Infer type for variable declarations and class properties (documentationjs#540)

This infers the type from Flow type annotations for variable
declarations and class properties.

This also moves the logic for setting the `type` for typedefs
to the same type inferrer.

Also infer the type for statements like:

```js
const x = 42;
```

same as:

```js
const x: number = 42;
```

Author: arv

index.js

@@ -20,7 +20,7 @@ var fs = require('fs'),
   inferMembership = require('./lib/infer/membership'),
   inferReturn = require('./lib/infer/return'),
   inferAccess = require('./lib/infer/access'),
-  inferTypedefType = require('./lib/infer/typedef_type'),
+  inferType = require('./lib/infer/type'),
   formatLint = require('./lib/lint').formatLint,
   garbageCollect = require('./lib/garbage_collect'),
   lintComments = require('./lib/lint').lintComments,
@@ -175,7 +175,7 @@ function buildSync(indexes, options) {
     inferProperties(),
     inferReturn(),
     inferMembership(),
-    inferTypedefType(),
+    inferType(),
     nest,
     options.github && github,
     garbageCollect);
@@ -245,7 +245,7 @@ function lint(indexes, options, callback) {
     inferProperties(),
     inferReturn(),
     inferMembership(),
-    inferTypedefType(),
+    inferType(),
     nest);
 
   return expandInputs(indexes, options, function (error, inputs) {

lib/infer/finders.js

@@ -22,9 +22,9 @@ function findTarget(path) {
     path = path.declaration;
   }
 
-  // var x = TARGET;
+  // var x = init;
   if (t.isVariableDeclaration(path)) {
-    return path.declarations[0].init;
+    return path.declarations[0];
   }
 
   // foo.x = TARGET

lib/infer/params.js

@@ -162,6 +162,12 @@ function inferParams() {
   return shouldSkipInference(function inferParams(comment) {
     var node = finders.findTarget(comment.context.ast);
 
+    // In case of `/** */ var x = function () {}` findTarget returns
+    // the declarator.
+    if (t.isVariableDeclarator(node)) {
+      node = node.init;
+    }
+
     if (!t.isFunction(node)) {
       return comment;
     }

lib/infer/type.js

@@ -0,0 +1,55 @@
+'use strict';
+
+var finders = require('./finders'),
+  shouldSkipInference = require('./should_skip_inference'),
+  flowDoctrine = require('../flow_doctrine'),
+  t = require('babel-types');
+
+var constTypeMapping = {
+  'BooleanLiteral': {type: 'BooleanTypeAnnotation'},
+  'NumericLiteral': {type: 'NumberTypeAnnotation'},
+  'StringLiteral': {type: 'StringTypeAnnotation'}
+};
+
+/**
+ * Infers type tags by using Flow type annotations
+ *
+ * @name inferType
+ * @param {Object} comment parsed comment
+ * @returns {Object} comment with type tag inferred
+ */
+module.exports = function () {
+  return shouldSkipInference(function inferType(comment) {
+    if (comment.type) {
+      return comment;
+    }
+
+    var n = finders.findTarget(comment.context.ast);
+    if (!n) {
+      return comment;
+    }
+
+    var type;
+    switch (n.type) {
+    case 'VariableDeclarator':
+      type = n.id.typeAnnotation;
+      if (!type && comment.kind === 'constant') {
+        type = constTypeMapping[n.init.type];
+      }
+      break;
+    case 'ClassProperty':
+      type = n.typeAnnotation;
+      break;
+    case 'TypeAlias':
+      type = n.right;
+      break;
+    }
+    if (type) {
+      if (t.isTypeAnnotation(type)) {
+        type = type.typeAnnotation;
+      }
+      comment.type = flowDoctrine(type);
+    }
+    return comment;
+  });
+};

lib/infer/typedef_type.js

@@ -21,6 +21,22 @@ test('inferParams', function (t) {
     function f(x) {}
   }).params, [{lineNumber: 3, name: 'x', title: 'param'}]);
 
+  t.deepEqual(evaluate(function () {
+    /** Test */
+    var f = function (x) {};
+  }).params, [{lineNumber: 3, name: 'x', title: 'param'}]);
+
+  t.deepEqual(evaluate('/** Test */ var f = (x) => {}').params,
+    [{lineNumber: 1, name: 'x', title: 'param'}]);
+
+  t.deepEqual(evaluate(function () {
+    var x = 1,
+      g = function (y) {},
+      /** Test */
+      f = function (x) {};
+  }).params, [{lineNumber: 5, name: 'x', title: 'param'}]);
+
+
   t.deepEqual(evaluate('/** Test */ export function f(x) {}').params,
     [{lineNumber: 1, name: 'x', title: 'param'}]);
 

test/lib/infer/params.js

@@ -0,0 +1,135 @@
+'use strict';
+
+var test = require('tap').test,
+  parse = require('../../../lib/parsers/javascript'),
+  inferKind = require('../../../lib/infer/kind')(),
+  inferType = require('../../../lib/infer/type')();
+
+function toComment(code) {
+  return parse({
+    source: code
+  })[0];
+}
+
+function evaluate(code) {
+  return inferType(inferKind(toComment(code)));
+}
+
+test('inferType', function (t) {
+  t.deepEqual(evaluate(
+    '/** @typedef {T} V */'
+  ).type, {
+    name: 'T',
+    type: 'NameExpression'
+  });
+
+  t.deepEqual(evaluate(
+    '/** */' +
+    'type V = T'
+  ).type, {
+    name: 'T',
+    type: 'NameExpression'
+  });
+
+  t.deepEqual(evaluate(
+    '/** @typedef {Array<T>} V */'
+  ).type, {
+    applications: [
+      {
+        name: 'T',
+        type: 'NameExpression'
+      }
+    ],
+    expression: {
+      name: 'Array',
+      type: 'NameExpression'
+    },
+    type: 'TypeApplication'
+  });
+
+  t.deepEqual(evaluate(
+    '/** */' +
+    'type V = Array<T>'
+  ).type, {
+    applications: [
+      {
+        name: 'T',
+        type: 'NameExpression'
+      }
+    ],
+    expression: {
+      name: 'Array',
+      type: 'NameExpression'
+    },
+    type: 'TypeApplication'
+  });
+
+  t.deepEqual(evaluate(
+    '/** */' +
+    'var x: number'
+  ).type, {
+    name: 'number',
+    type: 'NameExpression'
+  });
+
+  t.deepEqual(evaluate(
+    '/** */' +
+    'let x: number'
+  ).type, {
+    name: 'number',
+    type: 'NameExpression'
+  });
+
+  t.deepEqual(evaluate(
+    '/** */' +
+    'const x: number = 42;'
+  ).type, {
+    name: 'number',
+    type: 'NameExpression'
+  });
+
+  t.deepEqual(evaluate(
+    'let x,' +
+    '/** */' +
+    'y: number'
+  ).type, {
+    name: 'number',
+    type: 'NameExpression'
+  });
+
+  t.deepEqual(evaluate(
+    'class C {' +
+    '/** */' +
+    'x: number;' +
+    '}'
+  ).type, {
+    name: 'number',
+    type: 'NameExpression'
+  });
+
+  t.deepEqual(evaluate(
+    '/** */' +
+    'const x = 42;'
+  ).type, {
+    name: 'number',
+    type: 'NameExpression'
+  });
+
+  t.deepEqual(evaluate(
+    '/** */' +
+    'const x = "abc";'
+  ).type, {
+    name: 'string',
+    type: 'NameExpression'
+  });
+
+  t.deepEqual(evaluate(
+    '/** */' +
+    'const x = true;'
+  ).type, {
+    name: 'boolean',
+    type: 'NameExpression'
+  });
+
+  t.end();
+});