introduce enforce-min-coverage rule

src/collect.js

@@ -185,6 +185,52 @@ function executeFlow(stdin, root, filepath) {
     : true;
 }
 
+export function coverage(stdin, root, filepath) {
+  let stdout;
+
+  switch (stdin && root && filepath && stdin !== '') {
+    case true:
+      stdout = childProcess.spawnSync(getFlowBin(), [
+        'coverage',
+        '--json',
+        `--root=${root}`,
+        filepath
+      ], {
+        input: stdin,
+        encoding: 'utf-8'
+      }).stdout;
+      break;
+    default:
+      stdout = childProcess.spawnSync(getFlowBin(), ['--json']).stdout;
+  }
+
+  //
+  // This serves as a temporary HACK to prevent 32 bit OS's from failing. Flow does not
+  // support 32 bit OS's at the moment.
+  // This pretends as if there are now flow errors
+  //
+  // Ideally, there would be a preinstall npm event to check if the user is on a 32 bit OS
+  //
+
+  if (!stdout) {
+    return true;
+  }
+
+  const stringifiedStdout = stdout.toString();
+  let parsedJSON;
+
+  try {
+    parsedJSON = JSON.parse(stringifiedStdout);
+  } catch (e) {
+    parsedJSON = fatalError(stringifiedStdout);
+  }
+
+  return {
+    coveredCount: parsedJSON.expressions.covered_count,
+    uncoveredCount: parsedJSON.expressions.uncovered_count
+  };
+}
+
 export default function collect(stdin, root, filepath) {
   return executeFlow(stdin, root, filepath);
 }

src/index.js

@@ -1,6 +1,6 @@
 import path from 'path';
 import fs from 'fs';
-import collect from './collect';
+import collect, { coverage } from './collect';
 
 
 let runOnAllFiles;
@@ -11,8 +11,48 @@ function hasFlowPragma(source) {
     .some(comment => /@flow/.test(comment.value));
 }
 
+function lookupFlowDir(context) {
+  const root = process.cwd();
+  const flowDirSetting = context.settings
+    && context.settings['flowtype-errors']
+    && context.settings['flowtype-errors'].flowDir || '.';
+
+  return fs.existsSync(path.join(root, flowDirSetting, '.flowconfig'))
+    ? path.join(root, flowDirSetting)
+    : root;
+}
+
 export default {
   rules: {
+    'enforce-min-coverage': function enforceMinCoverage(context) {
+      return {
+        Program() {
+          const source = context.getSourceCode();
+          const flowDir = lookupFlowDir(context);
+          const requiredCoverage = context.options[0];
+
+          if (hasFlowPragma(source)) {
+            const res = coverage(source.getText(), flowDir, context.getFilename());
+
+            if (res === true) {
+              return;
+            }
+
+            const { coveredCount, uncoveredCount } = res;
+
+            /* eslint prefer-template: 0 */
+            const percentage = Number(Math.round((coveredCount / (coveredCount + uncoveredCount)) * 100 + 'e2') + 'e-2');
+
+            if (percentage < requiredCoverage) {
+              context.report({
+                loc: 1,
+                message: `Expected coverage to be at least ${requiredCoverage}%, but is: ${percentage}%`
+              });
+            }
+          }
+        }
+      };
+    },
     'show-errors': function showErrors(context) {
       return {
         Program() {
@@ -21,14 +61,7 @@ export default {
 
           if (onTheFly) {
             const source = context.getSourceCode();
-            const root = process.cwd();
-            const flowDirSetting = context.settings
-              && context.settings['flowtype-errors']
-              && context.settings['flowtype-errors'].flowDir || '.';
-
-            const flowDir = fs.existsSync(path.join(root, flowDirSetting, '.flowconfig'))
-              ? path.join(root, flowDirSetting)
-              : root;
+            const flowDir = lookupFlowDir(context);
 
             // Check to see if we should run on every file
             if (runOnAllFiles === undefined) {

test/__snapshots__/format.spec.js.snap

@@ -1,3 +1,27 @@
+exports[`Check codebases coverage-fail - eslint should give expected output 1`] = `
+"
+./example.js
+  0:0  error  Expected coverage to be at least 50%, but is: 0%  flowtype-errors/enforce-min-coverage
+
+✖ 1 problem (1 error, 0 warnings)
+
+"
+`;
+
+exports[`Check codebases coverage-fail2 - eslint should give expected output 1`] = `
+"
+./example.js
+  0:0  error  Expected coverage to be at least 50%, but is: 33.33%  flowtype-errors/enforce-min-coverage
+
+✖ 1 problem (1 error, 0 warnings)
+
+"
+`;
+
+exports[`Check codebases coverage-ok - eslint should give expected output 1`] = `""`;
+
+exports[`Check codebases coverage-ok2 - eslint should give expected output 1`] = `""`;
+
 exports[`Check codebases flow-pragma-1 - eslint should give expected output 1`] = `
 "
 ./example.js

test/codebases/coverage-fail/example.js

@@ -0,0 +1,3 @@
+// @flow
+
+let x;

test/codebases/coverage-fail2/example.js

@@ -0,0 +1,5 @@
+// @flow
+
+let x: number;
+let y;
+let z;

test/codebases/coverage-ok/example.js

@@ -0,0 +1,3 @@
+// @flow
+
+let x: number = 100;

test/codebases/coverage-ok2/example.js

@@ -0,0 +1,5 @@
+// @flow
+
+let x: number;
+let y: number;
+let z;

test/format.spec.js

@@ -69,7 +69,11 @@ const codebases = [
   'no-flow-pragma',
   'project-1',
   'run-all',
-  'run-all-flowdir'
+  'run-all-flowdir',
+  'coverage-ok',
+  'coverage-ok2',
+  'coverage-fail',
+  'coverage-fail2'
 ];
 
 const issue81 = process.platform === 'win32' ? 'folder with spaces' : 'folder-with-spaces';
@@ -80,7 +84,7 @@ try {
   // Already exists
 }
 
-const eslintConfig = `
+const eslintConfig = (enforceMinCoverage) => `
   var Module = require('module');
   var path = require('path');
   var original = Module._resolveFilename;
@@ -107,7 +111,12 @@ const eslintConfig = `
       }
     },
     rules: {
-      'flowtype-errors/show-errors': 2
+      ${enforceMinCoverage ? `
+        'flowtype-errors/show-errors': 2,
+        'flowtype-errors/enforce-min-coverage': [2, ${enforceMinCoverage}]
+      ` : `
+        'flowtype-errors/show-errors': 2
+      `}
     }
   };
 `;
@@ -130,7 +139,7 @@ describe('Check codebases', () => {
       const configPath = path.resolve(fullFolder, '.eslintrc.js');
 
       // Write config file
-      writeFileSync(configPath, eslintConfig);
+      writeFileSync(configPath, eslintConfig(folder.match(/^coverage-/) ? 50 : 0));
 
       // Spawn a eslint process
       const { stdout, stderr } = runEslint(fullFolder);