Applied fix of 2316, but exposed isssue 2318

Author: jajhall

FEATURES.md

@@ -20,3 +20,7 @@ Added `Highs_changeRowsBoundsByRange` to C API, fixing [#2296](https://github.co
 
 Corrected docstrings for `Highs_getReducedRow`, motivated by [#2312](https://github.com/ERGO-Code/HiGHS/issues/2312))
 
+LP file reader no longer fails when there is no objective section. Fix is [#2316](https://github.com/ERGO-Code/HiGHS/pull/2316)), but this exposes code quality issue [#2318](https://github.com/ERGO-Code/HiGHS/issues/2318))
+
+
+

check/TestFilereader.cpp

@@ -98,10 +98,18 @@ TEST_CASE("filereader-edge-cases", "[highs_filereader]") {
     }
 
     if (test_garbage_lp) {
+      // Since #2316, reading an LP file of garbage yields an empty
+      // model, since the absence of an objecive is (rightly) no
+      // longer an error. However the LP file reader should fail due
+      // to the requirement that a LP format file must begin with a
+      // keyword.
       if (dev_run) printf("\ngarbage.lp\n");
       model_file = std::string(HIGHS_DIR) + "/check/instances/" + model + ".lp";
       read_status = highs.readModel(model_file);
-      REQUIRE(read_status == HighsStatus::kError);
+      REQUIRE(read_status == HighsStatus::kOk);
+      REQUIRE(highs.getLp().num_col_ == 0);
+      REQUIRE(highs.getLp().num_row_ == 0);
+      REQUIRE(highs.getLp().a_matrix_.numNz() == 0);
     }
   }
 

check/instances/garbage.lp

@@ -1,3 +1,4 @@
+Maximize
 \^%(^%(T&*)(lkszdvhfalkmnthry6v54y76m87yq,x,
 dvhfalkmnthry6v54y76m87yq,x,^%(^%(T&*)(lksz
 (T&*)(lkszdvhfalkmnthry6v54y76m87yq,x,^%(^%

extern/filereaderlp/reader.cpp

@@ -308,23 +308,6 @@ Model Reader::read() {
   splittokens();
 
   // std::clog << "Setting up model..." << std::endl;
-  //
-  // Since
-  //
-  // "The problem statement must begin with the word MINIMIZE or
-  // MAXIMIZE, MINIMUM or MAXIMUM, or the abbreviations MIN or MAX, in
-  // any combination of upper- and lower-case characters. The word
-  // introduces the objective function section."
-  //
-  // Use positivity of sectiontokens.count(LpSectionKeyword::OBJMIN) +
-  // sectiontokens.count(LpSectionKeyword::OBJMAX) to identify garbage file
-  //
-
-  const int num_objective_section =
-    sectiontokens.count(LpSectionKeyword::OBJMIN) +
-    sectiontokens.count(LpSectionKeyword::OBJMAX);
-  lpassert(num_objective_section>0);
-
   processsections();
   processedtokens.clear();
   processedtokens.shrink_to_fit();