getBlockStringIndentation: simplify implementation (#2748)

Author: IvanGoncharov

src/language/__tests__/blockString-test.js

@@ -96,33 +96,32 @@ describe('dedentBlockStringValue', () => {
 });
 
 describe('getBlockStringIndentation', () => {
-  it('returns zero for an empty array', () => {
-    expect(getBlockStringIndentation([])).to.equal(0);
+  it('returns zero for an empty string', () => {
+    expect(getBlockStringIndentation('')).to.equal(0);
   });
 
   it('do not take first line into account', () => {
-    expect(getBlockStringIndentation(['  a'])).to.equal(0);
-    expect(getBlockStringIndentation([' a', '  b'])).to.equal(2);
+    expect(getBlockStringIndentation('  a')).to.equal(0);
+    expect(getBlockStringIndentation(' a\n  b')).to.equal(2);
   });
 
   it('returns minimal indentation length', () => {
-    expect(getBlockStringIndentation(['', ' a', '  b'])).to.equal(1);
-    expect(getBlockStringIndentation(['', '  a', ' b'])).to.equal(1);
-    expect(getBlockStringIndentation(['', '  a', ' b', 'c'])).to.equal(0);
+    expect(getBlockStringIndentation('\n a\n  b')).to.equal(1);
+    expect(getBlockStringIndentation('\n  a\n b')).to.equal(1);
+    expect(getBlockStringIndentation('\n  a\n b\nc')).to.equal(0);
   });
 
   it('count both tab and space as single character', () => {
-    expect(getBlockStringIndentation(['', '\ta', '          b'])).to.equal(1);
-    expect(getBlockStringIndentation(['', '\t a', '          b'])).to.equal(2);
-    expect(getBlockStringIndentation(['', ' \t a', '          b'])).to.equal(3);
+    expect(getBlockStringIndentation('\n\ta\n          b')).to.equal(1);
+    expect(getBlockStringIndentation('\n\t a\n          b')).to.equal(2);
+    expect(getBlockStringIndentation('\n \t a\n          b')).to.equal(3);
   });
 
   it('do not take empty lines into account', () => {
-    expect(getBlockStringIndentation(['a', '\t'])).to.equal(0);
-    expect(getBlockStringIndentation(['a', ' '])).to.equal(0);
-    expect(getBlockStringIndentation(['a', ' ', '  b'])).to.equal(2);
-    expect(getBlockStringIndentation(['a', ' ', '  b'])).to.equal(2);
-    expect(getBlockStringIndentation(['a', '', ' b'])).to.equal(1);
+    expect(getBlockStringIndentation('a\n ')).to.equal(0);
+    expect(getBlockStringIndentation('a\n\t')).to.equal(0);
+    expect(getBlockStringIndentation('a\n\n b')).to.equal(1);
+    expect(getBlockStringIndentation('a\n \n  b')).to.equal(2);
   });
 });
 

src/language/blockString.d.ts

@@ -9,7 +9,7 @@ export function dedentBlockStringValue(rawString: string): string;
 /**
  * @internal
  */
-export function getBlockStringIndentation(lines: ReadonlyArray<string>): number;
+export function getBlockStringIndentation(body: string): number;
 
 /**
  * Print a block string in the indented block form by adding a leading and

src/language/blockString.js

@@ -11,7 +11,7 @@ export function dedentBlockStringValue(rawString: string): string {
   const lines = rawString.split(/\r\n|[\n\r]/g);
 
   // Remove common indentation from all lines but first.
-  const commonIndent = getBlockStringIndentation(lines);
+  const commonIndent = getBlockStringIndentation(rawString);
 
   if (commonIndent !== 0) {
     for (let i = 1; i < lines.length; i++) {
@@ -20,52 +20,68 @@ export function dedentBlockStringValue(rawString: string): string {
   }
 
   // Remove leading and trailing blank lines.
-  while (lines.length > 0 && isBlank(lines[0])) {
-    lines.shift();
+  let startLine = 0;
+  while (startLine < lines.length && isBlank(lines[startLine])) {
+    ++startLine;
   }
-  while (lines.length > 0 && isBlank(lines[lines.length - 1])) {
-    lines.pop();
+
+  let endLine = lines.length;
+  while (endLine > startLine && isBlank(lines[endLine - 1])) {
+    --endLine;
   }
 
   // Return a string of the lines joined with U+000A.
-  return lines.join('\n');
+  return lines.slice(startLine, endLine).join('\n');
 }
+
+function isBlank(str) {
+  for (let i = 0; i < str.length; ++i) {
+    if (str[i] !== ' ' && str[i] !== '\t') {
+      return false;
+    }
+  }
+
+  return true;
+}
+
 /**
  * @internal
  */
-export function getBlockStringIndentation(
-  lines: $ReadOnlyArray<string>,
-): number {
+export function getBlockStringIndentation(value: string): number {
+  let isFirstLine = true;
+  let isEmptyLine = true;
+  let indent = 0;
   let commonIndent = null;
 
-  for (let i = 1; i < lines.length; i++) {
-    const line = lines[i];
-    const indent = leadingWhitespace(line);
-    if (indent === line.length) {
-      continue; // skip empty lines
-    }
-
-    if (commonIndent === null || indent < commonIndent) {
-      commonIndent = indent;
-      if (commonIndent === 0) {
+  for (let i = 0; i < value.length; ++i) {
+    switch (value.charCodeAt(i)) {
+      case 13: //  \r
+        if (value.charCodeAt(i + 1) === 10) {
+          ++i; // skip \r\n as one symbol
+        }
+      // falls through
+      case 10: //  \n
+        isFirstLine = false;
+        isEmptyLine = true;
+        indent = 0;
+        break;
+      case 9: //   \t
+      case 32: //  <space>
+        ++indent;
         break;
-      }
+      default:
+        if (
+          isEmptyLine &&
+          !isFirstLine &&
+          (commonIndent === null || indent < commonIndent)
+        ) {
+          commonIndent = indent;
+        }
+        isEmptyLine = false;
     }
   }
 
-  return commonIndent === null ? 0 : commonIndent;
-}
-
-function leadingWhitespace(str) {
-  let i = 0;
-  while (i < str.length && (str[i] === ' ' || str[i] === '\t')) {
-    i++;
-  }
-  return i;
-}
-
-function isBlank(str) {
-  return leadingWhitespace(str) === str.length;
+  return commonIndent ?? 0;
 }
 
 /**

src/utilities/stripIgnoredCharacters.js

@@ -107,8 +107,7 @@ function dedentBlockString(blockStr) {
   const rawStr = blockStr.slice(3, -3);
   let body = dedentBlockStringValue(rawStr);
 
-  const lines = body.split(/\r\n|[\n\r]/g);
-  if (getBlockStringIndentation(lines) > 0) {
+  if (getBlockStringIndentation(body) > 0) {
     body = '\n' + body;
   }