From 85721c4c56513e255fde7824c5520fde33f61ed3 Mon Sep 17 00:00:00 2001
From: Matthew Woehlke <matthew.woehlke@kitware.com>
Date: Wed, 12 Feb 2025 11:25:24 -0500
Subject: install(PACKAGE_INFO): Export required components

Modify cmExportPackageInfoGenerator to record not just what packages are
required, but what targets (components) are used by those requirements,
and to populate the requirements' component lists accordingly.
---
 Source/cmExportPackageInfoGenerator.cxx            | 34 ++++++++++++++--------
 Source/cmExportPackageInfoGenerator.h              |  2 +-
 .../RunCMake/PackageInfo/Requirements-check.cmake  |  6 ++--
 3 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/Source/cmExportPackageInfoGenerator.cxx b/Source/cmExportPackageInfoGenerator.cxx
index 211347e..8616e10 100644
--- a/Source/cmExportPackageInfoGenerator.cxx
+++ b/Source/cmExportPackageInfoGenerator.cxx
@@ -127,9 +127,22 @@ void cmExportPackageInfoGenerator::GeneratePackageRequires(
 {
   if (!this->Requirements.empty()) {
     Json::Value& requirements = package["requires"];
+
+    // Build description for each requirement.
     for (auto const& requirement : this->Requirements) {
+      auto data = Json::Value{ Json::objectValue };
+
+      // Add required components.
+      if (!requirement.second.empty()) {
+        auto components = Json::Value{ Json::arrayValue };
+        for (std::string const& component : requirement.second) {
+          components.append(component);
+        }
+        data["components"] = components;
+      }
+
       // TODO: version, hint
-      requirements[requirement] = Json::Value{};
+      requirements[requirement.first] = data;
     }
   }
 }
@@ -257,10 +270,10 @@ bool cmExportPackageInfoGenerator::NoteLinkedTarget(
       return false;
     }
 
+    std::string component = linkedName.substr(prefix.length());
+    this->LinkTargets.emplace(linkedName, cmStrCat(pkgName, ':', component));
     // TODO: Record package version, hint.
-    this->Requirements.emplace(pkgName);
-    this->LinkTargets.emplace(
-      linkedName, cmStrCat(pkgName, ':', linkedName.substr(prefix.length())));
+    this->Requirements[pkgName].emplace(std::move(component));
     return true;
   }
 
@@ -278,16 +291,13 @@ bool cmExportPackageInfoGenerator::NoteLinkedTarget(
       return false;
     }
 
-    auto pkgName =
-      cm::string_view{ linkNamespace.data(), linkNamespace.size() - 2 };
-
+    std::string pkgName{ linkNamespace.data(), linkNamespace.size() - 2 };
+    std::string component = linkedTarget->GetExportName();
     if (pkgName == this->GetPackageName()) {
-      this->LinkTargets.emplace(linkedName,
-                                cmStrCat(':', linkedTarget->GetExportName()));
+      this->LinkTargets.emplace(linkedName, cmStrCat(':', component));
     } else {
-      this->Requirements.emplace(pkgName);
-      this->LinkTargets.emplace(
-        linkedName, cmStrCat(pkgName, ':', linkedTarget->GetExportName()));
+      this->LinkTargets.emplace(linkedName, cmStrCat(pkgName, ':', component));
+      this->Requirements[pkgName].emplace(std::move(component));
     }
     return true;
   }
diff --git a/Source/cmExportPackageInfoGenerator.h b/Source/cmExportPackageInfoGenerator.h
index 6fe1e35..5014252 100644
--- a/Source/cmExportPackageInfoGenerator.h
+++ b/Source/cmExportPackageInfoGenerator.h
@@ -110,5 +110,5 @@ private:
   std::vector<std::string> DefaultConfigurations;
 
   std::map<std::string, std::string> LinkTargets;
-  std::set<std::string> Requirements;
+  std::map<std::string, std::set<std::string>> Requirements;
 };
diff --git a/Tests/RunCMake/PackageInfo/Requirements-check.cmake b/Tests/RunCMake/PackageInfo/Requirements-check.cmake
index 59a212f..a082355 100644
--- a/Tests/RunCMake/PackageInfo/Requirements-check.cmake
+++ b/Tests/RunCMake/PackageInfo/Requirements-check.cmake
@@ -8,8 +8,10 @@ expect_value("${content}" "interface" "components" "libb" "type")
 
 file(READ "${out_dir}/bar.cps" content)
 expect_value("${content}" "bar" "name")
-expect_null("${content}" "requires" "foo")
-expect_null("${content}" "requires" "test")
+expect_array("${content}"      1 "requires"  "foo" "components")
+expect_value("${content}" "libb" "requires"  "foo" "components" 0)
+expect_array("${content}"      1 "requires" "test" "components")
+expect_value("${content}" "liba" "requires" "test" "components" 0)
 expect_value("${content}" "interface" "components" "libc" "type")
 expect_value("${content}" "interface" "components" "libd" "type")
 
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