Rewrite Hub as interface #5047

packages/babel-traverse/src/hub.js

@@ -1,5 +1,22 @@
-export default class Hub {
-  constructor(file) {
-    this.file = file;
+import type Scope from "./scope";
+
+export interface HubInterface {
+  getCode(): ?string;
+  getScope(): ?Scope;
+  addHelper(name: string): Object;
+  buildError(node: Object, msg: string, Error: Class<Error>): Error;
+}
+
+export default class Hub implements HubInterface {
+  getCode() {}
+
+  getScope() {}
+
+  addHelper() {
+    throw new Error("Helpers are not supported by the default hub.");
+  }
+
+  buildError(node, msg, Error = TypeError): Error {
+    return new Error(msg);
   }
 }

packages/babel-traverse/src/index.js

@@ -7,6 +7,7 @@ import * as cache from "./cache";
 export { default as NodePath } from "./path";
 export { default as Scope } from "./scope";
 export { default as Hub } from "./hub";
+export type { HubInterface } from "./hub";
 
 export { visitors };
 

packages/babel-traverse/src/path/conversion.js

@@ -133,7 +133,7 @@ export function arrowFunctionToExpression({
     this.get("body").unshiftContainer(
       "body",
       t.expressionStatement(
-        t.callExpression(this.hub.file.addHelper("newArrowCheck"), [
+        t.callExpression(this.hub.addHelper("newArrowCheck"), [
           t.thisExpression(),
           checkBinding
             ? t.identifier(checkBinding.name)

packages/babel-traverse/src/path/index.js

@@ -1,4 +1,4 @@
-import type Hub from "../hub";
+import type { HubInterface } from "../hub";
 import type TraversalContext from "../context";
 import * as virtualTypes from "./lib/virtual-types";
 import buildDebug from "debug";
@@ -24,7 +24,7 @@ import * as NodePath_comments from "./comments";
 const debug = buildDebug("babel");
 
 export default class NodePath {
-  constructor(hub: Hub, parent: Object) {
+  constructor(hub: HubInterface, parent: Object) {
     this.parent = parent;
     this.hub = hub;
     this.contexts = [];
@@ -49,7 +49,7 @@ export default class NodePath {
   }
 
   parent: Object;
-  hub: Hub;
+  hub: HubInterface;
   contexts: Array<TraversalContext>;
   data: Object;
   shouldSkip: boolean;
@@ -121,7 +121,7 @@ export default class NodePath {
   }
 
   buildCodeFrameError(msg: string, Error: typeof Error = SyntaxError): Error {
-    return this.hub.file.buildCodeFrameError(this.node, msg, Error);
+    return this.hub.buildError(this.node, msg, Error);
   }
 
   traverse(visitor: Object, state?: any) {

packages/babel-traverse/src/path/introspection.js

@@ -196,10 +196,10 @@ export function referencesImport(moduleSource, importName) {
 export function getSource() {
   const node = this.node;
   if (node.end) {
-    return this.hub.file.code.slice(node.start, node.end);
-  } else {
-    return "";
+    const code = this.hub.getCode();
+    if (code) return code.slice(node.start, node.end);
   }
+  return "";
 }
 
 export function willIMaybeExecuteBefore(target) {

packages/babel-traverse/src/scope/index.js

@@ -362,7 +362,7 @@ export default class Scope {
       (local.kind === "param" && (kind === "let" || kind === "const"));
 
     if (duplicate) {
-      throw this.hub.file.buildCodeFrameError(
+      throw this.hub.buildError(
         id,
         `Duplicate declaration "${name}"`,
         TypeError,
@@ -404,9 +404,7 @@ export default class Scope {
     console.log(sep);
   }
 
-  toArray(node: Object, i?: number | boolean) {
-    const file = this.hub.file;
-
+  toArray(node: Object, i?: number) {
     if (t.isIdentifier(node)) {
       const binding = this.getBinding(node.name);
       if (binding && binding.constant && binding.path.isGenericType("Array")) {
@@ -444,12 +442,12 @@ export default class Scope {
 
       // Used in array-rest to create an array from a subset of an iterable.
       helperName = "slicedToArray";
-      // TODO if (this.hub.file.isLoose("es6.forOf")) helperName += "-loose";
+      // TODO if (this.hub.isLoose("es6.forOf")) helperName += "-loose";
     } else {
       // Used in array-rest to create an array
       helperName = "toArray";
     }
-    return t.callExpression(file.addHelper(helperName), args);
+    return t.callExpression(this.hub.addHelper(helperName), args);
   }
 
   hasLabel(name: string) {