feat: switch to the CS2 AST format (#317)

There's some CS2-specific code, but we don't yet ever run the CS2 parser.
Instead, we run the CS1 parser, convert that AST to a CS2 AST, then convert that
to a decaffeinate-parser AST. This should make it possible to variably use the
CS1 or CS2 parser depending on configuration.

BREAKING CHANGE: Node 4 is no longer supported. The returned CoffeeScript AST is
now a CS2 AST, and there are slight differences in ranges and AST structure for
comment-only blocks.

Author: alangpierce

.travis.yml

@@ -10,7 +10,6 @@ node_js:
   - '9'
   - '8'
   - '6'
-  - '4'
 before_install:
   # TODO: Switch this back to yarn when greenkeeperio/greenkeeper-lockfile#98 is fixed.
   # https://github.com/greenkeeperio/greenkeeper-lockfile/issues/98

package.json

@@ -22,10 +22,14 @@
   "files": [
     "dist/"
   ],
+  "engines": {
+    "node": ">=6"
+  },
   "dependencies": {
     "babylon": "^6.18.0",
     "coffee-lex": "^8.1.1",
     "decaffeinate-coffeescript": "1.12.7-patch.2",
+    "decaffeinate-coffeescript2": "2.2.1-patch.1",
     "json-stable-stringify": "^1.0.1",
     "lines-and-columns": "^1.1.6"
   },

src/ext/coffee-script.ts

@@ -1,6 +1,9 @@
-import { Base, Op } from 'decaffeinate-coffeescript/lib/coffee-script/nodes';
+import { Base as CS1Base, Op as CS1Op } from 'decaffeinate-coffeescript/lib/coffee-script/nodes';
+import { Base, Op } from 'decaffeinate-coffeescript2/lib/coffeescript/nodes';
 
 export function patchCoffeeScript(): void {
+  CS1Op.prototype.invert = invert;
+  CS1Base.prototype.invert = invert;
   Op.prototype.invert = invert;
   Base.prototype.invert = invert;
 }

src/mappers/mapAny.ts

@@ -1,8 +1,8 @@
 import {
-  Arr, Assign, Base, Block, Call, Class, Code, Comment, Existence, Expansion, Extends,
-  For, If, In, Literal, ModuleDeclaration, Obj, Op, Param, Parens, Range, Return, Splat, Switch, TaggedTemplateCall,
-  Throw, Try, Value, While,
-} from 'decaffeinate-coffeescript/lib/coffee-script/nodes';
+  Arr, Assign, Base, Block, Call, Class, Code, Existence, Expansion, Extends, For, If, In, Literal, ModuleDeclaration,
+  Obj, Op, Param, Parens, Range, Return, Splat, StringWithInterpolations, Switch, TaggedTemplateCall, Throw, Try, Value,
+  While,
+} from 'decaffeinate-coffeescript2/lib/coffeescript/nodes';
 import { Node } from '../nodes';
 import ParseContext from '../util/ParseContext';
 import UnsupportedNodeError from '../util/UnsupportedNodeError';
@@ -79,7 +79,7 @@ export default function mapAny(context: ParseContext, node: Base): Node {
     return mapObj(context, node);
   }
 
-  if (node instanceof Parens) {
+  if (node instanceof Parens || node instanceof StringWithInterpolations) {
     return mapParens(context, node);
   }
 
@@ -143,10 +143,5 @@ export default function mapAny(context: ParseContext, node: Base): Node {
     return mapModuleDeclaration(context, node);
   }
 
-  if (node instanceof Comment) {
-    throw new UnsupportedNodeError(
-      node, 'Expected comment notes to be filtered out by mapBlock rather than processed directly.');
-  }
-
   throw new UnsupportedNodeError(node);
 }

src/mappers/mapArr.ts

@@ -1,4 +1,4 @@
-import { Arr } from 'decaffeinate-coffeescript/lib/coffee-script/nodes';
+import { Arr } from 'decaffeinate-coffeescript2/lib/coffeescript/nodes';
 import { ArrayInitialiser } from '../nodes';
 import getLocation from '../util/getLocation';
 import ParseContext from '../util/ParseContext';

src/mappers/mapAssign.ts

@@ -1,4 +1,4 @@
-import { Assign } from 'decaffeinate-coffeescript/lib/coffee-script/nodes';
+import { Assign } from 'decaffeinate-coffeescript2/lib/coffeescript/nodes';
 import { AssignOp, BaseAssignOp, BitAndOp, BitOrOp, BitXorOp, CompoundAssignOp, DivideOp, ExistsOp, ExpOp, FloorDivideOp, LeftShiftOp, LogicalAndOp, LogicalOrOp, ModuloOp, MultiplyOp, PlusOp, RemOp, SignedRightShiftOp, SubtractOp, UnsignedRightShiftOp } from '../nodes';
 import getLocation from '../util/getLocation';
 import ParseContext from '../util/ParseContext';

src/mappers/mapBlock.ts

@@ -1,8 +1,9 @@
 import { SourceType } from 'coffee-lex';
-import { Assign, Base, Block as CoffeeBlock, Comment, Obj, Value } from 'decaffeinate-coffeescript/lib/coffee-script/nodes';
+import { Assign, Base, Block as CoffeeBlock, Obj, Value } from 'decaffeinate-coffeescript2/lib/coffeescript/nodes';
 import { inspect } from 'util';
 import { AssignOp, Block, BoundFunction, BoundGeneratorFunction, ClassProtoAssignOp, Constructor, Identifier, MemberAccessOp, Node, This } from '../nodes';
 import getLocation from '../util/getLocation';
+import isCommentOnlyNode from '../util/isCommentOnlyNode';
 import ParseContext from '../util/ParseContext';
 import mapAny from './mapAny';
 
@@ -28,7 +29,7 @@ export default function mapBlock(context: ParseContext, node: CoffeeBlock): Bloc
   return new Block(
     line, column, start, end, raw,
     node.expressions
-      .filter(expression => !(expression instanceof Comment))
+      .filter(expression => !isCommentOnlyNode(expression))
       .map(expression => mapChild(context, childContext, expression))
       .reduce((arr, current) => arr.concat(current), []),
     inline
@@ -44,9 +45,7 @@ function mapChild(blockContext: ParseContext, childContext: ParseContext, node:
 
     let statements: Array<Node> = [];
     for (let property of obj.properties) {
-      if (property instanceof Comment) {
-        continue;
-      } else if (property instanceof Assign) {
+      if (property instanceof Assign) {
         let { line, column, start, end, raw } = getLocation(childContext, property);
         let key = mapAny(childContext, property.variable);
         let value = mapAny(childContext, property.value);

src/mappers/mapCall.ts

@@ -1,5 +1,12 @@
 import SourceType from 'coffee-lex/dist/SourceType';
-import { Call, Literal, Parens, Splat, SuperCall, Value } from 'decaffeinate-coffeescript/lib/coffee-script/nodes';
+import {
+  Call,
+  Literal,
+  Splat,
+  StringWithInterpolations,
+  SuperCall,
+  Value,
+} from 'decaffeinate-coffeescript2/lib/coffeescript/nodes';
 import { inspect } from 'util';
 import {
   AssignOp,
@@ -20,7 +27,7 @@ export default function mapCall(context: ParseContext, node: Call): Node {
 
   if (isHeregexTemplateNode(node, context)) {
     let firstArg = node.args[0];
-    if (!(firstArg instanceof Value) || !(firstArg.base instanceof Parens)) {
+    if (!(firstArg instanceof Value) || !(firstArg.base instanceof StringWithInterpolations)) {
       throw new Error('Expected a valid first heregex arg in the AST.');
     }
     let strNode = firstArg.base.body.expressions[0];

src/mappers/mapClass.ts

@@ -1,4 +1,4 @@
-import { Class as CoffeeClass } from 'decaffeinate-coffeescript/lib/coffee-script/nodes';
+import { Class as CoffeeClass } from 'decaffeinate-coffeescript2/lib/coffeescript/nodes';
 import { Class } from '../nodes';
 import getLocation from '../util/getLocation';
 import ParseContext from '../util/ParseContext';

src/mappers/mapCode.ts

@@ -1,4 +1,4 @@
-import { Code } from 'decaffeinate-coffeescript/lib/coffee-script/nodes';
+import { Code } from 'decaffeinate-coffeescript2/lib/coffeescript/nodes';
 import { BaseFunction, BoundFunction, BoundGeneratorFunction, Function, GeneratorFunction } from '../nodes';
 import getLocation from '../util/getLocation';
 import ParseContext from '../util/ParseContext';