[R-package] Remove paste0 ambiguity for paths (#612)

* Remove paste0 ambiguity for paths

* Fix equal missing typo

* Get rid of all trailing slashes

R-package/src/install.libs.R

@@ -7,7 +7,7 @@ use_mingw <- FALSE
 if (!use_precompile) {
 
   # Check repository content
-  source_dir <- paste0(R_PACKAGE_SOURCE, "/src/")
+  source_dir <- file.path(R_PACKAGE_SOURCE, "src", fsep = "/")
   setwd(source_dir)
   
   if (!file.exists("_IS_FULL_PACKAGE")) {
@@ -29,14 +29,14 @@ if (!use_precompile) {
   }
   
   # Prepare building package
-  build_dir <- paste0(source_dir, "build/")
+  build_dir <- file.path(source_dir, "build", fsep = "/")
   dir.create(build_dir, recursive = TRUE, showWarnings = FALSE)
   setwd(build_dir)
   
   # Prepare installation steps
   cmake_cmd <- "cmake"
   build_cmd <- "make -j"
-  lib_folder <- paste0(R_PACKAGE_SOURCE, "/src/")
+  lib_folder <- file.path(R_PACKAGE_SOURCE, "src", fsep = "/")
   
   # Check if Windows installation (for gcc vs Visual Studio)
   if (WINDOWS) {
@@ -46,7 +46,7 @@ if (!use_precompile) {
     } else {
       cmake_cmd <- paste0(cmake_cmd, " -DCMAKE_GENERATOR_PLATFORM=x64 ")
       build_cmd <- "cmake --build . --target _lightgbm  --config Release"
-      lib_folder <- paste0(R_PACKAGE_SOURCE, "/src/Release/")
+      lib_folder <- file.path(R_PACKAGE_SOURCE, "src/Release", fsep = "/")
     }
   }
   
@@ -57,24 +57,24 @@ if (!use_precompile) {
   # Install
   system(paste0(cmake_cmd, " .."))
   system(build_cmd)
-  src <- paste0(lib_folder, "lib_lightgbm", SHLIB_EXT)
+  src <- file.path(lib_folder, paste0("lib_lightgbm", SHLIB_EXT), fsep = "/")
   
 } else {
 
   # Has precompiled package
-  lib_folder <- paste0(R_PACKAGE_SOURCE, "/../")
-  if (file.exists(paste0(lib_folder, "lib_lightgbm", SHLIB_EXT))) {
-    src <- paste0(lib_folder, "lib_lightgbm", SHLIB_EXT)
-  } else if (file.exists(paste0(lib_folder, "Release/lib_lightgbm", SHLIB_EXT))){
-    src <- paste0(lib_folder, "Release/lib_lightgbm", SHLIB_EXT) 
+  lib_folder <- file.path(R_PACKAGE_SOURCE, "../", fsep = "/")
+  if (file.exists(file.path(lib_folder, paste0("lib_lightgbm", SHLIB_EXT), fsep = "/"))) {
+    src <- file.path(lib_folder, paste0("lib_lightgbm", SHLIB_EXT), fsep = "/")
+  } else if (file.exists(file.path(lib_folder, paste0("Release/lib_lightgbm", SHLIB_EXT), fsep = "/"))) {
+    src <- file.path(lib_folder, paste0("Release/lib_lightgbm", SHLIB_EXT), fsep = "/") 
   } else {
-    src <- paste0(lib_folder, "windows/x64/DLL/lib_lightgbm", SHLIB_EXT) # Expected result: installation will fail if it is not here or any other
+    src <- file.path(lib_folder, paste0("/windows/x64/DLL/lib_lightgbm", SHLIB_EXT), fsep = "/") # Expected result: installation will fail if it is not here or any other
   }
   
 }
 
 # Check installation correctness
-dest <- file.path(R_PACKAGE_DIR, paste0("libs", R_ARCH))
+dest <- file.path(R_PACKAGE_DIR, paste0("libs", R_ARCH), fsep = "/")
 dir.create(dest, recursive = TRUE, showWarnings = FALSE)
 if (file.exists(src)) {
   cat("Found library file: ", src, " to move to ", dest, sep = "")