Autogen: Restore AUTOUIC lookup paths from 3.8.2

When encountering an `#include "<PATH>ui_<BASE>.h"` statement,
search for `<BASE>.ui` in
 - <SOURCE_DIR>/<BASE>.ui
 - <SOURCE_DIR>/<PATH><BASE>.ui
 - <AUTOUIC_SEARCH_PATH>/<BASE>.ui
 - <AUTOUIC_SEARCH_PATH>/<PATH><BASE>.ui

In CMake 3.8.2 the lookup list was
  - <SOURCE_DIR>/<BASE>.ui

In CMake 3.9.[01] the lookup list was
 - <SOURCE_DIR>/<PATH><BASE.ui>
 - <AUTOUIC_SEARCH_PATH>/<PATH><BASE>.ui

Closes #17168

Source/cmQtAutoGenerators.cxx

@@ -1446,31 +1446,62 @@ bool cmQtAutoGenerators::MocGenerateFile(
 
 bool cmQtAutoGenerators::UicFindIncludedFile(std::string& absFile,
                                              const std::string& sourceFile,
-                                             const std::string& includeString)
+                                             const std::string& searchPath,
+                                             const std::string& searchFile)
 {
   bool success = false;
-  // Search in vicinity of the source
+  std::vector<std::string> testFiles;
+  // Collect search paths list
   {
-    std::string testPath = SubDirPrefix(sourceFile);
-    testPath += includeString;
-    if (cmsys::SystemTools::FileExists(testPath.c_str())) {
-      absFile = cmsys::SystemTools::GetRealPath(testPath);
+    const std::string searchFileFull = searchPath + searchFile;
+    // Vicinity of the source
+    {
+      const std::string sourcePath = SubDirPrefix(sourceFile);
+      testFiles.push_back(sourcePath + searchFile);
+      if (!searchPath.empty()) {
+        testFiles.push_back(sourcePath + searchFileFull);
+      }
+    }
+    // AUTOUIC search paths
+    if (!this->UicSearchPaths.empty()) {
+      for (std::vector<std::string>::const_iterator iit =
+             this->UicSearchPaths.begin();
+           iit != this->UicSearchPaths.end(); ++iit) {
+        testFiles.push_back(*iit + "/" + searchFile);
+      }
+      if (!searchPath.empty()) {
+        for (std::vector<std::string>::const_iterator iit =
+               this->UicSearchPaths.begin();
+             iit != this->UicSearchPaths.end(); ++iit) {
+          testFiles.push_back(*iit + "/" + searchFileFull);
+        }
+      }
+    }
+  }
+
+  // Search for the .ui file!
+  for (std::vector<std::string>::const_iterator iit = testFiles.begin();
+       iit != testFiles.end(); ++iit) {
+    const std::string& testFile = *iit;
+    if (cmsys::SystemTools::FileExists(testFile.c_str())) {
+      absFile = cmsys::SystemTools::GetRealPath(testFile);
       success = true;
+      break;
     }
   }
-  // Search in include directories
+
+  // Log error
   if (!success) {
-    for (std::vector<std::string>::const_iterator iit =
-           this->UicSearchPaths.begin();
-         iit != this->UicSearchPaths.end(); ++iit) {
-      const std::string fullPath = ((*iit) + '/' + includeString);
-      if (cmsys::SystemTools::FileExists(fullPath.c_str())) {
-        absFile = cmsys::SystemTools::GetRealPath(fullPath);
-        success = true;
-        break;
-      }
+    std::ostringstream ost;
+    ost << "AutoUic: Error: " << Quoted(sourceFile) << "\n";
+    ost << "Could not find " << Quoted(searchFile) << " in\n";
+    for (std::vector<std::string>::const_iterator iit = testFiles.begin();
+         iit != testFiles.end(); ++iit) {
+      ost << "  " << Quoted(*iit) << "\n";
     }
+    this->LogError(ost.str());
   }
+
   return success;
 }
 
@@ -1500,16 +1531,14 @@ bool cmQtAutoGenerators::UicGenerateAll(
         const std::string uiBasePath = SubDirPrefix(*uit);
         const std::string uiBaseName =
           cmsys::SystemTools::GetFilenameWithoutLastExtension(*uit).substr(3);
-        const std::string searchFileName = uiBasePath + uiBaseName + ".ui";
+        const std::string uiFileName = uiBaseName + ".ui";
         std::string uiInputFile;
-        if (UicFindIncludedFile(uiInputFile, source, searchFileName)) {
+        if (UicFindIncludedFile(uiInputFile, source, uiBasePath, uiFileName)) {
           std::string uiOutputFile = uiBasePath + "ui_" + uiBaseName + ".h";
           cmSystemTools::ReplaceString(uiOutputFile, "..", "__");
           uiGenMap[uiInputFile] = uiOutputFile;
           testMap[uiInputFile] = uiOutputFile;
         } else {
-          this->LogError("AutoUic: Error: " + Quoted(sit->first) +
-                         "\nCould not find " + Quoted(searchFileName));
           return false;
         }
       }

Source/cmQtAutoGenerators.h

@@ -112,7 +112,8 @@ private:
 
   // -- Uic file generation
   bool UicFindIncludedFile(std::string& absFile, const std::string& sourceFile,
-                           const std::string& includeString);
+                           const std::string& searchPath,
+                           const std::string& searchFile);
   bool UicGenerateAll(
     const std::map<std::string, std::vector<std::string> >& includedUis);
   bool UicGenerateFile(const std::string& realName,