support backslash directory separator on WIN32

Makefile

@@ -54,6 +54,7 @@ LIB_SRC = \
 	core/libjsonnet.cpp \
 	core/parser.cpp \
 	core/pass.cpp \
+	core/path_utils.cpp \
 	core/static_analysis.cpp \
 	core/string_utils.cpp \
 	core/vm.cpp \

core/BUILD

@@ -9,6 +9,7 @@ cc_library(
         "libjsonnet.cpp",
         "parser.cpp",
         "pass.cpp",
+        "path_utils.cpp",
         "static_analysis.cpp",
         "string_utils.cpp",
         "vm.cpp",
@@ -21,6 +22,7 @@ cc_library(
         "lexer.h",
         "parser.h",
         "pass.h",
+        "path_utils.h",
         "state.h",
         "static_analysis.h",
         "static_error.h",

core/CMakeLists.txt

@@ -10,6 +10,7 @@ set(LIBJSONNET_HEADERS
     ../include/libjsonnet_fmt.h
     parser.h
     pass.h
+    path_utils.h
     state.h
     static_analysis.h
     static_error.h
@@ -24,6 +25,7 @@ set(LIBJSONNET_SOURCE
     libjsonnet.cpp
     parser.cpp
     pass.cpp
+    path_utils.cpp
     static_analysis.cpp
     string_utils.cpp
     vm.cpp)

core/path_utils.cpp

@@ -0,0 +1,39 @@
+/*
+Copyright 2024 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+#include "path_utils.h"
+#include <string>
+
+namespace jsonnet::internal {
+
+// C++17 adds <filesystem>
+// We could consider using that instead.
+
+#if _WIN32
+static const char DIR_SEPARATORS[] = "\\/";
+#else
+static const char DIR_SEPARATORS[] = "/";
+#endif
+
+std::string path_dir_with_trailing_separator(const std::string &path) {
+    size_t last_slash = path.find_last_of(DIR_SEPARATORS);
+    if (last_slash != std::string::npos) {
+        return path.substr(0, last_slash + 1);
+    }
+    return "";
+}
+
+}  // namespace jsonnet::internal

core/path_utils.h

@@ -0,0 +1,34 @@
+/*
+Copyright 2024 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+#ifndef JSONNET_PATH_UTILS_H
+#define JSONNET_PATH_UTILS_H
+
+#include <string>
+
+namespace jsonnet::internal {
+
+/** Get everything except the filename from a path. If the path is just a filename, returns "".
+ *
+ * The result includes the trailing directory separator (if there is one in the input).
+ * Exact behaviour is platform-specific (different platforms use different directory separators).
+ */
+std::string path_dir_with_trailing_separator(const std::string &path);
+
+}  // namespace jsonnet::internal
+
+#endif
+

core/vm.cpp

@@ -35,6 +35,7 @@ limitations under the License.
 #include "static_analysis.h"
 #include "string_utils.h"
 #include "vm.h"
+#include "path_utils.h"
 
 namespace jsonnet::internal {
 
@@ -54,17 +55,6 @@ using json = nlohmann::json;
 
 namespace {
 
-/** Turn a path e.g. "/a/b/c" into a dir, e.g. "/a/b/".  If there is no path returns "".
- */
-std::string dir_name(const std::string &path)
-{
-    size_t last_slash = path.rfind('/');
-    if (last_slash != std::string::npos) {
-        return path.substr(0, last_slash + 1);
-    }
-    return "";
-}
-
 /** Stack frames.
  *
  * Of these, FRAME_CALL is the most special, as it is the only frame the stack
@@ -800,7 +790,11 @@ class Interpreter {
      */
     ImportCacheValue *importData(const LocationRange &loc, const LiteralString *file)
     {
-        std::string dir = dir_name(loc.file);
+        // `dir` is passed to the importCallback, which may be externally defined.
+        // For backwards compatibility, we need to keep the trailing directory separator.
+        // For example, the default callback in libjsonnet.cpp joins paths with simple
+        // string concatenation. Other (external) implementations might do the same.
+        std::string dir = path_dir_with_trailing_separator(loc.file);
 
         const UString &path = file->value;
 

setup.py

@@ -27,6 +27,7 @@
     "core/lexer.cpp",
     "core/parser.cpp",
     "core/pass.cpp",
+    "core/path_utils.cpp",
     "core/static_analysis.cpp",
     "core/string_utils.cpp",
     "core/vm.cpp",