pegjs/spec/api/generated-parser-api.spec.js

describe("generated parser API", function() {
  describe("parse", function() {
    it("parses input", function() {
      var parser = PEG.buildParser('start = "a"');

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

    it("throws an exception on syntax error", function() {
      var parser = PEG.buildParser('start = "a"');

      expect(function() { parser.parse("b"); }).toThrow();
    });

    describe("start rule", function() {
      var parser = PEG.buildParser([
            'a = "x" { return "a"; }',
            'b = "x" { return "b"; }',
            'c = "x" { return "c"; }'
          ].join("\n"), { allowedStartRules: ["b", "c"] });

      describe("when |startRule| is not set", function() {
        it("starts parsing from the first allowed rule", function() {
          expect(parser.parse("x")).toBe("b");
        });
      });

      describe("when |startRule| is set to an allowed rule", function() {
        it("starts parsing from specified rule", function() {
          expect(parser.parse("x", { startRule: "b" })).toBe("b");
          expect(parser.parse("x", { startRule: "c" })).toBe("c");
        });
      });

      describe("when |startRule| is set to a disallowed start rule", function() {
        it("throws an exception", function() {
          expect(
            function() { parser.parse("x", { startRule: "a" }); }
          ).toThrow();
        });
      });
    });

    describe("tracing", function() {
      var parser = PEG.buildParser([
            'start = a / b',
            'a = "a"',
            'b = "b"'
          ].join("\n"), { trace: true });

      describe("default tracer", function() {
        it("traces using console.log", function() {
          spyOn(console, "log");

          parser.parse("b");

          expect(console.log).toHaveBeenCalledWith("1:1 rule.enter start");
          expect(console.log).toHaveBeenCalledWith("1:1 rule.enter   a");
          expect(console.log).toHaveBeenCalledWith("1:1 rule.fail    a");
          expect(console.log).toHaveBeenCalledWith("1:1 rule.enter   b");
          expect(console.log).toHaveBeenCalledWith("1:2 rule.match   b");
          expect(console.log).toHaveBeenCalledWith("1:2 rule.match start");
        });
      });

      describe("custom tracers", function() {
        describe("trace", function() {
          it("receives tracing events", function() {
            var tracer = { trace: function() { } };

            spyOn(tracer, "trace");

            parser.parse("b", { tracer: tracer });

            expect(tracer.trace).toHaveBeenCalledWith({
              type:   'rule.enter',
              rule:   'start',
              offset: 0,
              line:   1,
              column: 1
            });
            expect(tracer.trace).toHaveBeenCalledWith({
              type:   'rule.enter',
              rule:   'a',
              offset: 0,
              line:   1,
              column: 1
            });
            expect(tracer.trace).toHaveBeenCalledWith({
              type:   'rule.fail',
              rule:   'a',
              offset: 0,
              line:   1,
              column: 1
            });
            expect(tracer.trace).toHaveBeenCalledWith({
              type:   'rule.enter',
              rule:   'b',
              offset: 0,
              line:   1,
              column: 1
            });
            expect(tracer.trace).toHaveBeenCalledWith({
              type:   'rule.match',
              rule:   'b',
              result: 'b',
              offset: 1,
              line:   1,
              column: 2
            });
            expect(tracer.trace).toHaveBeenCalledWith({
              type:   'rule.match',
              rule:   'start',
              result: 'b',
              offset: 1,
              line:   1,
              column: 2
            });
          });
        });
      });
    });

    it("accepts custom options", function() {
      var parser = PEG.buildParser('start = "a"');

      parser.parse("a", { foo: 42 });
    });
  });
});