Introduce truncation into node builder and symbol display part writer

src/compiler/transformers/declarations.ts

@@ -11,11 +11,12 @@ namespace ts {
 
     const declarationEmitNodeBuilderFlags =
         NodeBuilderFlags.MultilineObjectLiterals |
-        TypeFormatFlags.WriteClassExpressionAsTypeLiteral |
+        NodeBuilderFlags.WriteClassExpressionAsTypeLiteral |
         NodeBuilderFlags.UseTypeOfFunction |
         NodeBuilderFlags.UseStructuralFallback |
         NodeBuilderFlags.AllowEmptyTuple |
-        NodeBuilderFlags.GenerateNamesForShadowedTypeParams;
+        NodeBuilderFlags.GenerateNamesForShadowedTypeParams |
+        NodeBuilderFlags.NoTruncation;
 
     /**
      * Transforms a ts file into a .d.ts file

src/compiler/utilities.ts

@@ -21,6 +21,8 @@ namespace ts {
 
     export const externalHelpersModuleNameText = "tslib";
 
+    export const defaultMaximumTruncationLength = 160;
+
     export function getDeclarationOfKind<T extends Declaration>(symbol: Symbol, kind: T["kind"]): T | undefined {
         const declarations = symbol.declarations;
         if (declarations) {

src/services/utilities.ts

@@ -1435,14 +1435,25 @@ namespace ts {
 
     const displayPartWriter = getDisplayPartWriter();
     function getDisplayPartWriter(): DisplayPartsSymbolWriter {
+        const absoluteMaximumLength = defaultMaximumTruncationLength * 10; // A hard cutoff to avoid overloading the messaging channel in worst-case scenarios
         let displayParts: SymbolDisplayPart[];
         let lineStart: boolean;
         let indent: number;
+        let length: number;
 
         resetWriter();
         const unknownWrite = (text: string) => writeKind(text, SymbolDisplayPartKind.text);
         return {
-            displayParts: () => displayParts,
+            displayParts: () => {
+                const finalText = displayParts.length && displayParts[displayParts.length - 1].text;
+                if (length > absoluteMaximumLength && finalText && finalText !== "...") {
+                    if (!isWhiteSpaceLike(finalText.charCodeAt(finalText.length - 1))) {
+                        displayParts.push(displayPart(" ", SymbolDisplayPartKind.space));
+                    }
+                    displayParts.push(displayPart("...", SymbolDisplayPartKind.punctuation));
+                }
+                return displayParts;
+            },
             writeKeyword: text => writeKind(text, SymbolDisplayPartKind.keyword),
             writeOperator: text => writeKind(text, SymbolDisplayPartKind.operator),
             writePunctuation: text => writeKind(text, SymbolDisplayPartKind.punctuation),
@@ -1472,26 +1483,34 @@ namespace ts {
         };
 
         function writeIndent() {
+            if (length > absoluteMaximumLength) return;
             if (lineStart) {
                 const indentString = getIndentString(indent);
                 if (indentString) {
+                    length += indentString.length;
                     displayParts.push(displayPart(indentString, SymbolDisplayPartKind.space));
                 }
                 lineStart = false;
             }
         }
 
         function writeKind(text: string, kind: SymbolDisplayPartKind) {
+            if (length > absoluteMaximumLength) return;
             writeIndent();
+            length += text.length;
             displayParts.push(displayPart(text, kind));
         }
 
         function writeSymbol(text: string, symbol: Symbol) {
+            if (length > absoluteMaximumLength) return;
             writeIndent();
+            length += text.length;
             displayParts.push(symbolPart(text, symbol));
         }
 
         function writeLine() {
+            if (length > absoluteMaximumLength) return;
+            length += 1;
             displayParts.push(lineBreakPart());
             lineStart = true;
         }
@@ -1500,6 +1519,7 @@ namespace ts {
             displayParts = [];
             lineStart = true;
             indent = 0;
+            length = 0;
         }
     }
 

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

@@ -6031,6 +6031,7 @@ declare namespace ts {
     const emptyMap: ReadonlyMap<never>;
     const emptyUnderscoreEscapedMap: ReadonlyUnderscoreEscapedMap<never>;
     const externalHelpersModuleNameText = "tslib";
+    const defaultMaximumTruncationLength = 160;
     function getDeclarationOfKind<T extends Declaration>(symbol: Symbol, kind: T["kind"]): T | undefined;
     /** Create a new escaped identifier map. */
     function createUnderscoreEscapedMap<T>(): UnderscoreEscapedMap<T>;

tests/baselines/reference/errorWithTruncatedType.errors.txt

@@ -1,4 +1,4 @@
-tests/cases/compiler/errorWithTruncatedType.ts(10,5): error TS2322: Type '{ propertyWithAnExceedinglyLongName1: string; propertyWithAnExceedinglyLongName2: string; propert...' is not assignable to type 'string'.
+tests/cases/compiler/errorWithTruncatedType.ts(10,5): error TS2322: Type '{ propertyWithAnExceedinglyLongName1: string; propertyWithAnExceedinglyLongName2: string; propertyWithAnExceedinglyLongName3: string; propertyWithAnExceedinglyLongName4: string; propertyWithAnExceedinglyLongName5: string; }' is not assignable to type 'string'.
 
 
 ==== tests/cases/compiler/errorWithTruncatedType.ts (1 errors) ====
@@ -13,5 +13,5 @@ tests/cases/compiler/errorWithTruncatedType.ts(10,5): error TS2322: Type '{ prop
     // String representation of type of 'x' should be truncated in error message
     var s: string = x;
         ~
-!!! error TS2322: Type '{ propertyWithAnExceedinglyLongName1: string; propertyWithAnExceedinglyLongName2: string; propert...' is not assignable to type 'string'.
+!!! error TS2322: Type '{ propertyWithAnExceedinglyLongName1: string; propertyWithAnExceedinglyLongName2: string; propertyWithAnExceedinglyLongName3: string; propertyWithAnExceedinglyLongName4: string; propertyWithAnExceedinglyLongName5: string; }' is not assignable to type 'string'.