4 files changed, 48 insertions, 22 deletions

diff --git a/absl/strings/internal/str_format/arg_test.cc b/absl/strings/internal/str_format/arg_test.cc
index 04fa56cd3623..8d30d8b8ce34 100644
--- a/absl/strings/internal/str_format/arg_test.cc
+++ b/absl/strings/internal/str_format/arg_test.cc
@@ -96,10 +96,10 @@ TEST_F(FormatArgImplTest, WorksWithCharArraysOfUnknownSize) {
   std::string s;
   FormatSinkImpl sink(&s);
   ConversionSpec conv;
-  conv.set_conv(ConversionChar::s);
-  conv.set_flags(Flags());
-  conv.set_width(-1);
-  conv.set_precision(-1);
+  FormatConversionSpecImplFriend::SetConversionChar(ConversionChar::s, &conv);
+  FormatConversionSpecImplFriend::SetFlags(Flags(), &conv);
+  FormatConversionSpecImplFriend::SetWidth(-1, &conv);
+  FormatConversionSpecImplFriend::SetPrecision(-1, &conv);
   EXPECT_TRUE(
       FormatArgImplFriend::Convert(FormatArgImpl(kMyArray), conv, &sink));
   sink.Flush();
diff --git a/absl/strings/internal/str_format/bind.cc b/absl/strings/internal/str_format/bind.cc
index 2d19b613e43d..27522fdb4f62 100644
--- a/absl/strings/internal/str_format/bind.cc
+++ b/absl/strings/internal/str_format/bind.cc
@@ -66,18 +66,22 @@ inline bool ArgContext::Bind(const UnboundConversion* unbound,
         return false;
     }
 
-    bound->set_width(width);
-    bound->set_precision(precision);
-    bound->set_flags(unbound->flags);
-    if (force_left)
-      bound->set_left(true);
+    FormatConversionSpecImplFriend::SetWidth(width, bound);
+    FormatConversionSpecImplFriend::SetPrecision(precision, bound);
+
+    if (force_left) {
+      Flags flags = unbound->flags;
+      flags.left = true;
+      FormatConversionSpecImplFriend::SetFlags(flags, bound);
+    } else {
+      FormatConversionSpecImplFriend::SetFlags(unbound->flags, bound);
+    }
   } else {
-    bound->set_flags(unbound->flags);
-    bound->set_width(-1);
-    bound->set_precision(-1);
+    FormatConversionSpecImplFriend::SetFlags(unbound->flags, bound);
+    FormatConversionSpecImplFriend::SetWidth(-1, bound);
+    FormatConversionSpecImplFriend::SetPrecision(-1, bound);
   }
-
-  bound->set_conv(unbound->conv);
+  FormatConversionSpecImplFriend::SetConversionChar(unbound->conv, bound);
   bound->set_arg(arg);
   return true;
 }
@@ -139,7 +143,8 @@ class SummarizingConverter {
     UntypedFormatSpecImpl spec("%d");
 
     std::ostringstream ss;
-    ss << "{" << Streamable(spec, {*bound.arg()}) << ":" << bound.flags();
+    ss << "{" << Streamable(spec, {*bound.arg()}) << ":"
+       << FormatConversionSpecImplFriend::FlagsToString(bound);
     if (bound.width() >= 0) ss << bound.width();
     if (bound.precision() >= 0) ss << "." << bound.precision();
     ss << bound.conv() << "}";
diff --git a/absl/strings/internal/str_format/extension.h b/absl/strings/internal/str_format/extension.h
index 1a863c207bb1..16f6c0a4b205 100644
--- a/absl/strings/internal/str_format/extension.h
+++ b/absl/strings/internal/str_format/extension.h
@@ -260,9 +260,21 @@ inline std::ostream& operator<<(std::ostream& os, FormatConversionChar v) {
   return os << c;
 }
 
+struct FormatConversionSpecImplFriend;
+
 class ConversionSpec {
  public:
+  // Deprecated (use has_x_flag() instead).
   Flags flags() const { return flags_; }
+
+  // Width and precison are not specified, no flags are set.
+  bool is_basic() const { return flags_.basic; }
+  bool has_left_flag() const { return flags_.left; }
+  bool has_show_pos_flag() const { return flags_.show_pos; }
+  bool has_sign_col_flag() const { return flags_.sign_col; }
+  bool has_alt_flag() const { return flags_.alt; }
+  bool has_zero_flag() const { return flags_.zero; }
+
   FormatConversionChar conv() const {
     // Keep this field first in the struct . It generates better code when
     // accessing it when ConversionSpec is passed by value in registers.
@@ -277,19 +289,28 @@ class ConversionSpec {
   // negative value.
   int precision() const { return precision_; }
 
-  void set_flags(Flags f) { flags_ = f; }
-  void set_conv(FormatConversionChar c) { conv_ = c; }
-  void set_width(int w) { width_ = w; }
-  void set_precision(int p) { precision_ = p; }
-  void set_left(bool b) { flags_.left = b; }
-
  private:
+  friend struct str_format_internal::FormatConversionSpecImplFriend;
   FormatConversionChar conv_ = FormatConversionChar::kNone;
   Flags flags_;
   int width_;
   int precision_;
 };
 
+struct FormatConversionSpecImplFriend final {
+  static void SetFlags(Flags f, ConversionSpec* conv) { conv->flags_ = f; }
+  static void SetConversionChar(FormatConversionChar c, ConversionSpec* conv) {
+    conv->conv_ = c;
+  }
+  static void SetWidth(int w, ConversionSpec* conv) { conv->width_ = w; }
+  static void SetPrecision(int p, ConversionSpec* conv) {
+    conv->precision_ = p;
+  }
+  static std::string FlagsToString(const ConversionSpec& spec) {
+    return spec.flags_.ToString();
+  }
+};
+
 constexpr uint64_t FormatConversionCharToConvValue(char conv) {
   return
 #define CONV_SET_CASE(c)                                                     \
diff --git a/absl/strings/internal/str_format/float_conversion.cc b/absl/strings/internal/str_format/float_conversion.cc
index c98ed4ba5008..d4c647c3ed99 100644
--- a/absl/strings/internal/str_format/float_conversion.cc
+++ b/absl/strings/internal/str_format/float_conversion.cc
@@ -28,7 +28,7 @@ bool FallbackToSnprintf(const Float v, const ConversionSpec &conv,
   {
     char *fp = fmt;
     *fp++ = '%';
-    fp = CopyStringTo(conv.flags().ToString(), fp);
+    fp = CopyStringTo(FormatConversionSpecImplFriend::FlagsToString(conv), fp);
     fp = CopyStringTo("*.*", fp);
     if (std::is_same<long double, Float>()) {
       *fp++ = 'L';