From 6d2d8f5c1913278035e41ede7ca313f1fd09aa6e Mon Sep 17 00:00:00 2001
From: Glen Van Ginkel <glen.vanginkel@nanoporetech.com>
Date: Sat, 10 Oct 2020 14:48:37 +0100
Subject: [PATCH] Support root character

---
 src/Lexer.ts           |  2 ++
 src/Parser.ts          |  3 +++
 src/TreeInterpreter.ts |  4 ++++
 test/jmespath.spec.js  | 22 ++++++++++++++++++++++
 4 files changed, 31 insertions(+)

diff --git a/src/Lexer.ts b/src/Lexer.ts
index bbfd13b..0367481 100644
--- a/src/Lexer.ts
+++ b/src/Lexer.ts
@@ -12,6 +12,7 @@ export enum Token {
   TOK_RBRACE = 'Rbrace',
   TOK_NUMBER = 'Number',
   TOK_CURRENT = 'Current',
+  TOK_ROOT = 'Root',
   TOK_EXPREF = 'Expref',
   TOK_PIPE = 'Pipe',
   TOK_OR = 'Or',
@@ -74,6 +75,7 @@ export const basicTokens = {
   '.': Token.TOK_DOT,
   ':': Token.TOK_COLON,
   '@': Token.TOK_CURRENT,
+  ['$']: Token.TOK_ROOT,
   ']': Token.TOK_RBRACKET,
   '{': Token.TOK_LBRACE,
   '}': Token.TOK_RBRACE,
diff --git a/src/Parser.ts b/src/Parser.ts
index ec295e3..cce8a8a 100644
--- a/src/Parser.ts
+++ b/src/Parser.ts
@@ -22,6 +22,7 @@ const bindingPower: { [token: string]: number } = {
   [Token.TOK_NUMBER]: 0,
   [Token.TOK_CURRENT]: 0,
   [Token.TOK_EXPREF]: 0,
+  [Token.TOK_ROOT]: 0,
   [Token.TOK_PIPE]: 1,
   [Token.TOK_OR]: 2,
   [Token.TOK_AND]: 3,
@@ -134,6 +135,8 @@ class TokenParser {
         return this.parseMultiselectList();
       case Token.TOK_CURRENT:
         return { type: Token.TOK_CURRENT };
+      case Token.TOK_ROOT:
+        return { type: Token.TOK_ROOT };
       case Token.TOK_EXPREF:
         expression = this.expression(bindingPower.Expref);
         return { type: 'ExpressionReference', children: [expression] } as ExpressionNode;
diff --git a/src/TreeInterpreter.ts b/src/TreeInterpreter.ts
index a295067..522fbf5 100644
--- a/src/TreeInterpreter.ts
+++ b/src/TreeInterpreter.ts
@@ -13,12 +13,14 @@ import { JSONValue } from '.';
 
 export class TreeInterpreter {
   runtime: Runtime;
+  private _rootValue: JSONValue | null = null;
 
   constructor() {
     this.runtime = new Runtime(this);
   }
 
   search(node: ExpressionNodeTree, value: JSONValue): JSONValue {
+    this._rootValue = value;
     return this.visit(node, value) as JSONValue;
   }
 
@@ -224,6 +226,8 @@ export class TreeInterpreter {
         return this.visit((node as ExpressionNode).children[1], left);
       case Token.TOK_CURRENT:
         return value;
+      case Token.TOK_ROOT:
+        return this._rootValue;
       case 'Function':
         const resolvedArgs: JSONValue[] = [];
         for (let j = 0; j < (node as ExpressionNode).children.length; j += 1) {
diff --git a/test/jmespath.spec.js b/test/jmespath.spec.js
index e3310ef..6b8690b 100644
--- a/test/jmespath.spec.js
+++ b/test/jmespath.spec.js
@@ -349,3 +349,25 @@ describe('registerFunction', () => {
     ).toThrow('ArgumentError: optionalArgs() takes 1 arguments but received 3');
   });
 });
+
+describe('root', () => {
+  it('$ should give access to the root value', () => {
+    var value = search({ foo: { bar: 1 } }, 'foo.{ value: $.foo.bar }');
+    expect(value.value).toBe(1);
+  });
+  it('$ should give access to the root value after pipe', () => {
+    var value = search({ foo: { bar: 1 } }, 'foo | $.foo.bar');
+    expect(value).toEqual(1);
+  });
+  it('$ should give access in expressions', () => {
+    var value = search([{ foo: { bar: 1 } }, { foo: { bar: 99 } }], 'map(&foo.{boo: bar, root: $}, @)');
+    expect(value).toEqual([
+      { boo: 1, root: [{ foo: { bar: 1 } }, { foo: { bar: 99 } }] },
+      { boo: 99, root: [{ foo: { bar: 1 } }, { foo: { bar: 99 } }] },
+    ]);
+  });
+  it('$ can be used in parallel', () => {
+    var value = search([{ foo: { bar: 1 } }, { foo: { bar: 99 } }], '[$[0].foo.bar, $[1].foo.bar]');
+    expect(value).toEqual([1, 99]);
+  });
+});