fix: issue with preserving new line characters in read-rule

.babelrc

@@ -1,20 +1,20 @@
 {
-  ignore: [
-    '__mocks__',
-    '__tests__',
-    '__test_support__',
-    '/coverage',
+  "ignore": [
+    "__mocks__",
+    "__tests__",
+    "__test_support__",
+    "/coverage"
   ],
-  presets: [
-    ['env', {
-      targets: {
-        node: 6,
-      },
-    }],
+  "presets": [
+    ["env", {
+      "targets": {
+        "node": 6
+      }
+    }]
   ],
-  env: {
-    test: {
-      ignore: null
+  "env": {
+    "test": {
+      "ignore": null
     }
   }
 }

.gitignore

@@ -1,3 +1,4 @@
 node_modules
 coverage
 lib
+.idea

.npmignore

@@ -1,3 +1,4 @@
 # If `lib` is ignored, then npm won’t publish it.
 coverage
 __tests__
+__mocks__

src/actions/__tests__/read-rule.test.js

@@ -74,4 +74,45 @@ describe('readRule()', () => {
       runReadRule(undefined, docs.replace('\n', '\r\n')).newDocs
     ).toMatchSnapshot()
   })
+
+  it('mixed windows and unix newlines', () => {
+    const docs = `# ${description} (${name})\nSome random test:\r\n\r\n`
+
+    expect(runReadRule(undefined, docs).newDocs).toBe(docs)
+  })
+
+  it('whitespaces before heading', () => {
+    const docs = `\n\n\n\n\r\n# ${description} (${name})\n`
+    const outputDocs = `# ${description} (${name})\n`
+
+    expect(runReadRule(undefined, docs).newDocs).toBe(outputDocs)
+  })
+
+  it('non string text before heading', () => {
+    const docs = `\nTest\n`
+    const outputDocs = `# ${description} (${name})\n\nTest\n`
+
+    expect(runReadRule(undefined, docs).newDocs).toBe(outputDocs)
+  })
+
+  it('non string text before heading without new line', () => {
+    const docs = `Test\n`
+    const outputDocs = `# ${description} (${name})\nTest\n`
+
+    expect(runReadRule(undefined, docs).newDocs).toBe(outputDocs)
+  })
+
+  it('single line heading', () => {
+    const docs = `# Test`
+    const outputDocs = `# ${description} (${name})`
+
+    expect(runReadRule(undefined, docs).newDocs).toBe(outputDocs)
+  })
+
+  it('empty file', () => {
+    const docs = ``
+    const outputDocs = `# ${description} (${name})\n`
+
+    expect(runReadRule(undefined, docs).newDocs).toBe(outputDocs)
+  })
 })

src/actions/read-rule.js

@@ -15,11 +15,13 @@ module.exports = ({ rule, docs, friendlyDocPath }, name) => {
   const fixable = rule.meta.fixable
   const { description, extraDescription, recommended } = rule.meta.docs
 
-  const nl = detectNewline(docs)
+  const heading = `# ${description} (${name})`
 
-  const newDocs = [`# ${description} (${name})`]
-    .concat(docs.split(nl).slice(1))
-    .join(nl)
+  const regTest = /^\s*#[^\r\n]*(\r?\n)?/
+
+  const newDocs = regTest.test(docs)
+    ? docs.replace(regTest, heading + `$1`)
+    : `${heading}${detectNewline(docs)}${docs}`
 
   if (newDocs !== docs) {
     const patch = diff(friendlyDocPath, 'generated', docs, newDocs)