find_package: Use <PACKAGENAME>_ROOT variables as search prefixes

Extend commit eb35d8884b (find_package: Use PackageName_ROOT variables
as search prefixes, 2018-03-15, v3.12.0-rc1~349^2) to also check
upper-case `<PACKAGENAME>_ROOT` variables.  Add policy `CMP0144` to
enable the behavior in a compatible way.

Fixes: #24403

4 files changed, 71 insertions, 1 deletions

diff --git a/Source/cmFindPackageCommand.cxx b/Source/cmFindPackageCommand.cxx
index dd00419..5f1a2c5 100644
--- a/Source/cmFindPackageCommand.cxx
+++ b/Source/cmFindPackageCommand.cxx
@@ -1841,13 +1841,56 @@ void cmFindPackageCommand::PushFindPackageRootPathStack()
     } break;
   }
 
+  // Add root paths from <PACKAGENAME>_ROOT CMake and environment variables,
+  // if they are different than <PackageName>_ROOT, and subject to CMP0144.
+  std::string const rootVAR = cmSystemTools::UpperCase(rootVar);
+  cmValue rootDEF;
+  cm::optional<std::string> rootENV;
+  if (rootVAR != rootVar) {
+    rootDEF = this->Makefile->GetDefinition(rootVAR);
+    if (rootDEF && (rootDEF.IsEmpty() || rootDEF == rootDef)) {
+      rootDEF = nullptr;
+    }
+    rootENV = cmSystemTools::GetEnvVar(rootVAR);
+    if (rootENV && (rootENV->empty() || rootENV == rootEnv)) {
+      rootENV = cm::nullopt;
+    }
+  }
+
+  switch (this->Makefile->GetPolicyStatus(cmPolicies::CMP0144)) {
+    case cmPolicies::WARN:
+      this->Makefile->MaybeWarnCMP0144(rootVAR, rootDEF, rootENV);
+      CM_FALLTHROUGH;
+    case cmPolicies::OLD:
+      // OLD behavior is to ignore the <PACKAGENAME>_ROOT variables.
+      rootDEF = nullptr;
+      rootENV = cm::nullopt;
+      break;
+    case cmPolicies::REQUIRED_IF_USED:
+    case cmPolicies::REQUIRED_ALWAYS:
+      this->Makefile->IssueMessage(
+        MessageType::FATAL_ERROR,
+        cmPolicies::GetRequiredPolicyError(cmPolicies::CMP0144));
+      return;
+    case cmPolicies::NEW: {
+      // NEW behavior is to honor the <PACKAGENAME>_ROOT variables.
+    } break;
+  }
+
   if (rootDef) {
     cmExpandList(*rootDef, rootPaths);
   }
+  if (rootDEF) {
+    cmExpandList(*rootDEF, rootPaths);
+  }
   if (rootEnv) {
     std::vector<std::string> p = cmSystemTools::SplitEnvPath(*rootEnv);
     std::move(p.begin(), p.end(), std::back_inserter(rootPaths));
   }
+  if (rootENV) {
+    std::vector<std::string> p = cmSystemTools::SplitEnvPath(*rootENV);
+    std::move(p.begin(), p.end(), std::back_inserter(rootPaths));
+  }
 }
 
 void cmFindPackageCommand::PopFindPackageRootPathStack()
diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index b640d64..2fc2974 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -228,6 +228,27 @@ void cmMakefile::MaybeWarnCMP0074(std::string const& rootVar, cmValue rootDef,
   }
 }
 
+void cmMakefile::MaybeWarnCMP0144(std::string const& rootVAR, cmValue rootDEF,
+                                  cm::optional<std::string> const& rootENV)
+{
+  // Warn if a <PACKAGENAME>_ROOT variable we may use is set.
+  if ((rootDEF || rootENV) && this->WarnedCMP0144.insert(rootVAR).second) {
+    std::ostringstream w;
+    w << cmPolicies::GetPolicyWarning(cmPolicies::CMP0144) << "\n";
+    if (rootDEF) {
+      w << "CMake variable " << rootVAR << " is set to:\n"
+        << "  " << *rootDEF << "\n";
+    }
+    if (rootENV) {
+      w << "Environment variable " << rootVAR << " is set to:\n"
+        << "  " << *rootENV << "\n";
+    }
+    w << "For compatibility, find_package is ignoring the variable, but "
+         "code in a .cmake module might still use it.";
+    this->IssueMessage(MessageType::AUTHOR_WARNING, w.str());
+  }
+}
+
 cmBTStringRange cmMakefile::GetIncludeDirectoriesEntries() const
 {
   return this->StateSnapshot.GetDirectory().GetIncludeDirectoriesEntries();
diff --git a/Source/cmMakefile.h b/Source/cmMakefile.h
index 247d4dd..3cf6e61 100644
--- a/Source/cmMakefile.h
+++ b/Source/cmMakefile.h
@@ -1013,6 +1013,8 @@ public:
 
   void MaybeWarnCMP0074(std::string const& rootVar, cmValue rootDef,
                         cm::optional<std::string> const& rootEnv);
+  void MaybeWarnCMP0144(std::string const& rootVAR, cmValue rootDEF,
+                        cm::optional<std::string> const& rootENV);
   void MaybeWarnUninitialized(std::string const& variable,
                               const char* sourceFilename) const;
   bool IsProjectFile(const char* filename) const;
@@ -1190,6 +1192,7 @@ private:
   bool CheckSystemVars;
   bool CheckCMP0000;
   std::set<std::string> WarnedCMP0074;
+  std::set<std::string> WarnedCMP0144;
   bool IsSourceFileTryCompile;
   mutable bool SuppressSideEffects;
   ImportedTargetScope CurrentImportedTargetScope = ImportedTargetScope::Local;
diff --git a/Source/cmPolicies.h b/Source/cmPolicies.h
index 568eca3..1eca586 100644
--- a/Source/cmPolicies.h
+++ b/Source/cmPolicies.h
@@ -434,7 +434,10 @@ class cmMakefile;
          3, 25, 0, cmPolicies::WARN)                                          \
   SELECT(POLICY, CMP0143,                                                     \
          "Global property USE_FOLDERS treated as ON by default", 3, 26, 0,    \
-         cmPolicies::WARN)
+         cmPolicies::WARN)                                                    \
+  SELECT(POLICY, CMP0144,                                                     \
+         "find_package uses upper-case <PACKAGENAME>_ROOT variables.", 3, 27, \
+         0, cmPolicies::WARN)
 
 #define CM_SELECT_ID(F, A1, A2, A3, A4, A5, A6) F(A1)
 #define CM_FOR_EACH_POLICY_ID(POLICY)                                         \