Implements custom description string for MATCHER*.

src/gmock-matchers.cc

@@ -31,10 +31,15 @@
 
 // Google Mock - a framework for writing C++ mock classes.
 //
-// This file implements the Matcher<const string&> and
-// Matcher<string>.
+// This file implements Matcher<const string&>, Matcher<string>, and
+// utilities for defining matchers.
 
 #include <gmock/gmock-matchers.h>
+#include <gmock/gmock-generated-matchers.h>
+
+#include <string.h>
+#include <sstream>
+#include <string>
 
 namespace testing {
 
@@ -58,4 +63,140 @@ Matcher<internal::string>::Matcher(const char* s) {
   *this = Eq(internal::string(s));
 }
 
+namespace internal {
+
+// Utilities for validating and formatting description strings in the
+// MATCHER*() macros.
+
+// Returns the 0-based index of the given parameter in the
+// NULL-terminated parameter array; if the parameter is "*", returns
+// kTupleInterpolation; if it's not found in the list, returns
+// kInvalidInterpolation.
+int GetParamIndex(const char* param_names[], const string& param_name) {
+  if (param_name == "*")
+    return kTupleInterpolation;
+
+  for (int i = 0; param_names[i] != NULL; i++) {
+    if (param_name == param_names[i])
+      return i;
+  }
+  return kInvalidInterpolation;
+}
+
+// If *pstr starts with the given prefix, modifies *pstr to be right
+// past the prefix and returns true; otherwise leaves *pstr unchanged
+// and returns false.  None of pstr, *pstr, and prefix can be NULL.
+bool SkipPrefix(const char* prefix, const char** pstr) {
+  const size_t prefix_len = strlen(prefix);
+  if (strncmp(*pstr, prefix, prefix_len) == 0) {
+    *pstr += prefix_len;
+    return true;
+  }
+  return false;
+}
+
+// Helper function used by ValidateMatcherDescription() to format
+// error messages.
+string FormatMatcherDescriptionSyntaxError(const char* description,
+                                           const char* error_pos) {
+  ::std::stringstream ss;
+  ss << "Syntax error at index " << (error_pos - description)
+     << " in matcher description \"" << description << "\": ";
+  return ss.str();
+}
+
+// Parses a matcher description string and returns a vector of
+// interpolations that appear in the string; generates non-fatal
+// failures iff 'description' is an invalid matcher description.
+// 'param_names' is a NULL-terminated array of parameter names in the
+// order they appear in the MATCHER_P*() parameter list.
+Interpolations ValidateMatcherDescription(
+    const char* param_names[], const char* description) {
+  Interpolations interps;
+  for (const char* p = description; *p != '\0';) {
+    if (SkipPrefix("%%", &p)) {
+      interps.push_back(Interpolation(p - 2, p, kPercentInterpolation));
+    } else if (SkipPrefix("%(", &p)) {
+      const char* const q = strstr(p, ")s");
+      if (q == NULL) {
+        // TODO(wan@google.com): change the source file location in
+        // the failure to point to where the MATCHER*() macro is used.
+        ADD_FAILURE() << FormatMatcherDescriptionSyntaxError(description, p - 2)
+                      << "an interpolation must end with \")s\", "
+                      << "but \"" << (p - 2) << "\" does not.";
+      } else {
+        const string param_name(p, q);
+        const int param_index = GetParamIndex(param_names, param_name);
+        if (param_index == kInvalidInterpolation) {
+          ADD_FAILURE() << FormatMatcherDescriptionSyntaxError(description, p)
+                        << "\"" << param_name
+                        << "\" is an invalid parameter name.";
+        } else {
+          interps.push_back(Interpolation(p - 2, q + 2, param_index));
+          p = q + 2;
+        }
+      }
+    } else {
+      EXPECT_NE(*p, '%') << FormatMatcherDescriptionSyntaxError(description, p)
+                         << "use \"%%\" instead of \"%\" to print \"%\".";
+      ++p;
+    }
+  }
+  return interps;
+}
+
+// Joins a vector of strings as if they are fields of a tuple; returns
+// the joined string.
+string JoinAsTuple(const Strings& fields) {
+  switch (fields.size()) {
+    case 0:
+      return "";
+    case 1:
+      return fields[0];
+    default:
+      string result = "(" + fields[0];
+      for (size_t i = 1; i < fields.size(); i++) {
+        result += ", ";
+        result += fields[i];
+      }
+      result += ")";
+      return result;
+  }
+}
+
+// Returns the actual matcher description, given the matcher name,
+// user-supplied description template string, interpolations in the
+// string, and the printed values of the matcher parameters.
+string FormatMatcherDescription(
+    const char* matcher_name, const char* description,
+    const Interpolations& interp, const Strings& param_values) {
+  string result;
+  if (*description == '\0') {
+    // When the user supplies an empty description, we calculate one
+    // from the matcher name.
+    result = ConvertIdentifierNameToWords(matcher_name);
+    if (param_values.size() >= 1)
+      result += " " + JoinAsTuple(param_values);
+  } else {
+    // The end position of the last interpolation.
+    const char* last_interp_end = description;
+    for (size_t i = 0; i < interp.size(); i++) {
+      result.append(last_interp_end, interp[i].start_pos);
+      const int param_index = interp[i].param_index;
+      if (param_index == kTupleInterpolation) {
+        result += JoinAsTuple(param_values);
+      } else if (param_index == kPercentInterpolation) {
+        result += '%';
+      } else if (param_index != kInvalidInterpolation) {
+        result += param_values[param_index];
+      }
+      last_interp_end = interp[i].end_pos;
+    }
+    result += last_interp_end;
+  }
+
+  return result;
+}
+
+}  // namespace internal
 }  // namespace testing