[clang-format] Add an option to format numeric literal case (#151590)

Some languages have the flexibility to use upper or lower case
characters interchangeably in integer and float literal definitions.

I'd like to be able to enforce a consistent case style in one of my
projects, so I added this clang-format style option to control it.

With this .clang-format configuration:
```yaml
    NumericLiteralCaseStyle:
      UpperCasePrefix: Never
      UpperCaseHexDigit: Always
      UpperCaseSuffix: Never
```

This line of code:
```C
    unsigned long long  0XdEaDbEeFUll;
```

gets reformatted into this line of code:
```C
    unsigned long long 0xDEAFBEEFull;
```

-----

I'm new to this project, so please let me know if I missed something in
the process. I modeled this PR from
[IntegerLiteralSeparatorFixer](https://reviews.llvm.org/D140543)

Author: 30Wedge

clang/docs/ClangFormatStyleOptions.rst

@@ -5079,6 +5079,113 @@ the configuration (without a prefix: ``Auto``).
 
   For example: TESTSUITE
 
+.. _NumericLiteralCase:
+
+**NumericLiteralCase** (``NumericLiteralCaseStyle``) :versionbadge:`clang-format 22` :ref:`¶ <NumericLiteralCase>`
+  Capitalization style for numeric literals.
+
+  Nested configuration flags:
+
+  Separate control for each numeric literal component.
+
+  For example, the config below will leave exponent letters alone, reformat
+  hexadecimal digits in lowercase, reformat numeric literal prefixes in
+  uppercase, and reformat suffixes in lowercase.
+
+  .. code-block:: c++
+
+    NumericLiteralCase:
+      ExponentLetter: Leave
+      HexDigit: Lower
+      Prefix: Upper
+      Suffix: Lower
+
+  * ``NumericLiteralComponentStyle ExponentLetter``
+    Format floating point exponent separator letter case.
+
+    .. code-block:: c++
+
+      float a = 6.02e23 + 1.0E10; // Leave
+      float a = 6.02E23 + 1.0E10; // Upper
+      float a = 6.02e23 + 1.0e10; // Lower
+
+    Possible values:
+
+    * ``NLCS_Leave`` (in configuration: ``Leave``)
+      Leave this component of the literal as is.
+
+    * ``NLCS_Upper`` (in configuration: ``Upper``)
+      Format this component with uppercase characters.
+
+    * ``NLCS_Lower`` (in configuration: ``Lower``)
+      Format this component with lowercase characters.
+
+
+  * ``NumericLiteralComponentStyle HexDigit``
+    Format hexadecimal digit case.
+
+    .. code-block:: c++
+
+      a = 0xaBcDeF; // Leave
+      a = 0xABCDEF; // Upper
+      a = 0xabcdef; // Lower
+
+    Possible values:
+
+    * ``NLCS_Leave`` (in configuration: ``Leave``)
+      Leave this component of the literal as is.
+
+    * ``NLCS_Upper`` (in configuration: ``Upper``)
+      Format this component with uppercase characters.
+
+    * ``NLCS_Lower`` (in configuration: ``Lower``)
+      Format this component with lowercase characters.
+
+
+  * ``NumericLiteralComponentStyle Prefix``
+    Format integer prefix case.
+
+    .. code-block:: c++
+
+       a = 0XF0 | 0b1; // Leave
+       a = 0XF0 | 0B1; // Upper
+       a = 0xF0 | 0b1; // Lower
+
+    Possible values:
+
+    * ``NLCS_Leave`` (in configuration: ``Leave``)
+      Leave this component of the literal as is.
+
+    * ``NLCS_Upper`` (in configuration: ``Upper``)
+      Format this component with uppercase characters.
+
+    * ``NLCS_Lower`` (in configuration: ``Lower``)
+      Format this component with lowercase characters.
+
+
+  * ``NumericLiteralComponentStyle Suffix``
+    Format suffix case. This option excludes case-sensitive reserved
+    suffixes, such as ``min`` in C++.
+
+    .. code-block:: c++
+
+      a = 1uLL; // Leave
+      a = 1ULL; // Upper
+      a = 1ull; // Lower
+
+    Possible values:
+
+    * ``NLCS_Leave`` (in configuration: ``Leave``)
+      Leave this component of the literal as is.
+
+    * ``NLCS_Upper`` (in configuration: ``Upper``)
+      Format this component with uppercase characters.
+
+    * ``NLCS_Lower`` (in configuration: ``Lower``)
+      Format this component with lowercase characters.
+
+
+
 .. _ObjCBinPackProtocolList:
 
 **ObjCBinPackProtocolList** (``BinPackStyle``) :versionbadge:`clang-format 7` :ref:`¶ <ObjCBinPackProtocolList>`

clang/docs/ReleaseNotes.rst

@@ -468,6 +468,8 @@ AST Matchers
 clang-format
 ------------
 - Add ``SpaceInEmptyBraces`` option and set it to ``Always`` for WebKit style.
+- Add ``NumericLiteralCase`` option for enforcing character case in numeric
+  literals.
 
 libclang
 --------

clang/include/clang/Format/Format.h

@@ -3558,6 +3558,73 @@ struct FormatStyle {
   /// \version 9
   std::vector<std::string> NamespaceMacros;
 
+  /// Control over each component in a numeric literal.
+  enum NumericLiteralComponentStyle : int8_t {
+    /// Leave this component of the literal as is.
+    NLCS_Leave,
+    /// Format this component with uppercase characters.
+    NLCS_Upper,
+    /// Format this component with lowercase characters.
+    NLCS_Lower,
+  };
+
+  /// Separate control for each numeric literal component.
+  ///
+  /// For example, the config below will leave exponent letters alone, reformat
+  /// hexadecimal digits in lowercase, reformat numeric literal prefixes in
+  /// uppercase, and reformat suffixes in lowercase.
+  /// \code
+  ///   NumericLiteralCase:
+  ///     ExponentLetter: Leave
+  ///     HexDigit: Lower
+  ///     Prefix: Upper
+  ///     Suffix: Lower
+  /// \endcode
+  struct NumericLiteralCaseStyle {
+    /// Format floating point exponent separator letter case.
+    /// \code
+    ///   float a = 6.02e23 + 1.0E10; // Leave
+    ///   float a = 6.02E23 + 1.0E10; // Upper
+    ///   float a = 6.02e23 + 1.0e10; // Lower
+    /// \endcode
+    NumericLiteralComponentStyle ExponentLetter;
+    /// Format hexadecimal digit case.
+    /// \code
+    ///   a = 0xaBcDeF; // Leave
+    ///   a = 0xABCDEF; // Upper
+    ///   a = 0xabcdef; // Lower
+    /// \endcode
+    NumericLiteralComponentStyle HexDigit;
+    /// Format integer prefix case.
+    /// \code
+    ///    a = 0XF0 | 0b1; // Leave
+    ///    a = 0XF0 | 0B1; // Upper
+    ///    a = 0xF0 | 0b1; // Lower
+    /// \endcode
+    NumericLiteralComponentStyle Prefix;
+    /// Format suffix case. This option excludes case-sensitive reserved
+    /// suffixes, such as ``min`` in C++.
+    /// \code
+    ///   a = 1uLL; // Leave
+    ///   a = 1ULL; // Upper
+    ///   a = 1ull; // Lower
+    /// \endcode
+    NumericLiteralComponentStyle Suffix;
+
+    bool operator==(const NumericLiteralCaseStyle &R) const {
+      return ExponentLetter == R.ExponentLetter && HexDigit == R.HexDigit &&
+             Prefix == R.Prefix && Suffix == R.Suffix;
+    }
+
+    bool operator!=(const NumericLiteralCaseStyle &R) const {
+      return !(*this == R);
+    }
+  };
+
+  /// Capitalization style for numeric literals.
+  /// \version 22
+  NumericLiteralCaseStyle NumericLiteralCase;
+
   /// Controls bin-packing Objective-C protocol conformance list
   /// items into as few lines as possible when they go over ``ColumnLimit``.
   ///
@@ -5469,6 +5536,7 @@ struct FormatStyle {
            MaxEmptyLinesToKeep == R.MaxEmptyLinesToKeep &&
            NamespaceIndentation == R.NamespaceIndentation &&
            NamespaceMacros == R.NamespaceMacros &&
+           NumericLiteralCase == R.NumericLiteralCase &&
            ObjCBinPackProtocolList == R.ObjCBinPackProtocolList &&
            ObjCBlockIndentWidth == R.ObjCBlockIndentWidth &&
            ObjCBreakBeforeNestedBlockParam ==

clang/lib/Format/CMakeLists.txt

@@ -13,6 +13,7 @@ add_clang_library(clangFormat
   MacroExpander.cpp
   MatchFilePath.cpp
   NamespaceEndCommentsFixer.cpp
+  NumericLiteralCaseFixer.cpp
   NumericLiteralInfo.cpp
   ObjCPropertyAttributeOrderFixer.cpp
   QualifierAlignmentFixer.cpp

clang/lib/Format/Format.cpp

@@ -16,6 +16,7 @@
 #include "DefinitionBlockSeparator.h"
 #include "IntegerLiteralSeparatorFixer.h"
 #include "NamespaceEndCommentsFixer.h"
+#include "NumericLiteralCaseFixer.h"
 #include "ObjCPropertyAttributeOrderFixer.h"
 #include "QualifierAlignmentFixer.h"
 #include "SortJavaScriptImports.h"
@@ -472,6 +473,25 @@ struct ScalarEnumerationTraits<FormatStyle::NamespaceIndentationKind> {
   }
 };
 
+template <>
+struct ScalarEnumerationTraits<FormatStyle::NumericLiteralComponentStyle> {
+  static void enumeration(IO &IO,
+                          FormatStyle::NumericLiteralComponentStyle &Value) {
+    IO.enumCase(Value, "Leave", FormatStyle::NLCS_Leave);
+    IO.enumCase(Value, "Upper", FormatStyle::NLCS_Upper);
+    IO.enumCase(Value, "Lower", FormatStyle::NLCS_Lower);
+  }
+};
+
+template <> struct MappingTraits<FormatStyle::NumericLiteralCaseStyle> {
+  static void mapping(IO &IO, FormatStyle::NumericLiteralCaseStyle &Value) {
+    IO.mapOptional("ExponentLetter", Value.ExponentLetter);
+    IO.mapOptional("HexDigit", Value.HexDigit);
+    IO.mapOptional("Prefix", Value.Prefix);
+    IO.mapOptional("Suffix", Value.Suffix);
+  }
+};
+
 template <> struct ScalarEnumerationTraits<FormatStyle::OperandAlignmentStyle> {
   static void enumeration(IO &IO, FormatStyle::OperandAlignmentStyle &Value) {
     IO.enumCase(Value, "DontAlign", FormatStyle::OAS_DontAlign);
@@ -1121,6 +1141,7 @@ template <> struct MappingTraits<FormatStyle> {
     IO.mapOptional("MaxEmptyLinesToKeep", Style.MaxEmptyLinesToKeep);
     IO.mapOptional("NamespaceIndentation", Style.NamespaceIndentation);
     IO.mapOptional("NamespaceMacros", Style.NamespaceMacros);
+    IO.mapOptional("NumericLiteralCase", Style.NumericLiteralCase);
     IO.mapOptional("ObjCBinPackProtocolList", Style.ObjCBinPackProtocolList);
     IO.mapOptional("ObjCBlockIndentWidth", Style.ObjCBlockIndentWidth);
     IO.mapOptional("ObjCBreakBeforeNestedBlockParam",
@@ -1653,6 +1674,10 @@ FormatStyle getLLVMStyle(FormatStyle::LanguageKind Language) {
   LLVMStyle.LineEnding = FormatStyle::LE_DeriveLF;
   LLVMStyle.MaxEmptyLinesToKeep = 1;
   LLVMStyle.NamespaceIndentation = FormatStyle::NI_None;
+  LLVMStyle.NumericLiteralCase = {/*ExponentLetter=*/FormatStyle::NLCS_Leave,
+                                  /*HexDigit=*/FormatStyle::NLCS_Leave,
+                                  /*Prefix=*/FormatStyle::NLCS_Leave,
+                                  /*Suffix=*/FormatStyle::NLCS_Leave};
   LLVMStyle.ObjCBinPackProtocolList = FormatStyle::BPS_Auto;
   LLVMStyle.ObjCBlockIndentWidth = 2;
   LLVMStyle.ObjCBreakBeforeNestedBlockParam = true;
@@ -3890,6 +3915,10 @@ reformat(const FormatStyle &Style, StringRef Code,
     return IntegerLiteralSeparatorFixer().process(Env, Expanded);
   });
 
+  Passes.emplace_back([&](const Environment &Env) {
+    return NumericLiteralCaseFixer().process(Env, Expanded);
+  });
+
   if (Style.isCpp()) {
     if (Style.QualifierAlignment != FormatStyle::QAS_Leave)
       addQualifierAlignmentFixerPasses(Expanded, Passes);