Merge pull request #23408 from Microsoft/autoPretty

--pretty-er output by default

src/compiler/sys.ts

@@ -428,6 +428,7 @@ namespace ts {
         newLine: string;
         useCaseSensitiveFileNames: boolean;
         write(s: string): void;
+        writeOutputIsTTY?(): boolean;
         readFile(path: string, encoding?: string): string | undefined;
         getFileSize?(path: string): number;
         writeFile(path: string, data: string, writeByteOrderMark?: boolean): void;
@@ -561,6 +562,9 @@ namespace ts {
                 write(s: string): void {
                     process.stdout.write(s);
                 },
+                writeOutputIsTTY() {
+                    return process.stdout.isTTY;
+                },
                 readFile,
                 writeFile,
                 watchFile: getWatchFile(),

src/compiler/tsc.ts

@@ -19,11 +19,18 @@ namespace ts {
 
     let reportDiagnostic = createDiagnosticReporter(sys);
     function updateReportDiagnostic(options: CompilerOptions) {
-        if (options.pretty) {
+        if (shouldBePretty(options)) {
             reportDiagnostic = createDiagnosticReporter(sys, /*pretty*/ true);
         }
     }
 
+    function shouldBePretty(options: CompilerOptions) {
+        if (typeof options.pretty === "undefined") {
+            return !!sys.writeOutputIsTTY && sys.writeOutputIsTTY();
+        }
+        return options.pretty;
+    }
+
     function padLeft(s: string, length: number) {
         while (s.length < length) {
             s = " " + s;
@@ -159,7 +166,7 @@ namespace ts {
     }
 
     function createWatchStatusReporter(options: CompilerOptions) {
-        return ts.createWatchStatusReporter(sys, !!options.pretty);
+        return ts.createWatchStatusReporter(sys, shouldBePretty(options));
     }
 
     function createWatchOfConfigFile(configParseResult: ParsedCommandLine, optionsToExtend: CompilerOptions) {

src/compiler/types.ts

@@ -4195,7 +4195,7 @@ namespace ts {
         preserveSymlinks?: boolean;
         /* @internal */ preserveWatchOutput?: boolean;
         project?: string;
-        /* @internal */ pretty?: DiagnosticStyle;
+        /* @internal */ pretty?: boolean;
         reactNamespace?: string;
         jsxFactory?: string;
         removeComments?: boolean;
@@ -4293,12 +4293,6 @@ namespace ts {
         JSX,
     }
 
-    /* @internal */
-    export const enum DiagnosticStyle {
-        Simple,
-        Pretty,
-    }
-
     /** Either a parsed command line or a parsed tsconfig.json */
     export interface ParsedCommandLine {
         options: CompilerOptions;

tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -2889,6 +2889,7 @@ declare namespace ts {
         newLine: string;
         useCaseSensitiveFileNames: boolean;
         write(s: string): void;
+        writeOutputIsTTY?(): boolean;
         readFile(path: string, encoding?: string): string | undefined;
         getFileSize?(path: string): number;
         writeFile(path: string, data: string, writeByteOrderMark?: boolean): void;

tests/baselines/reference/api/typescript.d.ts

@@ -2889,6 +2889,7 @@ declare namespace ts {
         newLine: string;
         useCaseSensitiveFileNames: boolean;
         write(s: string): void;
+        writeOutputIsTTY?(): boolean;
         readFile(path: string, encoding?: string): string | undefined;
         getFileSize?(path: string): number;
         writeFile(path: string, data: string, writeByteOrderMark?: boolean): void;