[mlir][sparse] Improving error messages for openSparseTensorCOO

[wrengr]

With the previous error message I had some difficulty tracking down a bug, since it only printed "Cannot find (null)" without any stacktrace or other information to go on. Arguably all the other fprintf calls in this function should be updated to give a bit more information too, but I'll leave that for future work.

[aartbik]

mlir/lib/ExecutionEngine/SparseTensorUtils.cpp

666–667

Typo: Received

[wrengr]

pushing the error message beck to the root cause

[wrengr]

Correcting typo

mlir/lib/ExecutionEngine/SparseTensorUtils.cpp

 /// sparse tensor in coordinate scheme.
 template <typename V>
 static SparseTensorCOO<V> *openSparseTensorCOO(char *filename, uint64_t rank,
                                                const uint64_t *sizes,
                                                const uint64_t *perm) {
   // Open the file.
   FILE *file = fopen(filename, "r");
   if (!file) {
-    fprintf(stderr, "Cannot find %s\n", filename);
+    assert(filename && "Received nullptr for filename");
+    fprintf(stderr, "Cannot find file %s\n", filename);
     exit(1);
   }
   // Perform some file format dependent set up.
   char line[kColWidth];
   uint64_t idata[512];
   bool isSymmetric = false;
   if (strstr(filename, ".mtx")) {
     readMMEHeader(file, filename, line, idata, &isSymmetric);

 //===----------------------------------------------------------------------===//
 
 /// Helper method to read a sparse tensor filename from the environment,
 /// defined with the naming convention ${TENSOR0}, ${TENSOR1}, etc.
 char *getTensorFilename(index_type id) {
   char var[80];
   sprintf(var, "TENSOR%" PRIu64, id);
   char *env = getenv(var);
+  if (!env) {
+    fprintf(stderr, "Environment variable %s is not set\n", var);
+    exit(1);
+  }
   return env;
 }
 
 /// Returns size of sparse tensor in given dimension.
 index_type sparseDimSize(void *tensor, index_type d) {
   return static_cast<SparseTensorStorageBase *>(tensor)->getDimSize(d);
 }