Allow callbacks to be specified for debug output

spec/runtime/document_spec.cc

@@ -1,4 +1,5 @@
 #include "runtime/runtime_spec_helper.h"
+#include "runtime/helpers/spy_debugger.h"
 
 extern "C" const TSLanguage * ts_language_json();
 
@@ -60,6 +61,73 @@ describe("Document", [&]() {
       });
     });
   });
+
+  describe("debugging", [&]() {
+    SpyDebugger *debugger;
+
+    before_each([&]() {
+      ts_document_set_language(doc, ts_language_json());
+      debugger = new SpyDebugger();
+    });
+
+    describe("debug_lex(TSDebugger)", [&]() {
+      before_each([&]() {
+        ts_document_debug_lex(doc, debugger->debugger());
+      });
+
+      it("calls the debugger with a message for each lex action", [&]() {
+        ts_document_set_input_string(doc, "[1, 2]");
+
+        AssertThat(debugger->messages, Contains("lookahead char:'1'"));
+        AssertThat(debugger->messages, Contains("accept_token sym:number"));
+        AssertThat(debugger->messages, Contains("advance state:1"));
+      });
+
+      describe("disabling debugging", [&]() {
+        before_each([&]() {
+          ts_document_debug_lex(doc, {});
+        });
+
+        it("does not call the debugger any more", [&]() {
+          ts_document_set_input_string(doc, "[1, 2]");
+          AssertThat(debugger->messages, IsEmpty());
+        });
+
+        it("releases the old debugger", [&]() {
+          AssertThat(debugger->release_call_count, Equals<size_t>(1));
+        });
+      });
+    });
+
+    describe("debug_parse(TSDebugger)", [&]() {
+      before_each([&]() {
+        ts_document_debug_parse(doc, debugger->debugger());
+      });
+
+      it("calls the debugger with a message for each parse action", [&]() {
+        ts_document_set_input_string(doc, "[1, 2]");
+
+        AssertThat(debugger->messages, Contains("lex sym:number"));
+        AssertThat(debugger->messages, Contains("shift state:1"));
+        AssertThat(debugger->messages, Contains("reduce sym:value count:1"));
+      });
+
+      describe("disabling debugging", [&]() {
+        before_each([&]() {
+          ts_document_debug_parse(doc, {});
+        });
+
+        it("does not call the debugger any more", [&]() {
+          ts_document_set_input_string(doc, "[1, 2]");
+          AssertThat(debugger->messages, IsEmpty());
+        });
+
+        it("releases the old debugger", [&]() {
+          AssertThat(debugger->release_call_count, Equals<size_t>(1));
+        });
+      });
+    });
+  });
 });
 
 END_TEST

spec/runtime/helpers/spy_debugger.cc

@@ -0,0 +1,28 @@
+#include "runtime/helpers/spy_debugger.h"
+#include <string>
+#include <vector>
+
+using std::string;
+using std::vector;
+
+static void spy_debug(void *data, const char *msg) {
+  SpyDebugger *debugger = static_cast<SpyDebugger *>(data);
+  debugger->messages.push_back(msg);
+}
+
+static void spy_release(void *data) {
+  SpyDebugger *debugger = static_cast<SpyDebugger *>(data);
+  debugger->release_call_count++;
+}
+
+TSDebugger SpyDebugger::debugger() {
+  TSDebugger result;
+  result.data = (void *)this;
+  result.debug_fn = spy_debug;
+  result.release_fn = spy_release;
+  return result;
+}
+
+void SpyDebugger::clear() {
+  messages.clear();
+}

spec/runtime/helpers/spy_debugger.h

@@ -0,0 +1,18 @@
+#ifndef HELPERS_SPY_DEBUGGER_H_
+#define HELPERS_SPY_DEBUGGER_H_
+
+#include <string>
+#include <vector>
+#include "tree_sitter/runtime.h"
+
+class SpyDebugger {
+ public:
+  void clear();
+  TSDebugger debugger();
+
+  std::vector<std::string> messages;
+  size_t release_call_count;
+};
+
+#endif  // HELPERS_SPY_DEBUGGER_H_
+