Start work on randomized changed-region testing

Signed-off-by: Nathan Sobo <nathan@github.com>

spec/helpers/scope_sequence.cc

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+#include "./scope_sequence.h"
+
+#include "bandit/bandit.h"
+#include <sstream>
+#include "helpers/stream_methods.h"
+#include "helpers/point_helpers.h"
+
+using std::string;
+using std::cout;
+
+static void append_text_to_scope_sequence(ScopeSequence *sequence,
+                                          ScopeStack *current_scopes,
+                                          const std::string &text,
+                                          size_t length) {
+  for (size_t i = 0; i < length; i++) {
+    string character(1, text[sequence->size()]);
+    sequence->push_back(*current_scopes);
+    sequence->back().push_back("'" + character + "'");
+  }
+}
+
+static void append_to_scope_sequence(ScopeSequence *sequence,
+                                     ScopeStack *current_scopes,
+                                     TSNode node, TSDocument *document,
+                                     const std::string &text) {
+  string scope = ts_node_type(node, document);
+  current_scopes->push_back(scope);
+  size_t child_count = ts_node_child_count(node);
+  if (child_count > 0) {
+    size_t previous_child_end = ts_node_start_char(node);
+    for (size_t i = 0; i < child_count; i++) {
+      TSNode child = ts_node_child(node, i);
+      size_t child_start = ts_node_start_char(child);
+      size_t spacing = child_start - previous_child_end;
+      append_text_to_scope_sequence(sequence, current_scopes, text, spacing);
+      append_to_scope_sequence(sequence, current_scopes, child, document, text);
+      previous_child_end = ts_node_end_char(child);
+    }
+    size_t spacing = ts_node_end_char(node) - previous_child_end;
+    append_text_to_scope_sequence(sequence, current_scopes, text, spacing);
+  } else {
+    size_t length = ts_node_end_char(node) - ts_node_start_char(node);
+    append_text_to_scope_sequence(sequence, current_scopes, text, length);
+  }
+  current_scopes->pop_back();
+}
+
+ScopeSequence build_scope_sequence(TSDocument *document, const std::string &text) {
+  ScopeSequence sequence;
+  ScopeStack current_scopes;
+  TSNode node = ts_document_root_node(document);
+  append_to_scope_sequence(&sequence, &current_scopes, node, document, text);
+  AssertThat(sequence.size(), Equals(text.size()));
+  return sequence;
+}
+
+bool operator<=(const TSPoint &left, const TSPoint &right) {
+  if (left.row < right.row)
+    return true;
+  else if (left.row == right.row)
+    return left.column <= right.column;
+  else
+    return false;
+}
+
+void verify_changed_ranges(const ScopeSequence &old_sequence, const ScopeSequence &new_sequence,
+                           const string &text, TSRange *ranges, size_t range_count) {
+  TSPoint current_position = {0, 0};
+  for (size_t i = 0; i < text.size(); i++) {
+    if (text[i] == '\n') {
+      current_position.row++;
+      current_position.column = 0;
+      continue;
+    }
+
+    const ScopeStack &old_scopes = old_sequence[i];
+    const ScopeStack &new_scopes = new_sequence[i];
+    if (old_scopes != new_scopes) {
+      bool found_containing_range = false;
+      for (size_t j = 0; j < range_count; j++) {
+        TSRange range = ranges[j];
+        if (range.start <= current_position && current_position <= range.end) {
+          found_containing_range = true;
+          break;
+        }
+      }
+
+      if (!found_containing_range) {
+        std::stringstream message_stream;
+        message_stream << "Found changed scope outside of any invalidated range;\n";
+        message_stream << "Position: " << current_position << "\n";
+        size_t line_start_index = i - current_position.column;
+        size_t line_end_index = text.find_first_of('\n', i);
+        message_stream << "Line: " << text.substr(line_start_index, line_end_index - line_start_index) << "\n";
+        for (size_t j = 0; j < current_position.column + string("Line: ").size(); j++)
+          message_stream << " ";
+        message_stream << "^\n";
+        message_stream << "Old scopes: " << old_scopes << "\n";
+        message_stream << "New scopes: " << new_scopes << "\n";
+        message_stream << "Invalidated ranges:\n";
+        for (size_t j = 0; j < range_count; j++) {
+          message_stream << "  " << ranges[i] << "\n";
+        }
+        Assert::Failure(message_stream.str());
+      }
+    }
+
+    current_position.column++;
+  }
+}

spec/helpers/scope_sequence.h

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+#ifndef HELPERS_SCOPE_SEQUENCE_H_
+#define HELPERS_SCOPE_SEQUENCE_H_
+
+#include <string>
+#include <vector>
+#include "tree_sitter/runtime.h"
+
+typedef std::string Scope;
+typedef std::vector<Scope> ScopeStack;
+typedef std::vector<ScopeStack> ScopeSequence;
+
+ScopeSequence build_scope_sequence(TSDocument *document, const std::string &text);
+
+void verify_changed_ranges(const ScopeSequence &old, const ScopeSequence &new_sequence, const std::string &text, TSRange *ranges, size_t range_count);
+
+#endif  // HELPERS_SCOPE_SEQUENCE_H_