find_package(): Refactor CMAKE_[SYSTEM_]IGNORE_PATH

In the old implementation, CMAKE_[SYSTEM_]IGNORE_PATH was handled
in cmFindCommon. Move it into cmFindPackageCommand.

Source/cmFindBase.cxx

@@ -168,7 +168,7 @@ bool cmFindBase::ParseArguments(std::vector<std::string> const& argsIn)
   }
   this->ExpandPaths();
 
-  this->ComputeFinalPaths();
+  this->ComputeFinalPaths(IgnorePaths::Yes);
 
   return true;
 }

Source/cmFindCommon.cxx

@@ -283,14 +283,15 @@ void cmFindCommon::RerootPaths(std::vector<std::string>& paths)
 
 void cmFindCommon::GetIgnoredPaths(std::vector<std::string>& ignore)
 {
-  // null-terminated list of paths.
-  static const char* paths[] = { "CMAKE_SYSTEM_IGNORE_PATH",
-                                 "CMAKE_IGNORE_PATH", nullptr };
+  static constexpr const char* paths[] = {
+    "CMAKE_SYSTEM_IGNORE_PATH",
+    "CMAKE_IGNORE_PATH",
+  };
 
   // Construct the list of path roots with no trailing slashes.
-  for (const char** pathName = paths; *pathName; ++pathName) {
+  for (const char* pathName : paths) {
     // Get the list of paths to ignore from the variable.
-    this->Makefile->GetDefExpandList(*pathName, ignore);
+    this->Makefile->GetDefExpandList(pathName, ignore);
   }
 
   for (std::string& i : ignore) {
@@ -365,11 +366,13 @@ static void AddTrailingSlash(std::string& s)
     s += '/';
   }
 }
-void cmFindCommon::ComputeFinalPaths()
+void cmFindCommon::ComputeFinalPaths(IgnorePaths ignorePaths)
 {
   // Filter out ignored paths from the prefix list
   std::set<std::string> ignored;
-  this->GetIgnoredPaths(ignored);
+  if (ignorePaths == IgnorePaths::Yes) {
+    this->GetIgnoredPaths(ignored);
+  }
 
   // Combine the separate path types, filtering out ignores
   this->SearchPaths.clear();

Source/cmFindCommon.h

@@ -82,12 +82,17 @@ protected:
   /** Place a set of search paths under the search roots.  */
   void RerootPaths(std::vector<std::string>& paths);
 
-  /** Get ignored paths from CMAKE_[SYSTEM_]IGNORE_path variables.  */
+  /** Get ignored paths from CMAKE_[SYSTEM_]IGNORE_PATH variables.  */
   void GetIgnoredPaths(std::vector<std::string>& ignore);
   void GetIgnoredPaths(std::set<std::string>& ignore);
 
   /** Compute final search path list (reroot + trailing slash).  */
-  void ComputeFinalPaths();
+  enum class IgnorePaths
+  {
+    No,
+    Yes,
+  };
+  void ComputeFinalPaths(IgnorePaths ignorePaths);
 
   /** Compute the current default root path mode.  */
   void SelectDefaultRootPathMode();

Source/cmFindPackageCommand.cxx

@@ -1346,7 +1346,7 @@ void cmFindPackageCommand::ComputePrefixes()
   }
   this->FillPrefixesUserGuess();
 
-  this->ComputeFinalPaths();
+  this->ComputeFinalPaths(IgnorePaths::No);
 }
 
 void cmFindPackageCommand::FillPrefixesPackageRoot()
@@ -2286,6 +2286,15 @@ bool cmFindPackageCommand::SearchPrefix(std::string const& prefix_in)
     return false;
   }
 
+  // Skip this if it's in ignored paths.
+  std::string prefixWithoutSlash = prefix_in;
+  if (prefixWithoutSlash != "/" && prefixWithoutSlash.back() == '/') {
+    prefixWithoutSlash.erase(prefixWithoutSlash.length() - 1);
+  }
+  if (this->IgnoredPaths.count(prefixWithoutSlash)) {
+    return false;
+  }
+
   //  PREFIX/ (useful on windows or in build trees)
   if (this->SearchDirectory(prefix_in)) {
     return true;