Connect prototype members across files

Amp-Thread-ID: https://ampcode.com/threads/T-01a029e2-5095-710a-9cce-0c6d8645c173

Author: eseliger

snapshots/input/prototype-members/package.json

@@ -0,0 +1,6 @@
+{
+  "name": "prototype-members",
+  "version": "1.0.0",
+  "private": true,
+  "type": "module"
+}

snapshots/input/prototype-members/src/connection.mjs

@@ -0,0 +1,7 @@
+export function Connection() {}
+
+Connection.prototype = {
+  getSchemaVersion() {
+    return 0
+  },
+}

snapshots/input/prototype-members/src/use.mjs

@@ -0,0 +1,6 @@
+/** @import { Connection } from './connection.mjs' */
+
+/** @param {Connection} connection */
+export function schemaVersion(connection) {
+  return connection.getSchemaVersion()
+}

snapshots/input/prototype-members/tsconfig.json

@@ -0,0 +1,11 @@
+{
+  "compilerOptions": {
+    "allowJs": true,
+    "checkJs": true,
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
+    "noEmit": true,
+    "target": "ES2022"
+  },
+  "include": ["src/**/*.mjs"]
+}

snapshots/output/prototype-members/src/connection.mjs

@@ -0,0 +1,16 @@
+// language JavaScript
+// < definition prototype-members 1.0.0 src/`connection.mjs`/
+
+export function Connection() {}
+//              ^^^^^^^^^^ definition prototype-members 1.0.0 src/`connection.mjs`/Connection().
+
+Connection.prototype = {
+//^^^^^^^^^ reference prototype-members 1.0.0 src/`connection.mjs`/Connection().
+//^^^^^^^^^ reference local 3
+//         ^^^^^^^^^ reference local 2
+  getSchemaVersion() {
+//^^^^^^^^^^^^^^^^ definition prototype-members 1.0.0 src/`connection.mjs`/Connection().getSchemaVersion().
+    return 0
+  },
+}
+

snapshots/output/prototype-members/src/use.mjs

@@ -0,0 +1,14 @@
+// language JavaScript
+// < definition prototype-members 1.0.0 src/`use.mjs`/
+
+/** @import { Connection } from './connection.mjs' */
+
+/** @param {Connection} connection */
+export function schemaVersion(connection) {
+//              ^^^^^^^^^^^^^ definition prototype-members 1.0.0 src/`use.mjs`/schemaVersion().
+//                            ^^^^^^^^^^ definition prototype-members 1.0.0 src/`use.mjs`/schemaVersion().(connection)
+  return connection.getSchemaVersion()
+//       ^^^^^^^^^^ reference prototype-members 1.0.0 src/`use.mjs`/schemaVersion().(connection)
+//                  ^^^^^^^^^^^^^^^^ reference prototype-members 1.0.0 src/`connection.mjs`/Connection().getSchemaVersion().
+}
+

src/FileIndexer.ts

@@ -424,6 +424,28 @@ export class FileIndexer {
     }
     return relationships
   }
+
+  private prototypeAssignmentOwner(node: ts.Node): ts.Declaration | undefined {
+    if (!ts.isObjectLiteralExpression(node)) {
+      return
+    }
+    const assignment = node.parent
+    if (
+      !ts.isBinaryExpression(assignment) ||
+      assignment.operatorToken.kind !== ts.SyntaxKind.EqualsToken ||
+      assignment.right !== node ||
+      !ts.isPropertyAccessExpression(assignment.left) ||
+      assignment.left.name.text !== 'prototype'
+    ) {
+      return
+    }
+    let symbol = this.checker.getSymbolAtLocation(assignment.left.expression)
+    if (symbol && (symbol.flags & ts.SymbolFlags.Alias) !== 0) {
+      symbol = this.checker.getAliasedSymbol(symbol)
+    }
+    return symbol?.valueDeclaration ?? symbol?.declarations?.[0]
+  }
+
   private scipSymbol(node: ts.Node): ScipSymbol {
     const fromCache: ScipSymbol | undefined =
       this.globalSymbolTable.get(node) || this.localSymbolTable.get(node)
@@ -490,6 +512,14 @@ export class FileIndexer {
       }
     }
 
+    const prototypeOwner = this.prototypeAssignmentOwner(node)
+    if (prototypeOwner) {
+      // Methods in `Constructor.prototype = { ... }` belong to the constructor,
+      // not to an anonymous object local to this file. Giving that object the
+      // constructor's identity makes its members stable across files.
+      return this.cached(node, this.scipSymbol(prototypeOwner))
+    }
+
     const owner = this.scipSymbol(node.parent)
     if (owner.isEmpty() || owner.isLocal()) {
       return this.newLocalSymbol(node)