assert: make myers_diff function more performant

PR-URL: #56303 Refs: #54862 Reviewed-By: Antoine du Hamel <[email protected]> Reviewed-By: Xuguang Mei <[email protected]> Reviewed-By: Ruben Bridgewater <[email protected]> Reviewed-By: Pietro Marchini <[email protected]> Reviewed-By: James M Snell <[email protected]>

Author: Giovanni Bucci

lib/internal/assert/myers_diff.js

@@ -1,10 +1,9 @@
 'use strict';
 
 const{
- Array,
- ArrayPrototypeFill,
  ArrayPrototypePush,
  ArrayPrototypeSlice,
+ Int32Array,
  StringPrototypeEndsWith,
 }=primordials;
 
@@ -26,7 +25,7 @@ function myersDiff(actual, expected, checkCommaDisparity = false){
 constactualLength=actual.length;
 constexpectedLength=expected.length;
 constmax=actualLength+expectedLength;
-constv=ArrayPrototypeFill(Array(2*max+1),0);
+constv=newInt32Array(2*max+1);
 
 consttrace=[];
 
@@ -35,22 +34,24 @@ function myersDiff(actual, expected, checkCommaDisparity = false){
 ArrayPrototypePush(trace,newTrace);
 
 for(letdiagonalIndex=-diffLevel;diagonalIndex<=diffLevel;diagonalIndex+=2){
-letx;
-if(diagonalIndex===-diffLevel||
-(diagonalIndex!==diffLevel&&v[diagonalIndex-1+max]<v[diagonalIndex+1+max])){
-x=v[diagonalIndex+1+max];
-}else{
-x=v[diagonalIndex-1+max]+1;
-}
-
+constoffset=diagonalIndex+max;
+constpreviousOffset=v[offset-1];
+constnextOffset=v[offset+1];
+letx=diagonalIndex===-diffLevel||(diagonalIndex!==diffLevel&&previousOffset<nextOffset) ?
+nextOffset :
+previousOffset+1;
 lety=x-diagonalIndex;
 
-while(x<actualLength&&y<expectedLength&&areLinesEqual(actual[x],expected[y],checkCommaDisparity)){
+while(
+x<actualLength&&
+y<expectedLength&&
+areLinesEqual(actual[x],expected[y],checkCommaDisparity)
+){
 x++;
 y++;
 }
 
-v[diagonalIndex+max]=x;
+v[offset]=x;
 
 if(x>=actualLength&&y>=expectedLength){
 returnbacktrack(trace,actual,expected,checkCommaDisparity);
@@ -71,10 +72,13 @@ function backtrack(trace, actual, expected, checkCommaDisparity){
 for(letdiffLevel=trace.length-1;diffLevel>=0;diffLevel--){
 constv=trace[diffLevel];
 constdiagonalIndex=x-y;
-letprevDiagonalIndex;
+constoffset=diagonalIndex+max;
 
-if(diagonalIndex===-diffLevel||
-(diagonalIndex!==diffLevel&&v[diagonalIndex-1+max]<v[diagonalIndex+1+max])){
+letprevDiagonalIndex;
+if(
+diagonalIndex===-diffLevel||
+(diagonalIndex!==diffLevel&&v[offset-1]<v[offset+1])
+){
 prevDiagonalIndex=diagonalIndex+1;
 }else{
 prevDiagonalIndex=diagonalIndex-1;
@@ -84,8 +88,11 @@ function backtrack(trace, actual, expected, checkCommaDisparity){
 constprevY=prevX-prevDiagonalIndex;
 
 while(x>prevX&&y>prevY){
-constvalue=!checkCommaDisparity||
-StringPrototypeEndsWith(actual[x-1],',') ? actual[x-1] : expected[y-1];
+constactualItem=actual[x-1];
+constvalue=
+!checkCommaDisparity||StringPrototypeEndsWith(actualItem,',') ?
+actualItem :
+expected[y-1];
 ArrayPrototypePush(result,{__proto__: null,type: 'nop', value });
 x--;
 y--;
@@ -110,13 +117,15 @@ function printSimpleMyersDiff(diff){
 
 for(letdiffIdx=diff.length-1;diffIdx>=0;diffIdx--){
 const{ type, value }=diff[diffIdx];
+letcolor=colors.white;
+
 if(type==='insert'){
-message+=`${colors.green}${value}${colors.white}`;
+color=colors.green;
 }elseif(type==='delete'){
-message+=`${colors.red}${value}${colors.white}`;
-}else{
-message+=`${colors.white}${value}${colors.white}`;
+color=colors.red;
 }
+
+message+=`${color}${value}${colors.white}`;
 }
 
 return`\n${message}`;
@@ -129,17 +138,16 @@ function printMyersDiff(diff, operator){
 
 for(letdiffIdx=diff.length-1;diffIdx>=0;diffIdx--){
 const{ type, value }=diff[diffIdx];
-constpreviousType=(diffIdx<(diff.length-1)) ? diff[diffIdx+1].type : null;
-consttypeChanged=previousType&&(type!==previousType);
+constpreviousType=diffIdx<diff.length-1 ? diff[diffIdx+1].type : null;
 
-if(typeChanged&&previousType==='nop'){
-// Avoid grouping if only one line would have been grouped otherwise
+// Avoid grouping if only one line would have been grouped otherwise
+if(previousType==='nop'&&type!==previousType){
 if(nopCount===kNopLinesToCollapse+1){
 message+=`${colors.white}${diff[diffIdx+1].value}\n`;
 }elseif(nopCount===kNopLinesToCollapse+2){
 message+=`${colors.white}${diff[diffIdx+2].value}\n`;
 message+=`${colors.white}${diff[diffIdx+1].value}\n`;
-}if(nopCount>=(kNopLinesToCollapse+3)){
+}elseif(nopCount>=kNopLinesToCollapse+3){
 message+=`${colors.blue}...${colors.white}\n`;
 message+=`${colors.white}${diff[diffIdx+1].value}\n`;
 skipped=true;