Move tsconfig root checking out of common JSON checking function

Author: andrewbranch

src/compiler/commandLineParser.ts

@@ -1767,11 +1767,35 @@ namespace ts {
         onSetUnknownOptionKeyValueInRoot(key: string, keyNode: PropertyName, value: CompilerOptionsValue, valueNode: Expression): void;
     }
 
+    function convertConfigFileToObject(sourceFile: JsonSourceFile, errors: Push<Diagnostic>, optionsIterator: JsonConversionNotifier): any {
+        const rootExpression: Expression | undefined = sourceFile.statements[0]?.expression;
+        const knownRootOptions = getTsconfigRootOptionsMap();
+        if (rootExpression && rootExpression.kind !== SyntaxKind.ObjectLiteralExpression) {
+            errors.push(createDiagnosticForNodeInSourceFile(
+                sourceFile,
+                rootExpression,
+                Diagnostics.The_root_value_of_a_0_file_must_be_an_object,
+                getBaseFileName(sourceFile.fileName) === "jsconfig.json" ? "jsconfig.json" : "tsconfig.json"
+            ));
+            // Last-ditch error recovery. Somewhat useful because the JSON parser will recover from some parse errors by
+            // synthesizing a top-level array literal expression. There's a reasonable chance the first element of that
+            // array is a well-formed configuration object, made into an array element by stray characters.
+            if (isArrayLiteralExpression(rootExpression)) {
+                const firstObject = find(rootExpression.elements, isObjectLiteralExpression);
+                if (firstObject) {
+                    return convertToObjectWorker(sourceFile, firstObject, errors, /*returnValue*/ true, knownRootOptions, optionsIterator);
+                }
+            }
+            return {};
+        }
+        return convertToObjectWorker(sourceFile, rootExpression, errors, /*returnValue*/ true, knownRootOptions, optionsIterator);
+    }
+
     /**
      * Convert the json syntax tree into the json value
      */
     export function convertToObject(sourceFile: JsonSourceFile, errors: Push<Diagnostic>): any {
-        return convertToObjectWorker(sourceFile, errors, /*returnValue*/ true, /*knownRootOptions*/ undefined, /*jsonConversionNotifier*/ undefined);
+        return convertToObjectWorker(sourceFile, sourceFile.statements[0]?.expression, errors, /*returnValue*/ true, /*knownRootOptions*/ undefined, /*jsonConversionNotifier*/ undefined);
     }
 
     /**
@@ -1782,33 +1806,15 @@ namespace ts {
     /*@internal*/
     export function convertToObjectWorker(
         sourceFile: JsonSourceFile,
+        rootExpression: Expression | undefined,
         errors: Push<Diagnostic>,
         returnValue: boolean,
         knownRootOptions: CommandLineOption | undefined,
         jsonConversionNotifier: JsonConversionNotifier | undefined): any {
-        if (!sourceFile.statements.length) {
+        if (!rootExpression) {
             return returnValue ? {} : undefined;
         }
 
-        const rootExpression: Expression = sourceFile.statements[0].expression;
-        if (rootExpression.kind !== SyntaxKind.ObjectLiteralExpression) {
-            errors.push(createDiagnosticForNodeInSourceFile(
-                sourceFile,
-                rootExpression,
-                Diagnostics.The_root_value_of_a_0_file_must_be_an_object,
-                getBaseFileName(sourceFile.fileName) === "jsconfig.json" ? "jsconfig.json" : "tsconfig.json"
-            ));
-            // Last-ditch error recovery. Somewhat useful because the JSON parser will recover from some parse errors by
-            // synthesizing a top-level array literal expression. There's a reasonable chance the first element of that
-            // array is a well-formed configuration object, made into an array element by stray characters.
-            if (isArrayLiteralExpression(rootExpression)) {
-                const firstObject = find(rootExpression.elements, isObjectLiteralExpression);
-                if (firstObject) {
-                    return convertPropertyValueToJson(firstObject, knownRootOptions);
-                }
-            }
-            return returnValue ? {} : undefined;
-        }
         return convertPropertyValueToJson(rootExpression, knownRootOptions);
 
         function isRootOptionMap(knownOptions: ESMap<string, CommandLineOption> | undefined) {
@@ -2752,7 +2758,7 @@ namespace ts {
                 }
             }
         };
-        const json = convertToObjectWorker(sourceFile, errors, /*returnValue*/ true, getTsconfigRootOptionsMap(), optionsIterator);
+        const json = convertConfigFileToObject(sourceFile, errors, optionsIterator);
 
         if (!typeAcquisition) {
             if (typingOptionstypeAcquisition) {

src/compiler/parser.ts

@@ -819,7 +819,7 @@ namespace ts {
             scriptKind = ensureScriptKind(fileName, scriptKind);
             if (scriptKind === ScriptKind.JSON) {
                 const result = parseJsonText(fileName, sourceText, languageVersion, syntaxCursor, setParentNodes);
-                convertToObjectWorker(result, result.parseDiagnostics, /*returnValue*/ false, /*knownRootOptions*/ undefined, /*jsonConversionNotifier*/ undefined);
+                convertToObjectWorker(result, result.statements[0]?.expression, result.parseDiagnostics, /*returnValue*/ false, /*knownRootOptions*/ undefined, /*jsonConversionNotifier*/ undefined);
                 result.referencedFiles = emptyArray;
                 result.typeReferenceDirectives = emptyArray;
                 result.libReferenceDirectives = emptyArray;