instrumentation: Null unknown static system info

Add tests to ensure the `staticSystemInformation` subfields are always
either filled with meaningful data of a given type (i.e., non-empty
string, or >0 integer), or `null` if the data cannot be determined.

Issue: #27537, #27545

Help/manual/cmake-instrumentation.7.rst

@@ -503,7 +503,9 @@ generated whenever `Indexing`_ occurs and deleted after any user-specified
 
 ``staticSystemInformation``
   Specifies the static information collected about the host machine
-  CMake is being run from. Only included when enabled by the `v1 Query Files`_.
+  CMake is being run from. If CMake is unable to determine the value of any
+  given field, it will be ``null``. Only included when enabled by the
+  `v1 Query Files`_.
 
   * ``OSName``
   * ``OSPlatform``

Source/cmInstrumentation.cxx

@@ -492,6 +492,14 @@ void cmInstrumentation::InsertStaticSystemInformation(Json::Value& root)
     static_cast<Json::Value::UInt64>(info.GetTotalVirtualMemory());
   infoRoot["vendorID"] = info.GetVendorID();
   infoRoot["vendorString"] = info.GetVendorString();
+
+  // Record fields unable to be determined as null JSON objects.
+  for (std::string const& field : infoRoot.getMemberNames()) {
+    if ((infoRoot[field].isNumeric() && infoRoot[field].asInt64() <= 0) ||
+        (infoRoot[field].isString() && infoRoot[field].asString().empty())) {
+      infoRoot[field] = Json::nullValue;
+    }
+  }
   root["staticSystemInformation"] = infoRoot;
 }
 

Tests/RunCMake/Instrumentation/hook.cmake

@@ -108,6 +108,53 @@ if (NOT hasStaticInfo STREQUAL UNEXPECTED)
   json_has_key("${index}" "${staticSystemInformation}" totalVirtualMemory ${hasStaticInfo})
   json_has_key("${index}" "${staticSystemInformation}" vendorID ${hasStaticInfo})
   json_has_key("${index}" "${staticSystemInformation}" vendorString ${hasStaticInfo})
+
+  # FIXME(#27545): We currently do not guarantee that the fields above which
+  # output strings are non-empty. `vendorString` and `processorName` especially
+  # have shown issues on some platforms. This test is logically equivalent to
+  # RunCMake.cmake_host_system_information, which uses the same underlying
+  # implementation.
+  set(string_fields
+    OSName
+    OSPlatform
+    OSRelease
+    OSVersion
+    familyId
+    hostname
+    modelId
+    vendorID
+    vendorString
+  )
+  foreach (field IN LISTS string_fields)
+    string(JSON ${field}_type TYPE "${staticSystemInformation}" ${field})
+    if (NOT "${${field}_type}" STREQUAL "NULL" AND NOT "${${field}_type}" STREQUAL "STRING")
+      add_error("Got bad type '${${field}_type}' for field '${field}': ${${field}}")
+    endif()
+    if ("${${field}_type}" STREQUAL "STRING" AND ${field} STREQUAL "")
+      add_error("Got empty string for field '${field}'")
+    endif()
+  endforeach()
+
+  # We guarantee that the numeric fields are either indeed numeric, or else
+  # null.
+  set(numeric_fields
+    numberOfLogicalCPU
+    numberOfPhysicalCPU
+    processorAPICID
+    processorCacheSize
+    processorClockFrequency
+    totalPhysicalMemory
+    totalVirtualMemory
+  )
+  foreach (field IN LISTS numeric_fields)
+    string(JSON ${field}_type TYPE "${staticSystemInformation}" ${field})
+    if (NOT "${${field}_type}" STREQUAL "NULL" AND NOT "${${field}_type}" STREQUAL "NUMBER")
+      add_error("Got bad type '${${field}_type}' for field '${field}': ${${field}}")
+    endif()
+    if ("${${field}_type}" STREQUAL "NUMBER" AND ${field} LESS_EQUAL 0)
+      add_error("Got bad value for field '${field}': ${${field}}")
+    endif()
+  endforeach()
 endif()
 
 get_filename_component(v1 ${dataDir} DIRECTORY)

Tests/RunCMake/Instrumentation/json.cmake

@@ -41,6 +41,7 @@ function(json_missing_key file json key)
 endfunction()
 
 # Check if the JSON string `json` has `key` and its value matches `expected`.
+# If successful, return its value in `key`.
 function(json_assert_key file json key expected)
   string(JSON data ERROR_VARIABLE missingKey GET "${json}" ${key})
   if (NOT missingKey MATCHES NOTFOUND)
@@ -52,6 +53,7 @@ function(json_assert_key file json key expected)
       "Unexpected data in custom content file:\nGot ${data}, Expected ${expected}."
     )
   endif()
+  set(${key} ${data} PARENT_SCOPE)
   return(PROPAGATE RunCMake_TEST_FAILED ERROR_MESSAGE)
 endfunction()