Windows: Adding default --python_path

On Windows, Bazel client will try to find python.exe in $PATH.
If succeed, then we pretend to add a --python_path option in the least
important bazelrc file.

Fixed https://github.com/bazelbuild/bazel/issues/3717

Change-Id: I8d97b0895f024d8d236f3b4b39f91c41d947a5fa
PiperOrigin-RevId: 168659085

4 files changed, 32 insertions, 10 deletions

diff --git a/src/main/cpp/blaze_util_platform.h b/src/main/cpp/blaze_util_platform.h
index a40ce95939..212c1bc0c6 100644
--- a/src/main/cpp/blaze_util_platform.h
+++ b/src/main/cpp/blaze_util_platform.h
@@ -236,6 +236,12 @@ bool UnlimitResources();
 
 void DetectBashOrDie();
 
+// This function has no effect on Unix platforms.
+// On Windows, this function looks into PATH to find python.exe, if python
+// binary is found then add
+// --default_override=0:build=--python_path=<python/path> into options.
+void EnsurePythonPathOption(std::vector<std::string>* options);
+
 }  // namespace blaze
 
 #endif  // BAZEL_SRC_MAIN_CPP_BLAZE_UTIL_PLATFORM_H_
diff --git a/src/main/cpp/blaze_util_posix.cc b/src/main/cpp/blaze_util_posix.cc
index a53b9316d4..5a4d74857f 100644
--- a/src/main/cpp/blaze_util_posix.cc
+++ b/src/main/cpp/blaze_util_posix.cc
@@ -782,4 +782,8 @@ void DetectBashOrDie() {
   // do nothing.
 }
 
+void EnsurePythonPathOption(vector<string>* options) {
+  // do nothing.
+}
+
 }   // namespace blaze.
diff --git a/src/main/cpp/blaze_util_windows.cc b/src/main/cpp/blaze_util_windows.cc
index 7e779bb808..d3be4c566c 100644
--- a/src/main/cpp/blaze_util_windows.cc
+++ b/src/main/cpp/blaze_util_windows.cc
@@ -1307,7 +1307,7 @@ static string GetBashFromGitOnWin() {
   return bash_exe;
 }
 
-static string GetBashFromPath() {
+static string GetBinaryFromPath(const string& binary_name) {
   char found[MAX_PATH];
   string path_list = blaze::GetEnv("PATH");
 
@@ -1324,14 +1324,14 @@ static string GetBashFromPath() {
     if (path.size() > 1 && path[0] == '"' && path[path.size() - 1] == '"') {
       path = path.substr(1, path.size() - 2);
     }
-    if (SearchPathA(path.c_str(),   // _In_opt_  LPCTSTR lpPath,
-                    "bash.exe",     // _In_      LPCTSTR lpFileName,
-                    0,              // LPCTSTR lpExtension,
-                    sizeof(found),  // DWORD   nBufferLength,
-                    found,          // _Out_     LPTSTR  lpBuffer,
-                    0               // _Out_opt_ LPTSTR  *lpFilePart
+    if (SearchPathA(path.c_str(),         // _In_opt_  LPCTSTR lpPath,
+                    binary_name.c_str(),  // _In_      LPCTSTR lpFileName,
+                    0,                    // LPCTSTR lpExtension,
+                    sizeof(found),        // DWORD   nBufferLength,
+                    found,                // _Out_     LPTSTR  lpBuffer,
+                    0                     // _Out_opt_ LPTSTR  *lpFilePart
                     )) {
-      debug_log("bash.exe found on PATH: %s", found);
+      debug_log("%s found on PATH: %s", binary_name.c_str(), found);
       return string(found);
     }
     if (end == string::npos) {
@@ -1340,7 +1340,7 @@ static string GetBashFromPath() {
     start = end + 1;
   } while (true);
 
-  debug_log("bash.exe not found on PATH");
+  debug_log("%s not found on PATH", binary_name.c_str());
   return string();
 }
 
@@ -1355,7 +1355,7 @@ static string LocateBash() {
     return git_on_win_bash;
   }
 
-  return GetBashFromPath();
+  return GetBinaryFromPath("bash.exe");
 }
 
 void DetectBashOrDie() {
@@ -1388,4 +1388,14 @@ void DetectBashOrDie() {
   }
 }
 
+void EnsurePythonPathOption(std::vector<string>* options) {
+  string python_path = GetBinaryFromPath("python.exe");
+  if (!python_path.empty()) {
+    // Provide python path as coming from the least important rc file.
+    std::replace(python_path.begin(), python_path.end(), '\\', '/');
+    options->push_back(string("--default_override=0:build=--python_path=") +
+                       python_path);
+  }
+}
+
 }  // namespace blaze
diff --git a/src/main/cpp/option_processor.cc b/src/main/cpp/option_processor.cc
index 170103c3eb..a7b52d8d83 100644
--- a/src/main/cpp/option_processor.cc
+++ b/src/main/cpp/option_processor.cc
@@ -509,6 +509,8 @@ std::vector<std::string> OptionProcessor::GetBlazercAndEnvCommandArgs(
     "--default_override=0:common=--terminal_columns=" +
         ToString(GetTerminalColumns())};
 
+  EnsurePythonPathOption(&result);
+
   // Push the options mapping .blazerc numbers to filenames.
   for (const RcFile* blazerc : blazercs) {
     result.push_back("--rc_source=" + blaze::ConvertPath(blazerc->Filename()));