feat: print suggested Bazel flags based on package language standard …

…settings (#644)

- Include the `cLanguageStandard` and `cxxLanguageStandard` settings in
the Swift dependency index JSON.
- Print suggested Bazel flags based upon the language standard settings.

Related to #510.

examples/firebase_example/.bazelrc

@@ -7,11 +7,14 @@ import %workspace%/../../ci.bazelrc
 # Try to import a local.rc file; typically, written by CI
 try-import %workspace%/../../local.bazelrc
 
-# Per https://github.com/firebase/firebase-ios-sdk/blob/master/Package.swift#L1322-L1323
 # NOTE: Puposefully not specifying --copt='-std=c99' as it is applied to 
 # objc_library targets that contain Objective-C++ files. Tried using 
 # --per_file_copt to exclude .mm files, but did not have success.
 # https://stackoverflow.com/questions/40260242/how-to-set-c-standard-version-when-build-with-bazel/43388168#43388168
+#
+# # Required by firebase-ios-sdk, googleappmeasurement, googledatatransport, googleutilities
+# build --copt='-std=c99'
+# Required by firebase-ios-sdk, googleappmeasurement, googledatatransport, googleutilities, leveldb
 build --cxxopt='-std=gnu++14'
 
 # Firebase SPM support requires `-ObjC` linker option.

examples/firebase_example/swift_deps_index.json

@@ -1554,7 +1554,9 @@
         "commit": "837d4af6ead57cec1fc38007892500d3139c7556",
         "remote": "https://github.com/firebase/firebase-ios-sdk",
         "version": "10.16.0"
-      }
+      },
+      "cLanguageStandard": "c99",
+      "cxxLanguageStandard": "gnu++14"
     },
     {
       "name": "swiftpkg_googleappmeasurement",
@@ -1563,7 +1565,9 @@
         "commit": "56f681586ff006a7982b53dc94082eea31971acf",
         "remote": "https://github.com/google/GoogleAppMeasurement.git",
         "version": "10.16.0"
-      }
+      },
+      "cLanguageStandard": "c99",
+      "cxxLanguageStandard": "gnu++14"
     },
     {
       "name": "swiftpkg_googledatatransport",
@@ -1572,7 +1576,9 @@
         "commit": "5056b15c5acbb90cd214fe4d6138bdf5a740e5a8",
         "remote": "https://github.com/google/GoogleDataTransport.git",
         "version": "9.2.0"
-      }
+      },
+      "cLanguageStandard": "c99",
+      "cxxLanguageStandard": "gnu++14"
     },
     {
       "name": "swiftpkg_googleutilities",
@@ -1581,7 +1587,9 @@
         "commit": "0543562f85620b5b7c510c6bcbef75b562a5127b",
         "remote": "https://github.com/google/GoogleUtilities.git",
         "version": "7.11.0"
-      }
+      },
+      "cLanguageStandard": "c99",
+      "cxxLanguageStandard": "gnu++14"
     },
     {
       "name": "swiftpkg_grpc_binary",
@@ -1617,7 +1625,8 @@
         "commit": "0706abcc6b0bd9cedfbb015ba840e4a780b5159b",
         "remote": "https://github.com/firebase/leveldb.git",
         "version": "1.22.2"
-      }
+      },
+      "cxxLanguageStandard": "gnu++14"
     },
     {
       "name": "swiftpkg_nanopb",

examples/soto_example/.bazelrc

@@ -10,4 +10,5 @@ try-import %workspace%/../../local.bazelrc
 # The CNIOBoringSSL uses C++14 features like 'enable_if_t' macro support.
 # For more details on how to enable this in Bazel: 
 # https://stackoverflow.com/questions/40260242/how-to-set-c-standard-version-when-build-with-bazel/43388168#43388168
+# Required by swift-nio-ssl
 build --cxxopt='-std=c++14'

examples/soto_example/swift_deps_index.json

@@ -7228,7 +7228,8 @@
         "commit": "4fb7ead803e38949eb1d6fabb849206a72c580f3",
         "remote": "https://github.com/apple/swift-nio-ssl.git",
         "version": "2.23.0"
-      }
+      },
+      "cxxLanguageStandard": "c++14"
     },
     {
       "name": "swiftpkg_swift_nio_transport_services",

examples/vapor_example/.bazelrc

@@ -10,5 +10,8 @@ try-import %workspace%/../../local.bazelrc
 # The CNIOBoringSSL uses C++14 features like 'enable_if_t' macro support.
 # For more details on how to enable this in Bazel: 
 # https://stackoverflow.com/questions/40260242/how-to-set-c-standard-version-when-build-with-bazel/43388168#43388168
+#
+# # Required by swift-crypto
+# build --cxxopt='-std=c++11'
+# Required by swift-nio-ssl
 build --cxxopt='-std=c++14'
-

examples/vapor_example/swift/deps_index.json

@@ -1432,7 +1432,8 @@
         "commit": "75ec60b8b4cc0f085c3ac414f3dca5625fa3588e",
         "remote": "https://github.com/apple/swift-crypto.git",
         "version": "2.2.4"
-      }
+      },
+      "cxxLanguageStandard": "c++11"
     },
     {
       "name": "swiftpkg_swift_log",
@@ -1486,7 +1487,8 @@
         "commit": "320bd978cceb8e88c125dcbb774943a92f6286e9",
         "remote": "https://github.com/apple/swift-nio-ssl.git",
         "version": "2.25.0"
-      }
+      },
+      "cxxLanguageStandard": "c++14"
     },
     {
       "name": "swiftpkg_swift_nio_transport_services",

examples/xcmetrics_example/.bazelrc

@@ -10,5 +10,8 @@ try-import %workspace%/../../local.bazelrc
 # The CNIOBoringSSL uses C++14 features like 'enable_if_t' macro support.
 # For more details on how to enable this in Bazel: 
 # https://stackoverflow.com/questions/40260242/how-to-set-c-standard-version-when-build-with-bazel/43388168#43388168
+#
+# # Required by jwt-kit, swift-crypto
+# build --cxxopt='-std=c++11'
+# Required by swift-nio-ssl
 build --cxxopt='-std=c++14'
-

examples/xcmetrics_example/swift_deps_index.json

@@ -7024,7 +7024,8 @@
         "commit": "dcd78f07e092ac9138327e2bfbb0687a55a80850",
         "remote": "https://github.com/vapor/jwt-kit.git",
         "version": "4.8.0"
-      }
+      },
+      "cxxLanguageStandard": "c++11"
     },
     {
       "name": "swiftpkg_mobius.swift",
@@ -7231,7 +7232,8 @@
         "commit": "75ec60b8b4cc0f085c3ac414f3dca5625fa3588e",
         "remote": "https://github.com/apple/swift-crypto.git",
         "version": "2.2.4"
-      }
+      },
+      "cxxLanguageStandard": "c++11"
     },
     {
       "name": "swiftpkg_swift_log",
@@ -7285,7 +7287,8 @@
         "commit": "4fb7ead803e38949eb1d6fabb849206a72c580f3",
         "remote": "https://github.com/apple/swift-nio-ssl.git",
         "version": "2.23.0"
-      }
+      },
+      "cxxLanguageStandard": "c++14"
     },
     {
       "name": "swiftpkg_swift_nio_transport_services",

gazelle/internal/spdump/manifest.go

@@ -20,9 +20,11 @@ func NewManifestFromJSON(bytes []byte) (*Manifest, error) {
 
 // A Manifest represents a Swift manifest as serialized by `swift package dump-package`.
 type Manifest struct {
-	Name         string
-	Dependencies []Dependency
-	Platforms    []Platform
-	Products     []Product
-	Targets      Targets
+	Name                string
+	Dependencies        []Dependency
+	Platforms           []Platform
+	Products            []Product
+	Targets             Targets
+	CLanguageStandard   string `json:"cLanguageStandard"`
+	CxxLanguageStandard string `json:"cxxLanguageStandard"`
 }

gazelle/internal/spdump/manifest_test.go

@@ -21,7 +21,7 @@ func TestNewManifestFromJSON(t *testing.T) {
 					},
 					Requirement: &spdump.DependencyRequirement{
 						Ranges: []*spdump.VersionRange{
-							&spdump.VersionRange{LowerBound: "1.2.0", UpperBound: "2.0.0"},
+							{LowerBound: "1.2.0", UpperBound: "2.0.0"},
 						},
 					},
 				},
@@ -68,6 +68,8 @@ func TestNewManifestFromJSON(t *testing.T) {
 				Settings: []spdump.TargetSetting{},
 			},
 		},
+		CLanguageStandard:   "c99",
+		CxxLanguageStandard: "gnu++14",
 	}
 	manifest, err := spdump.NewManifestFromJSON([]byte(swiftPackageJSONStr))
 	assert.NoError(t, err)
@@ -76,8 +78,8 @@ func TestNewManifestFromJSON(t *testing.T) {
 
 const swiftPackageJSONStr = `
 {
-  "cLanguageStandard" : null,
-  "cxxLanguageStandard" : null,
+  "cLanguageStandard" : "c99",
+  "cxxLanguageStandard" : "gnu++14",
   "dependencies" : [
     {
       "sourceControl" : [

gazelle/internal/swift/dependency_index.go

@@ -142,6 +142,10 @@ func (di *DependencyIndex) DirectDepPackages() []*Package {
 	return results
 }
 
+func (di *DependencyIndex) Packages() []*Package {
+	return di.packageIndex.Packages()
+}
+
 // Resolve
 
 type ModuleResolutionResult struct {

gazelle/internal/swift/package.go

@@ -8,10 +8,12 @@ import (
 )
 
 type Package struct {
-	Name     string         `json:"name"`
-	Identity string         `json:"identity"`
-	Local    *LocalPackage  `json:"local,omitempty"`
-	Remote   *RemotePackage `json:"remote,omitempty"`
+	Name                string         `json:"name"`
+	Identity            string         `json:"identity"`
+	Local               *LocalPackage  `json:"local,omitempty"`
+	Remote              *RemotePackage `json:"remote,omitempty"`
+	CLanguageStandard   string         `json:"cLanguageStandard,omitempty"`
+	CxxLanguageStandard string         `json:"cxxLanguageStandard,omitempty"`
 }
 
 type LocalPackage struct {
@@ -33,7 +35,18 @@ func NewPackageFromBazelRepo(
 	patch *Patch,
 ) (*Package, error) {
 	var err error
-	p := Package{Name: bzlRepo.Name, Identity: bzlRepo.Identity}
+	cLangStd := ""
+	cxxLangStd := ""
+	if bzlRepo.PkgInfo != nil {
+		cLangStd = bzlRepo.PkgInfo.CLanguageStandard
+		cxxLangStd = bzlRepo.PkgInfo.CxxLanguageStandard
+	}
+	p := Package{
+		Name:                bzlRepo.Name,
+		Identity:            bzlRepo.Identity,
+		CLanguageStandard:   cLangStd,
+		CxxLanguageStandard: cxxLangStd,
+	}
 	if bzlRepo.Pin != nil {
 		p.Remote, err = remotePackageFromPin(bzlRepo.Name, bzlRepo.Pin)
 		if err != nil {

gazelle/internal/swiftpkg/package_info.go

@@ -12,14 +12,16 @@ import (
 
 // A PackageInfo encapsulates all of the information about a Swift package.
 type PackageInfo struct {
-	Name         string
-	DisplayName  string
-	Path         string
-	ToolsVersion string
-	Targets      Targets
-	Platforms    []*Platform
-	Products     []*Product
-	Dependencies Dependencies
+	Name                string
+	DisplayName         string
+	Path                string
+	ToolsVersion        string
+	Targets             Targets
+	Platforms           []*Platform
+	Products            []*Product
+	Dependencies        Dependencies
+	CLanguageStandard   string
+	CxxLanguageStandard string
 }
 
 // NewPackageInfo returns the Swift package information from a Swift package on disk.
@@ -90,14 +92,16 @@ func NewPackageInfo(sw swiftbin.Executor, dir string) (*PackageInfo, error) {
 	}
 
 	return &PackageInfo{
-		Name:         descManifest.Name,
-		DisplayName:  descManifest.ManifestDisplayName,
-		Path:         descManifest.Path,
-		ToolsVersion: descManifest.ToolsVersion,
-		Targets:      targets,
-		Platforms:    platforms,
-		Products:     products,
-		Dependencies: deps,
+		Name:                descManifest.Name,
+		DisplayName:         descManifest.ManifestDisplayName,
+		Path:                descManifest.Path,
+		ToolsVersion:        descManifest.ToolsVersion,
+		Targets:             targets,
+		Platforms:           platforms,
+		Products:            products,
+		Dependencies:        deps,
+		CLanguageStandard:   dumpManifest.CLanguageStandard,
+		CxxLanguageStandard: dumpManifest.CxxLanguageStandard,
 	}, nil
 }
 

gazelle/update_repos.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"github.com/bazelbuild/bazel-gazelle/language"
 	"github.com/bazelbuild/bazel-gazelle/rule"
@@ -143,6 +144,9 @@ func importReposFromPackageManifest(args language.ImportReposArgs) language.Impo
 		di.AddPackage(pkg)
 	}
 
+	// Print information about language standards
+	printLanguageStandardInfo(di.Packages())
+
 	// Output a use_repo names for bzlmod.
 	if err := writeBzlmodUseRepoNames(di, sc); err != nil {
 		result.Error = err
@@ -225,6 +229,48 @@ func readResolvedPkgPins(resolvedPkgPath string) (map[string]*spreso.Pin, error)
 	return pinsByIdentity, nil
 }
 
+func printLanguageStandardInfo(pkgs []*swift.Package) {
+	cLangStds := make(map[string][]string)
+	cxxLangStds := make(map[string][]string)
+	for _, pkg := range pkgs {
+		if pkg.CLanguageStandard != "" {
+			idents := cLangStds[pkg.CLanguageStandard]
+			idents = append(idents, pkg.Identity)
+			cLangStds[pkg.CLanguageStandard] = idents
+		}
+		if pkg.CxxLanguageStandard != "" {
+			idents := cxxLangStds[pkg.CxxLanguageStandard]
+			idents = append(idents, pkg.Identity)
+			cxxLangStds[pkg.CxxLanguageStandard] = idents
+		}
+	}
+	var outputLines []string
+	if len(cLangStds) > 0 {
+		for std, idents := range cLangStds {
+			outputLines = append(outputLines,
+				fmt.Sprintf("# Required by %s", strings.Join(idents, ", ")),
+				fmt.Sprintf("build --copt='-std=%s'", std),
+			)
+		}
+	}
+	if len(cxxLangStds) > 0 {
+		for std, idents := range cxxLangStds {
+			outputLines = append(outputLines,
+				fmt.Sprintf("# Required by %s", strings.Join(idents, ", ")),
+				fmt.Sprintf("build --cxxopt='-std=%s'", std),
+			)
+		}
+	}
+
+	if len(outputLines) > 0 {
+		preamble := `One or more of your Swift packages has defined language standard requirements.
+Consider adding the following to your .bazelrc file:
+
+`
+		fmt.Println(preamble + strings.Join(outputLines, "\n"))
+	}
+}
+
 func writeBzlmodUseRepoNames(di *swift.DependencyIndex, sc *swiftcfg.SwiftConfig) error {
 	if !sc.UpdateBzlmodUseRepoNames {
 		return nil