xtensor: Make HighFive compatible with 0.26.

XTensor reorganized its headers in 0.26. This commit introduces come
logic to guess the correct path: if the compiler is C++17 or later, use
`__has_include` to check both locations; otherwise it must be an xtensor
version prior to 0.26, because 0.26 onwards require a C++17 compiler.

Author: 1uc

README.md

@@ -214,6 +214,12 @@ HighFive integrates with the following libraries:
 - xtensor (optional)
 - half (optional)
 
+#### XTensor Header Location
+XTensor reorganized their headers in version 0.26. HighFive attempts to guess
+where the headers can be found. The guessing can be overridded by setting
+`HIGHFIVE_XTENSOR_HEADER_VERSION` to: `1` for finding `xtensor.hpp` in
+`<xtensor/xtensor.hpp>` and `2` for `<xtensor/containers/xtensor.hpp>`.
+
 ## Versioning & Code Stability
 We use semantic versioning. Currently, we're preparing `v3` which contains a
 limited set of breaking changes required to eliminate undesireable behaviour or

include/highfive/H5Easy.hpp

@@ -28,8 +28,6 @@
 #endif
 
 #ifdef H5_USE_XTENSOR
-#include <xtensor/xarray.hpp>
-#include <xtensor/xtensor.hpp>
 #include "xtensor.hpp"
 #endif
 

include/highfive/bits/xtensor_header_version.hpp

@@ -0,0 +1,12 @@
+#ifndef HIGHFIVE_XTENSOR_HEADER_VERSION
+#if __cplusplus >= 201703L
+#if __has_include(<xtensor/xtensor.hpp>)
+#define HIGHFIVE_XTENSOR_HEADER_VERSION 1
+#elif __has_include(<xtensor/container/xtensor.hpp>)
+#define HIGHFIVE_XTENSOR_HEADER_VERSION 2
+#endif
+#else
+#define HIGHFIVE_XTENSOR_HEADER_VERSION 1
+#endif
+#endif
+

include/highfive/xtensor.hpp

@@ -2,10 +2,19 @@
 
 #include "bits/H5Inspector_decl.hpp"
 #include "H5Exception.hpp"
+#include "bits/xtensor_header_version.hpp"
 
+#if HIGHFIVE_XTENSOR_HEADER_VERSION == 1
 #include <xtensor/xtensor.hpp>
 #include <xtensor/xarray.hpp>
 #include <xtensor/xadapt.hpp>
+#elif HIGHFIVE_XTENSOR_HEADER_VERSION == 2
+#include <xtensor/container/xtensor.hpp>
+#include <xtensor/container/xarray.hpp>
+#include <xtensor/container/xadapt.hpp>
+#else
+#error "Set HIGHFIVE_XTENSOR_HEADER_VERSION to `1` for pre 0.26; `2` otherwise."
+#endif
 
 namespace HighFive {
 namespace details {

src/examples/easy_attribute.cpp

@@ -13,7 +13,14 @@
 
 // optionally enable plug-in xtensor
 #ifdef H5_USE_XTENSOR
+#include "bits/xtensor_header_version.hpp"
+#if HIGHFIVE_XTENSOR_HEADER_VERSION == 1
 #include <xtensor/xtensor.hpp>
+#elif HIGHFIVE_XTENSOR_HEADER_VERSION == 2
+#include <xtensor/container/xtensor.hpp>
+#else
+#error "Failed to detect HIGHFIVE_XTENSOR_HEADER_VERSION."
+#endif
 #endif
 
 // optionally enable plug-in Eigen

src/examples/easy_dumpoptions.cpp

@@ -13,7 +13,14 @@
 
 // optionally enable plug-in xtensor
 #ifdef H5_USE_XTENSOR
+#include <highfive/bits/xtensor_header_version.hpp>
+#if HIGHFIVE_XTENSOR_HEADER_VERSION == 1
 #include <xtensor/xtensor.hpp>
+#elif HIGHFIVE_XTENSOR_HEADER_VERSION == 2
+#include <xtensor/container/xtensor.hpp>
+#else
+#error "Failed to detect HIGHFIVE_XTENSOR_HEADER_VERSION."
+#endif
 #endif
 
 // optionally enable plug-in Eigen

src/examples/easy_load_dump.cpp

@@ -13,7 +13,14 @@
 
 // optionally enable plug-in xtensor
 #ifdef H5_USE_XTENSOR
+#include <highfive/bits/xtensor_header_version.hpp>
+#if HIGHFIVE_XTENSOR_HEADER_VERSION == 1
 #include <xtensor/xtensor.hpp>
+#elif HIGHFIVE_XTENSOR_HEADER_VERSION == 2
+#include <xtensor/container/xtensor.hpp>
+#else
+#error "Failed to detect HIGHFIVE_XTENSOR_HEADER_VERSION."
+#endif
 #endif
 
 // optionally enable plug-in Eigen

tests/unit/test_xtensor.cpp

@@ -13,10 +13,19 @@
 #include <catch2/catch_template_test_macros.hpp>
 
 #include <highfive/highfive.hpp>
+#include <highfive/xtensor.hpp>
+
+#if HIGHFIVE_XTENSOR_HEADER_VERSION == 1
 #include <xtensor/xtensor.hpp>
 #include <xtensor/xview.hpp>
 #include <xtensor/xio.hpp>
-#include <highfive/xtensor.hpp>
+#elif HIGHFIVE_XTENSOR_HEADER_VERSION == 2
+#include <xtensor/container/xtensor.hpp>
+#include <xtensor/views/xview.hpp>
+#include <xtensor/io/xio.hpp>
+#else
+#error "Failed to detect HIGHFIVE_XTENSOR_HEADER_VERSION."
+#endif
 
 #include "data_generator.hpp"
 

tests/unit/tests_high_five_easy.cpp

@@ -22,8 +22,16 @@
 
 
 #ifdef HIGHFIVE_TEST_XTENSOR
+#include <highfive/bits/xtensor_header_version.hpp>
+#if HIGHFIVE_XTENSOR_HEADER_VERSION == 1
 #include <xtensor/xrandom.hpp>
 #include <xtensor/xview.hpp>
+#elif HIGHFIVE_XTENSOR_HEADER_VERSION == 2
+#include <xtensor/generators/xrandom.hpp>
+#include <xtensor/views/xview.hpp>
+#else
+#error "Failed to detect HIGHFIVE_XTENSOR_HEADER_VERSION."
+#endif
 #endif
 
 #ifdef HIGHFIVE_TEST_EIGEN