pegjs/spec/api/plugin-api.spec.js

"use strict";

let peg = require("../../lib/peg");

describe("plugin API", function() {
  beforeEach(function() {
    this.addMatchers({
      toBeObject: function() {
        this.message = () =>
          "Expected " + jasmine.pp(this.actual) + " "
            + (this.isNot ? "not " : "")
            + "to be an object.";

        return this.actual !== null && typeof this.actual === "object";
      },

      toBeArray: function() {
        this.message = () =>
          "Expected " + jasmine.pp(this.actual) + " "
            + (this.isNot ? "not " : "")
            + "to be an array.";

        return Object.prototype.toString.apply(this.actual) === "[object Array]";
      },

      toBeFunction: function() {
        this.message = () =>
          "Expected " + jasmine.pp(this.actual) + " "
            + (this.isNot ? "not " : "")
            + "to be a function.";

        return typeof this.actual === "function";
      }
    });
  });

  describe("use", function() {
    let grammar = "start = 'a'";

    it("is called for each plugin", function() {
      let pluginsUsed = [false, false, false];
      let plugins     = [
            { use: function() { pluginsUsed[0] = true; } },
            { use: function() { pluginsUsed[1] = true; } },
            { use: function() { pluginsUsed[2] = true; } }
          ];

      peg.generate(grammar, { plugins: plugins });

      expect(pluginsUsed).toEqual([true, true, true]);
    });

    it("receives configuration", function() {
      let plugin = {
            use: function(config) {
              expect(config).toBeObject();

              expect(config.parser).toBeObject();
              expect(config.parser.parse("start = 'a'")).toBeObject();

              expect(config.passes).toBeObject();

              expect(config.passes.check).toBeArray();
              config.passes.check.forEach(pass => {
                expect(pass).toBeFunction();
              });

              expect(config.passes.transform).toBeArray();
              config.passes.transform.forEach(pass => {
                expect(pass).toBeFunction();
              });

              expect(config.passes.generate).toBeArray();
              config.passes.generate.forEach(pass => {
                expect(pass).toBeFunction();
              });
            }
          };

      peg.generate(grammar, { plugins: [plugin] });
    });

    it("receives options", function() {
      let plugin             = {
            use: function(config, options) {
              expect(options).toEqual(generateOptions);
            }
          };
      let generateOptions = { plugins: [plugin], foo: 42 };

      peg.generate(grammar, generateOptions);
    });

    it("can replace parser", function() {
      let plugin = {
            use: function(config) {
              let parser = peg.generate([
                    "start = .* {",
                    "  return {",
                    "    type:  'grammar',",
                    "    rules: [",
                    "      {",
                    "        type:       'rule',",
                    "        name:       'start',",
                    "        expression: { type: 'literal',  value: text(), ignoreCase: false }",
                    "      }",
                    "    ]",
                    "  };",
                    "}"
                  ].join("\n"));

              config.parser = parser;
            }
          };
      let parser = peg.generate("a", { plugins: [plugin] });

      expect(parser.parse("a")).toBe("a");
    });

    it("can change compiler passes", function() {
      let plugin = {
            use: function(config) {
              let pass = ast => {
                    ast.code = "({ parse: function() { return 42; } })";
                  };

              config.passes.generate = [pass];
            }
          };
      let parser = peg.generate(grammar, { plugins: [plugin] });

      expect(parser.parse("a")).toBe(42);
    });

    it("can change options", function() {
      let grammar = [
            "a = 'x'",
            "b = 'x'",
            "c = 'x'"
          ].join("\n");
      let plugin  = {
            use: function(config, options) {
              options.allowedStartRules = ["b", "c"];
            }
          };
      let parser  = peg.generate(grammar, {
            allowedStartRules: ["a"],
            plugins:           [plugin]
          });

      expect(() => { parser.parse("x", { startRule: "a" }); }).toThrow();
      expect(parser.parse("x", { startRule: "b" })).toBe("x");
      expect(parser.parse("x", { startRule: "c" })).toBe("x");
    });
  });
});