Add backward compatibility tests for PackConstructorInitializers

[owenpan]

Reworked the logic for handling the backward compatibility.

[MyDeveloperDay]

It seems a little convoluted, but OK

[owenpan]

In D108882#2971192, @MyDeveloperDay wrote:

It seems a little convoluted, but OK

Will add comments to explain the logic.

clang/lib/Format/Format.cpp

IO.mapOptional("EmptyLineAfterAccessModifier",
                    Style.EmptyLineAfterAccessModifier);
     IO.mapOptional("EmptyLineBeforeAccessModifier",
                    Style.EmptyLineBeforeAccessModifier);
     IO.mapOptional("ExperimentalAutoDetectBinPacking",
                    Style.ExperimentalAutoDetectBinPacking);
 
     IO.mapOptional("PackConstructorInitializers",
                    Style.PackConstructorInitializers);
-    // For backward compatibility.
+    // For backward compatibility:
+    // The default value of ConstructorInitializerAllOnOneLineOrOnePerLine was
+    // false unless BasedOnStyle was Google or Chromium whereas that of
+    // AllowAllConstructorInitializersOnNextLine was always true, so the
+    // equivalent default value of PackConstructorInitializers is PCIS_NextLine
+    // for Google/Chromium or PCIS_BinPack otherwise. If the deprecated options
+    // had a non-default value while PackConstructorInitializers has a default
+    // value, set the latter to an equivalent non-default value if needed.
     StringRef BasedOn;
     IO.mapOptional("BasedOnStyle", BasedOn);
     const bool IsGoogleOrChromium = BasedOn.equals_insensitive("google") ||
                                     BasedOn.equals_insensitive("chromium");
     bool OnCurrentLine = IsGoogleOrChromium;
     bool OnNextLine = true;
     IO.mapOptional("ConstructorInitializerAllOnOneLineOrOnePerLine",
                    OnCurrentLine);
     IO.mapOptional("AllowAllConstructorInitializersOnNextLine", OnNextLine);
-    if (IsGoogleOrChromium &&
-        Style.PackConstructorInitializers == FormatStyle::PCIS_NextLine) {
-      if (!OnCurrentLine)
-        Style.PackConstructorInitializers = FormatStyle::PCIS_BinPack;
-      else if (!OnNextLine)
-        Style.PackConstructorInitializers = FormatStyle::PCIS_CurrentLine;
-    } else if (Style.PackConstructorInitializers == FormatStyle::PCIS_BinPack &&
-               OnCurrentLine) {
+    if (!IsGoogleOrChromium) {
+      if (Style.PackConstructorInitializers == FormatStyle::PCIS_BinPack &&
         Style.PackConstructorInitializers = OnNextLine
                                                 ? FormatStyle::PCIS_NextLine
                                                 : FormatStyle::PCIS_CurrentLine;
       }
+    } else if (Style.PackConstructorInitializers ==
+               FormatStyle::PCIS_NextLine) {
+      if (!OnCurrentLine)
+        Style.PackConstructorInitializers = FormatStyle::PCIS_BinPack;
+      else if (!OnNextLine)
+        Style.PackConstructorInitializers = FormatStyle::PCIS_CurrentLine;
+    }
 
     IO.mapOptional("FixNamespaceComments", Style.FixNamespaceComments);
     IO.mapOptional("ForEachMacros", Style.ForEachMacros);
     IO.mapOptional("IfMacros", Style.IfMacros);
 
     IO.mapOptional("IncludeBlocks", Style.IncludeStyle.IncludeBlocks);
     IO.mapOptional("IncludeCategories", Style.IncludeStyle.IncludeCategories);
     IO.mapOptional("IncludeIsMainRegex", Style.IncludeStyle.IncludeIsMainRegex);

clang/unittests/Format/FormatTest.cpp

TEST_F(FormatTest, ParsesConfiguration) {
   CHECK_PARSE("PackConstructorInitializers: Never", PackConstructorInitializers,
               FormatStyle::PCIS_Never);
   CHECK_PARSE("PackConstructorInitializers: BinPack",
               PackConstructorInitializers, FormatStyle::PCIS_BinPack);
   CHECK_PARSE("PackConstructorInitializers: CurrentLine",
               PackConstructorInitializers, FormatStyle::PCIS_CurrentLine);
   CHECK_PARSE("PackConstructorInitializers: NextLine",
               PackConstructorInitializers, FormatStyle::PCIS_NextLine);
+  // For backward compatibility:
+  CHECK_PARSE("BasedOnStyle: Google\n"
+              "ConstructorInitializerAllOnOneLineOrOnePerLine: true\n"
+              "AllowAllConstructorInitializersOnNextLine: false",
+              PackConstructorInitializers, FormatStyle::PCIS_CurrentLine);
+  Style.PackConstructorInitializers = FormatStyle::PCIS_NextLine;
+  CHECK_PARSE("BasedOnStyle: Google\n"
+              "ConstructorInitializerAllOnOneLineOrOnePerLine: false",
+              PackConstructorInitializers, FormatStyle::PCIS_BinPack);
+  CHECK_PARSE("ConstructorInitializerAllOnOneLineOrOnePerLine: true\n"
+              "AllowAllConstructorInitializersOnNextLine: true",
+              PackConstructorInitializers, FormatStyle::PCIS_NextLine);
+  Style.PackConstructorInitializers = FormatStyle::PCIS_BinPack;
+  CHECK_PARSE("ConstructorInitializerAllOnOneLineOrOnePerLine: true\n"
+              "AllowAllConstructorInitializersOnNextLine: false",
+              PackConstructorInitializers, FormatStyle::PCIS_CurrentLine);
 
   Style.EmptyLineBeforeAccessModifier = FormatStyle::ELBAMS_LogicalBlock;
   CHECK_PARSE("EmptyLineBeforeAccessModifier: Never",
               EmptyLineBeforeAccessModifier, FormatStyle::ELBAMS_Never);
   CHECK_PARSE("EmptyLineBeforeAccessModifier: Leave",
               EmptyLineBeforeAccessModifier, FormatStyle::ELBAMS_Leave);
   CHECK_PARSE("EmptyLineBeforeAccessModifier: LogicalBlock",
               EmptyLineBeforeAccessModifier, FormatStyle::ELBAMS_LogicalBlock);