feat: add new rule enforce-line-break (#484)

* feat: add new rule enforce-line-break

* feat: edit new rule enforce line break - don't add line if comments above type declaration is on the 1st line, update tests

* fix: clean up code

* fix: change message - enforceLineBreak

Co-authored-by: Angelica Bocanegra <angelica.bocanegra@tabcorp.com.au>

.README/README.md

@@ -160,6 +160,7 @@ When `true`, only checks files with a [`@flow` annotation](http://flowtype.org/d
 {"gitdown": "include", "file": "./rules/boolean-style.md"}
 {"gitdown": "include", "file": "./rules/define-flow-type.md"}
 {"gitdown": "include", "file": "./rules/delimiter-dangle.md"}
+{"gitdown": "include", "file": "./rules/enforce-line-break.md"}
 {"gitdown": "include", "file": "./rules/generic-spacing.md"}
 {"gitdown": "include", "file": "./rules/newline-after-flow-annotation.md"}
 {"gitdown": "include", "file": "./rules/no-dupe-keys.md"}

.README/rules/enforce-line-break.md

@@ -0,0 +1,5 @@
+### `enforce-line-break`
+
+This rule enforces line breaks between type definitions.
+
+<!-- assertions enforceLineBreak -->

README.md

@@ -22,6 +22,7 @@
         * [`boolean-style`](#eslint-plugin-flowtype-rules-boolean-style)
         * [`define-flow-type`](#eslint-plugin-flowtype-rules-define-flow-type)
         * [`delimiter-dangle`](#eslint-plugin-flowtype-rules-delimiter-dangle)
+        * [`enforce-line-break`](#eslint-plugin-flowtype-rules-enforce-line-break)
         * [`generic-spacing`](#eslint-plugin-flowtype-rules-generic-spacing)
         * [`newline-after-flow-annotation`](#eslint-plugin-flowtype-rules-newline-after-flow-annotation)
         * [`no-dupe-keys`](#eslint-plugin-flowtype-rules-no-dupe-keys)
@@ -1662,6 +1663,83 @@ type X = []
 
 
 
+<a name="eslint-plugin-flowtype-rules-enforce-line-break"></a>
+### <code>enforce-line-break</code>
+
+This rule enforces line breaks between type definitions.
+
+The following patterns are considered problems:
+
+```js
+type baz = 6;
+const hi = 2;
+// Message: New line required below type declaration
+
+const foo = 6;
+type hi = 2;
+
+// Message: New line required above type declaration
+
+const som = "jes";
+// a comment
+type fed = "hed";
+
+// Message: New line required above type declaration
+
+type som = "jes";
+// a comment
+const fed = "hed";
+
+// Message: New line required below type declaration
+
+type hello = 34;
+const som = "jes";
+type fed = "hed";
+
+// Message: New line required below type declaration
+// Message: New line required above type declaration
+```
+
+The following patterns are not considered problems:
+
+```js
+type gjs = 6;
+
+type gjs = 6;
+
+type hi = 2;
+
+
+type X = 4;
+
+const red = "serpent";
+console.log("hello");
+
+// number or string
+type Y = string | number;
+
+// resting + sleep
+type snooze = "dreaming" | "";
+
+type Props = {
+  accountBalance: string | number,
+  accountNumber: string | number,
+};
+
+const x = 4;
+const y = 489;
+
+// Some Comment
+type Props = {
+  accountBalance: string | number,
+  accountNumber: string | number,
+};
+
+type RoadT = "grass" | "gravel" | "cement";
+```
+
+
+
 <a name="eslint-plugin-flowtype-rules-generic-spacing"></a>
 ### <code>generic-spacing</code>
 

src/index.js

@@ -6,6 +6,7 @@ import arrayStyleSimpleType from './rules/arrayStyleSimpleType';
 import booleanStyle from './rules/booleanStyle';
 import defineFlowType from './rules/defineFlowType';
 import delimiterDangle from './rules/delimiterDangle';
+import enforceLineBreak from './rules/enforceLineBreak';
 import genericSpacing from './rules/genericSpacing';
 import newlineAfterFlowAnnotation from './rules/newlineAfterFlowAnnotation';
 import noDupeKeys from './rules/noDupeKeys';
@@ -53,6 +54,7 @@ const rules = {
   'boolean-style': booleanStyle,
   'define-flow-type': defineFlowType,
   'delimiter-dangle': delimiterDangle,
+  'enforce-line-break': enforceLineBreak,
   'generic-spacing': genericSpacing,
   'newline-after-flow-annotation': newlineAfterFlowAnnotation,
   'no-dupe-keys': noDupeKeys,

src/rules/enforceLineBreak.js

@@ -0,0 +1,63 @@
+const schema = [];
+
+const breakLineMessage = (direction) => {
+  return `New line required ${direction} type declaration`;
+};
+
+const create = (context) => {
+  return {
+    TypeAlias (node) {
+      const sourceCode = context.getSourceCode();
+      if (sourceCode.lines.length === 1) {
+        return;
+      }
+
+      if (node.loc.start.line !== 1) {
+        if (node.leadingComments && node.leadingComments[0].loc.start.line !== 1) {
+          const lineAboveComment = sourceCode.lines[node.leadingComments[0].loc.start.line - 2];
+          if (lineAboveComment !== '') {
+            context.report({
+              fix (fixer) {
+                return fixer.insertTextBeforeRange(node.leadingComments[0].range, '\n');
+              },
+              message: breakLineMessage('above'),
+              node,
+            });
+          }
+        } else if (!node.leadingComments) {
+          const isLineAbove = sourceCode.lines[node.loc.start.line - 2];
+          if (isLineAbove !== '') {
+            context.report({
+              fix (fixer) {
+                return fixer.insertTextBefore(node, '\n');
+              },
+              message: breakLineMessage('above'),
+              node,
+            });
+          }
+        }
+      }
+
+      if (sourceCode.lines.length !== node.loc.end.line) {
+        const isLineBelow = sourceCode.lines[node.loc.end.line];
+        if (isLineBelow !== '') {
+          context.report({
+            fix (fixer) {
+              return fixer.insertTextAfter(node, '\n');
+            },
+            message: breakLineMessage('below'),
+            node,
+          });
+        }
+      }
+    },
+  };
+};
+
+export default {
+  create,
+  meta: {
+    fixable: 'code',
+  },
+  schema,
+};

tests/rules/assertions/enforceLineBreak.js

@@ -0,0 +1,81 @@
+export default {
+  invalid: [
+    {
+      code: 'type baz = 6;\nconst hi = 2;',
+      errors: [{
+        message: 'New line required below type declaration',
+      }],
+      output: 'type baz = 6;\n\nconst hi = 2;',
+    },
+    {
+      code: 'const foo = 6;\ntype hi = 2;\n',
+      errors: [
+        {message: 'New line required above type declaration'},
+      ],
+      output: 'const foo = 6;\n\ntype hi = 2;\n',
+    },
+    {
+      code: 'const som = "jes";\n// a comment\ntype fed = "hed";\n',
+      errors: [
+        {message: 'New line required above type declaration'},
+      ],
+      output: 'const som = "jes";\n\n// a comment\ntype fed = "hed";\n',
+    },
+    {
+      code: 'type som = "jes";\n// a comment\nconst fed = "hed";\n',
+      errors: [
+        {message: 'New line required below type declaration'},
+      ],
+      output: 'type som = "jes";\n\n// a comment\nconst fed = "hed";\n',
+    },
+    {
+      code: 'type hello = 34;\nconst som = "jes";\ntype fed = "hed";\n',
+      errors: [
+        {message: 'New line required below type declaration'},
+        {message: 'New line required above type declaration'},
+      ],
+      output: 'type hello = 34;\n\nconst som = "jes";\n\ntype fed = "hed";\n',
+    },
+  ],
+  valid: [
+    {
+      code: 'type gjs = 6;',
+    },
+    {
+      code: 'type gjs = 6;\n\ntype hi = 2;\n',
+    },
+    {
+      code:
+`type X = 4;
+
+const red = "serpent";
+console.log("hello");
+
+// number or string
+type Y = string | number;
+
+// resting + sleep
+type snooze = "dreaming" | "";`,
+    },
+    {
+      code:
+`type Props = {
+  accountBalance: string | number,
+  accountNumber: string | number,
+};`,
+    },
+    {
+      code:
+`const x = 4;
+const y = 489;
+
+// Some Comment
+type Props = {
+  accountBalance: string | number,
+  accountNumber: string | number,
+};
+
+type RoadT = "grass" | "gravel" | "cement";`,
+    },
+  ],
+};

tests/rules/index.js

@@ -17,6 +17,7 @@ const reportingRules = [
   'boolean-style',
   'define-flow-type',
   'delimiter-dangle',
+  'enforce-line-break',
   'generic-spacing',
   'newline-after-flow-annotation',
   'no-dupe-keys',