development/typescript-plugin/client-boundary/app/non-serializable-props.tsx

@@ -4,12 +4,7 @@ class Class {}
 
 type ArrowFunctionTypeAlias = () => void
 
-export default function ClientComponent({
-  _arrowFunction,
-  _arrowFunctionTypeAlias,
-  _class,
-  _constructor,
-}: {
+export default function ClientComponent(props: {
   _arrowFunction: () => void
   _arrowFunctionTypeAlias: ArrowFunctionTypeAlias
   _class: Class

test/development/typescript-plugin/client-boundary/app/serializable-props.tsx

@@ -1,14 +1,6 @@
 'use client'
 
-export default function ClientComponent({
-  _string,
-  _number,
-  _boolean,
-  _array,
-  _object,
-  _null,
-  _undefined,
-}: {
+export default function ClientComponent(props: {
   _string: string
   _number: number
   _boolean: boolean

test/development/typescript-plugin/client-boundary/client-boundary.test.ts

@@ -58,15 +58,15 @@ describe('typescript-plugin - client-boundary', () => {
        "app/non-serializable-action-props.tsx": [
          {
            "code": 71007,
-           "length": 12,
+           "length": 5,
            "messageText": "Props must be serializable for components in the "use client" entry file, "_classAction" is invalid.",
-           "start": 221,
+           "start": 276,
          },
          {
            "code": 71007,
-           "length": 18,
+           "length": 14,
            "messageText": "Props must be serializable for components in the "use client" entry file, "_constructorAction" is invalid.",
-           "start": 237,
+           "start": 304,
          },
        ],
      }
@@ -91,27 +91,27 @@ describe('typescript-plugin - client-boundary', () => {
        "app/non-serializable-props.tsx": [
          {
            "code": 71007,
-           "length": 14,
+           "length": 10,
            "messageText": "Props must be serializable for components in the "use client" entry file. "_arrowFunction" is a function that's not a Server Action. Rename "_arrowFunction" either to "action" or have its name end with "Action" e.g. "_arrowFunctionAction" to indicate it is a Server Action.",
-           "start": 116,
+           "start": 139,
          },
          {
            "code": 71007,
-           "length": 23,
+           "length": 22,
            "messageText": "Props must be serializable for components in the "use client" entry file. "_arrowFunctionTypeAlias" is a function that's not a Server Action. Rename "_arrowFunctionTypeAlias" either to "action" or have its name end with "Action" e.g. "_arrowFunctionTypeAliasAction" to indicate it is a Server Action.",
-           "start": 134,
+           "start": 177,
          },
          {
            "code": 71007,
-           "length": 6,
+           "length": 5,
            "messageText": "Props must be serializable for components in the "use client" entry file, "_class" is invalid.",
-           "start": 161,
+           "start": 210,
          },
          {
            "code": 71007,
-           "length": 12,
+           "length": 14,
            "messageText": "Props must be serializable for components in the "use client" entry file, "_constructor" is invalid.",
-           "start": 171,
+           "start": 232,
          },
        ],
      }