feat: allow line break to satisfy trailing space rule

.README/rules/space-after-type-colon.md

@@ -4,6 +4,28 @@ _The `--fix` option on the command line automatically fixes problems reported by
 
 Enforces consistent spacing after the type annotation colon.
 
-This rule takes one argument. If it is `'always'` then a problem is raised when there is no space after the type annotation colon. If it is `'never'` then a problem is raised when there is a space after the type annotation colon. The default value is `'always'`.
+#### Options
+
+This rule has a string argument.
+
+* `"always"` (default): Require a space after the type annotation colon (e.g. foo: BarType).
+* `"never"`: Require no spaces after the type annotation colon (e.g. foo:BarType).
+
+This rule has an option object.
+
+* `"allowLineBreak"` - Allow a line break to count as a space following the annotation colon.
+    * `"true"`: Enable
+    * `"false"`: Disable
+
+{
+  "rules": {
+    "flowtype/space-after-type-colon": [
+      2,
+      "always", {
+        "allowLineBreak": false
+      }
+    ]
+  }
+}
 
 <!-- assertions spaceAfterTypeColon -->

src/rules/spaceAfterTypeColon.js

@@ -1,7 +1,9 @@
+import _ from 'lodash';
 import makeSpacing from './typeColonSpacing';
 
 export default (context) => {
   return makeSpacing('after', context, {
-    always: (context.options[0] || 'always') === 'always'
+    allowLineBreak: _.get(context, ['options', '1', 'allowLineBreak'], false),
+    always: _.get(context, ['options', '0'], 'always') === 'always'
   });
 };

src/rules/typeColonSpacing/reporter.js

@@ -10,15 +10,24 @@ const getSpaces = (direction, colon, context) => {
   }
 };
 
-export default (direction, context, {always}) => {
+export default (direction, context, {always, allowLineBreak}) => {
   return ({colon, node, name = '', type = 'type annotation'}) => {
-    const spaces = getSpaces(direction, colon, context);
+    let spaces;
+
     const data = {
       direction,
       name,
       type
     };
 
+    const charAfter = context.getSourceCode().getText(colon, 0, 1).slice(1);
+
+    if (allowLineBreak && (charAfter === '\n' || charAfter === '\r\n')) {
+      spaces = 1;
+    } else {
+      spaces = getSpaces(direction, colon, context);
+    }
+
     if (always && spaces > 1) {
       context.report({
         data,

tests/rules/assertions/spaceAfterTypeColon.js

@@ -67,6 +67,11 @@ const ARROW_FUNCTION_PARAMS = {
       errors: [{message: 'There must be no space after "i" parameter type annotation colon.'}],
       options: ['never'],
       output: '(i?:number) => {}'
+    },
+    {
+      code: '(foo:\n  { a: string, b: number }) => {}',
+      errors: [{message: 'There must be 1 space after "foo" parameter type annotation colon.'}],
+      output: '(foo: { a: string, b: number }) => {}'
     }
   ],
   valid: [
@@ -113,6 +118,12 @@ const ARROW_FUNCTION_PARAMS = {
     {
       code: '(i?:number) => {}',
       options: ['never']
+    },
+    {
+      code: '(foo:\n  { a: string, b: number }) => {}',
+      options: ['always', {
+        allowLineBreak: true
+      }]
     }
   ]
 };