tools: add lint fixer for require-buffer

Adds `require-buffer` lint fixer. If the buffer module is not required while `Buffer` is used, require the `buffer` module. If the file has a `'use strict';` line, add the require after it on a separate line. If the file does not have any (currently impossible with the `strict` rule) add it after the first comment (before the real code starts). Fixes: #16636 PR-URL: #17144 Reviewed-By: Michaël Zasso <[email protected]>

Author: Bamieh

test/parallel/test-eslint-require-buffer.js

@@ -12,15 +12,36 @@ const ruleTester = new RuleTester({
 constmessage="Use const Buffer = require('buffer').Buffer; "+
 'at the beginning of this file';
 
+constuseStrict='\'use strict\'\n\n';
+constbufferModule='const{Buffer } = require(\'buffer\');\n';
+constmockComment='// Some Comment\n//\n// Another Comment\n\n';
+constuseBuffer='Buffer;';
 ruleTester.run('require-buffer',rule,{
 valid: [
 'foo',
-'const Buffer = require("Buffer"); Buffer;'
+'const Buffer = require("Buffer"); Buffer;',
+'const{Buffer } = require(\'buffer\'); Buffer;',
 ],
 invalid: [
 {
-code: 'Buffer;',
-errors: [{ message }]
-}
+code: useBuffer,
+errors: [{ message }],
+output: bufferModule+useBuffer,
+},
+{
+code: useStrict+useBuffer,
+errors: [{ message }],
+output: useStrict+bufferModule+useBuffer,
+},
+{
+code: mockComment+useBuffer,
+errors: [{ message }],
+output: mockComment+bufferModule+useBuffer,
+},
+{
+code: mockComment+useStrict+useBuffer,
+errors: [{ message }],
+output: mockComment+useStrict+bufferModule+useBuffer,
+},
 ]
 });

tools/eslint-rules/require-buffer.js

@@ -1,10 +1,26 @@
 'use strict';
+constBUFFER_REQUIRE='const{Buffer } = require(\'buffer\');\n';
 
 module.exports=function(context){
+
 functionflagIt(reference){
 constmsg='Use const Buffer = require(\'buffer\').Buffer; '+
 'at the beginning of this file';
-context.report(reference.identifier,msg);
+
+context.report({
+node: reference.identifier,
+message: msg,
+fix: (fixer)=>{
+constsourceCode=context.getSourceCode();
+
+constuseStrict=/'usestrict';\n\n?/g;
+consthasUseStrict=!!useStrict.exec(sourceCode.text);
+constfirstLOC=sourceCode.ast.range[0];
+constrangeNeedle=hasUseStrict ? useStrict.lastIndex : firstLOC;
+
+returnfixer.insertTextBeforeRange([rangeNeedle],BUFFER_REQUIRE);
+}
+});
 }
 
 return{