pegjs/spec/compiler/passes/report-left-recursion.spec.js

describe("compiler pass |reportLeftRecursion|", function() {
  var pass = PEG.compiler.passes.reportLeftRecursion;

  beforeEach(function() {
    this.addMatchers({
      toReportLeftRecursionIn: function(grammar) {
        var ast = PEG.parser.parse(grammar);

        try {
          this.actual(ast);

          this.message = function() {
            return "Expected the pass to report left recursion for grammar "
                 + jasmine.pp(grammar) + ", "
                 + "but it didn't.";
          };

          return false;
        } catch (e) {
          if (this.isNot) {
            this.message = function() {
              return "Expected the pass not to report left recursion for grammar "
                   + jasmine.pp(grammar) + ", "
                   + "but it did.";
            };
          } else {
            this.message = function() {
              return "Expected the pass to report left recursion for grammar "
                   + jasmine.pp(grammar) + ", "
                   + "but it reported an error with message "
                   + jasmine.pp(e.message) + ".";
            };
          }

          return e.message === 'Left recursion detected for rule \"start\".';
        }
      }
    });
  });

  it("reports left recursion inside a rule", function() {
    expect(pass).toReportLeftRecursionIn('start = start');
  });

  it("reports left recursion inside a choice", function() {
    expect(pass).toReportLeftRecursionIn('start = start / "a" / "b"');
    expect(pass).toReportLeftRecursionIn('start = "a" / "b" / start');
  });

  it("reports left recursion inside a sequence", function() {
    expect(pass).toReportLeftRecursionIn('start = start "a" "b"');
  });

  it("reports left recursion inside a labeled", function() {
    expect(pass).toReportLeftRecursionIn('start = label:start');
  });

  it("reports left recursion inside a simple and", function() {
    expect(pass).toReportLeftRecursionIn('start = &start');
  });

  it("reports left recursion inside a simple not", function() {
    expect(pass).toReportLeftRecursionIn('start = &start');
  });

  it("reports left recursion inside an optional", function() {
    expect(pass).toReportLeftRecursionIn('start = start?');
  });

  it("reports left recursion inside a zero or more", function() {
    expect(pass).toReportLeftRecursionIn('start = start*');
  });

  it("reports left recursion inside a one or more", function() {
    expect(pass).toReportLeftRecursionIn('start = start+');
  });

  it("reports left recursion inside an action", function() {
    expect(pass).toReportLeftRecursionIn('start = start { }');
  });

  it("reports indirect left recursion", function() {
    expect(pass).toReportLeftRecursionIn([
      'start = stop',
      'stop  = start'
    ].join("\n"));
  });
});