Function expandMissingPropertiesMessage

typescript/src/ts/validate.ts:82–106

* For TypeScript error 2740 (missing required properties, truncated with "and N more"), * uses the type checker to compute the full list of missing required properties from the * variable declaration at `position` in `file`. Returns `undefined` if the declaration * cannot be located o

(checker: ts.TypeChecker, file: ts.SourceFile, position: number)

     * cannot be located or yields no missing properties (fallback to the original message).
     */
    function expandMissingPropertiesMessage(checker: ts.TypeChecker, file: ts.SourceFile, position: number): string | undefined {
        for (const stmt of file.statements) {
            if (ts.isVariableStatement(stmt)) {
                for (const decl of stmt.declarationList.declarations) {
                    // Match the specific declaration that spans the diagnostic position.
                    // Use getStart() to exclude leading trivia from the range check.
                    if (decl.getStart(file) <= position && position <= decl.end &&
                            decl.type && ts.isTypeReferenceNode(decl.type) && decl.initializer) {
                        const targetType = checker.getTypeAtLocation(decl.type);
                        const sourceType = checker.getTypeAtLocation(decl.initializer);
                        const sourceProps = new Set(sourceType.getProperties().map(p => p.name));
                        const missingProps = targetType.getProperties()
                            .filter(p => !(p.flags & ts.SymbolFlags.Optional) && !sourceProps.has(p.name))
                            .map(p => p.name);
                        if (missingProps.length > 0) {
                            const srcStr = checker.typeToString(sourceType, undefined, ts.TypeFormatFlags.NoTruncation);
                            const tgtStr = checker.typeToString(targetType, undefined, ts.TypeFormatFlags.NoTruncation);
                            return `Type '${srcStr}' is missing the following properties from type '${tgtStr}': ${missingProps.join(", ")}`;
                        }
                    }
                }
            }
        }
        return undefined;
    }

    function createModuleTextFromJson(jsonObject: object) {
        return success(`import { ${typeName} } from './schema';\nconst json: ${typeName} = ${JSON.stringify(jsonObject, undefined, 2)};\n`);