From 75b6191dffe3043d99eed1a60ce0c612125ff39c Mon Sep 17 00:00:00 2001
From: Victor Romero <viromer@microsoft.com>
Date: Wed, 27 Oct 2021 10:36:59 -0700
Subject: [PATCH] [vcpkg_download_distfile] Check SHA512 for already downloaded
 files (#20988)

* [vcpkg_download_distfile] Check SHA512 for already downloaded files

* [vcpkg_download_distfile] Respect SKIP_SHA512 to enable --head
---
 scripts/cmake/vcpkg_download_distfile.cmake | 39 +++++++++++++++------
 1 file changed, 28 insertions(+), 11 deletions(-)

diff --git a/scripts/cmake/vcpkg_download_distfile.cmake b/scripts/cmake/vcpkg_download_distfile.cmake
index 8bbe9e3b574..08a039c0518 100644
--- a/scripts/cmake/vcpkg_download_distfile.cmake
+++ b/scripts/cmake/vcpkg_download_distfile.cmake
@@ -58,7 +58,7 @@ The helper [`vcpkg_from_github`](vcpkg_from_github.md) should be used for downlo
 * [freetype](https://github.com/Microsoft/vcpkg/blob/master/ports/freetype/portfile.cmake)
 #]===]
 
-function(z_vcpkg_download_distfile_test_hash path kind error_advice sha512 skip_sha512)
+function(z_vcpkg_download_distfile_test_hash file_path kind error_advice sha512 skip_sha512)
     if(_VCPKG_INTERNAL_NO_HASH_CHECK)
         # When using the internal hash skip, do not output an explicit message.
         return()
@@ -68,14 +68,14 @@ function(z_vcpkg_download_distfile_test_hash path kind error_advice sha512 skip_
         return()
     endif()
 
-    file(SHA512 "${path}" file_hash)
+    file(SHA512 "${file_path}" file_hash)
     if(NOT "${file_hash}" STREQUAL "${sha512}")
         message(FATAL_ERROR
             "\nFile does not have expected hash:\n"
             "        File path: [ ${file_path} ]\n"
             "    Expected hash: [ ${sha512} ]\n"
             "      Actual hash: [ ${file_hash} ]\n"
-            "${CUSTOM_ERROR_ADVICE}\n")
+            "${error_advice}\n")
     endif()
 endfunction()
 
@@ -204,21 +204,38 @@ If you do not know the SHA512, add it as 'SHA512 0' and re-run this command.")
     file(REMOVE_RECURSE "${DOWNLOADS}/temp")
     file(MAKE_DIRECTORY "${DOWNLOADS}/temp")
 
+    # check if file with same name already exists in downloads
+    if(EXISTS "${downloaded_file_path}")
+        set(advice_message "The cached file SHA512 doesn't match. The file may have been corrupted.")
+        if(_VCPKG_NO_DOWNLOADS)
+            string(APPEND advice_message " Downloads are disabled please provide a valid file at path ${downloaded_file_path} and retry.")
+        else()
+            string(APPEND advice_message " To re-download this file please delete cached file at path ${downloaded_file_path} and retry.")
+        endif()
+
+        z_vcpkg_download_distfile_test_hash(
+            "${downloaded_file_path}"
+            "cached file"
+            "${advice_message}"
+            "${arg_SHA512}"
+            "${arg_SKIP_SHA512}"
+        )
+
+        if(NOT vcpkg_download_distfile_QUIET)
+            message(STATUS "Using cached ${arg_FILENAME}.")
+        endif()
+        
+        # Suppress the "Downloading ${arg_URLS} -> ${arg_FILENAME}..." message
+        set(vcpkg_download_distfile_QUIET TRUE)
+    endif()
+
     # vcpkg_download_distfile_ALWAYS_REDOWNLOAD only triggers when NOT _VCPKG_NO_DOWNLOADS
     # this could be de-morgan'd out but it's more clear this way
     if(_VCPKG_NO_DOWNLOADS)
         if(NOT EXISTS "${downloaded_file_path}")
             message(FATAL_ERROR "Downloads are disabled, but '${downloaded_file_path}' does not exist.")
         endif()
-        if(NOT arg_QUIET)
-            message(STATUS "Using ${downloaded_file_path}")
-        endif()
 
-        z_vcpkg_download_distfile_test_hash(
-            "${downloaded_file_path}"
-            "cached file"
-            "Please delete the file and retry if this file should be downloaded again."
-        )
         set("${out_var}" "${downloaded_file_path}" PARENT_SCOPE)
         return()
     endif()