Clean up combineCodeTextAndErrorLines (#2745)

src/test/lines.ts

@@ -72,7 +72,7 @@ export function parseLine(text: string): Line {
  * @param code - If line represents error markup, this is the line of code preceding the markup.
  *               Otherwise, this parameter is not required.
  */
-export function printLine(line: Line, code?: string): string | null {
+export function printLine(line: Line, code?: string): string | undefined {
     if (line instanceof ErrorLine) {
         if (code == null) {
            throw new Error("Must supply argument for code parameter when line is an ErrorLine");
@@ -108,5 +108,5 @@ export function printLine(line: Line, code?: string): string | null {
     } else if (line instanceof CodeLine) {
         return line.contents;
     }
-    return null;
+    return undefined;
 }

src/test/parse.ts

@@ -17,6 +17,7 @@
 import * as ts from "typescript";
 import {format} from "util";
 
+import {flatMap, mapDefined} from "../utils";
 import {
     CodeLine,
     EndErrorLine,
@@ -200,11 +201,7 @@ export function createMarkupFromErrors(code: string, lintErrors: LintError[]) {
 
         if (startPos.line === endPos.line) {
             // single line error
-            errorLinesForCodeText[startPos.line].push(new EndErrorLine(
-                startPos.col,
-                endPos.col,
-                message,
-            ));
+            errorLinesForCodeText[startPos.line].push(new EndErrorLine(startPos.col, endPos.col, message));
         } else {
             // multiline error
             errorLinesForCodeText[startPos.line].push(new MultilineErrorLine(startPos.col));
@@ -215,20 +212,10 @@ export function createMarkupFromErrors(code: string, lintErrors: LintError[]) {
         }
     }
 
-    const finalText = combineCodeTextAndErrorLines(codeText, errorLinesForCodeText);
-    return finalText.join("\n");
+    return flatMap(codeText, (line, i) => [line, ...mapDefined(errorLinesForCodeText[i], (err) => printLine(err, line))]).join("\n");
 }
 /* tslint:enable:object-literal-sort-keys */
 
-function combineCodeTextAndErrorLines(codeText: string[], errorLinesForCodeText: ErrorLine[][]) {
-    return codeText.reduce<string[]>((resultText, code, i) => {
-        resultText.push(code);
-        const errorPrintLines = errorLinesForCodeText[i].map((line) => printLine(line, code)).filter((line) => line !== null) as string[];
-        resultText.push(...errorPrintLines);
-        return resultText;
-    }, []);
-}
-
 function createCodeLineNoToErrorsMap(lines: Line[]) {
     const errorLinesForCodeLine: ErrorLine[][] = [];
     for (const line of lines) {

src/utils.ts

@@ -140,10 +140,10 @@ export function find<T, U>(inputs: T[], getResult: (t: T) => U | undefined): U |
 }
 
 /** Returns an array that is the concatenation of all output arrays. */
-export function flatMap<T, U>(inputs: T[], getOutputs: (input: T) => U[]): U[] {
+export function flatMap<T, U>(inputs: T[], getOutputs: (input: T, index: number) => U[]): U[] {
     const out = [];
-    for (const input of inputs) {
-        out.push(...getOutputs(input));
+    for (let i = 0; i < inputs.length; i++) {
+        out.push(...getOutputs(inputs[i], i));
     }
     return out;
 }