1 files changed, 118 insertions, 0 deletions
diff --git a/llparse-builder/test/loop-checker-test.ts b/llparse-builder/test/loop-checker-test.ts
new file mode 100644
index 0000000..0df6064
--- /dev/null
+++ b/llparse-builder/test/loop-checker-test.ts
@@ -0,0 +1,118 @@
+import * as assert from 'assert';
+
+import { Builder, LoopChecker } from '../src/builder';
+
+describe('LLParse/LoopChecker', () => {
+  let b: Builder;
+  let lc: LoopChecker;
+  beforeEach(() => {
+    b = new Builder();
+    lc = new LoopChecker();
+  });
+
+  it('should detect shallow loops', () => {
+    const start = b.node('start');
+
+    start
+      .otherwise(start);
+
+    assert.throws(() => {
+      lc.check(start);
+    }, /Detected loop in "start".*"start"/);
+  });
+
+  it('should detect loops', () => {
+    const start = b.node('start');
+    const a = b.node('a');
+    const invoke = b.invoke(b.code.match('nop'), {
+      0: start,
+    }, b.error(1, 'error'));
+
+    start
+      .peek('a', a)
+      .otherwise(b.error(1, 'error'));
+
+    a.otherwise(invoke);
+
+    assert.throws(() => {
+      lc.check(start);
+    }, /Detected loop in "a".*"a" -> "invoke_nop"/);
+  });
+
+  it('should detect seemingly unreachable keys', () => {
+    const start = b.node('start');
+    const loop = b.node('loop');
+
+    start
+      .peek('a', loop)
+      .otherwise(b.error(1, 'error'));
+
+    loop
+      .match('a', loop)
+      .otherwise(loop);
+
+    assert.throws(() => {
+      lc.check(start);
+    }, /Detected loop in "loop" through.*"loop"/);
+  });
+
+  it('should ignore loops through `peek` to `match`', () => {
+    const start = b.node('start');
+    const a = b.node('a');
+    const invoke = b.invoke(b.code.match('nop'), {
+      0: start,
+    }, b.error(1, 'error'));
+
+    start
+      .peek('a', a)
+      .otherwise(b.error(1, 'error'));
+
+    a
+      .match('abc', invoke)
+      .otherwise(start);
+
+    assert.doesNotThrow(() => lc.check(start));
+  });
+
+  it('should ignore irrelevant `peek`s', () => {
+    const start = b.node('start');
+    const a = b.node('a');
+
+    start
+      .peek('a', a)
+      .otherwise(b.error(1, 'error'));
+
+    a
+      .peek('b', start)
+      .otherwise(b.error(1, 'error'));
+
+    assert.doesNotThrow(() => lc.check(start));
+  });
+
+  it('should ignore loops with multi `peek`/`match`', () => {
+    const start = b.node('start');
+    const another = b.node('another');
+
+    const NUM: ReadonlyArray<string> = [
+      '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
+    ];
+
+    const ALPHA: ReadonlyArray<string> = [
+      'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o',
+      'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
+      'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',
+      'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
+    ];
+
+    start
+      .match(ALPHA, start)
+      .peek(NUM, another)
+      .skipTo(start);
+
+    another
+      .match(NUM, another)
+      .otherwise(start);
+
+    assert.doesNotThrow(() => lc.check(start));
+  });
+});