From d3bde99d425778ceb6cf4c10557a2aa4221afff3 Mon Sep 17 00:00:00 2001
From: Gleb Belov <gleb@ampl.com>
Date: Fri, 28 Jul 2023 13:16:59 +1000
Subject: [PATCH] ASL-style 'writeprob=(file).sol' #218

---
 include/mp/backend-std.h                      | 50 +++++++++++++------
 .../categorized/fast/suf_std/modellist.json   | 11 +++-
 2 files changed, 46 insertions(+), 15 deletions(-)

diff --git a/include/mp/backend-std.h b/include/mp/backend-std.h
index 2ee5dd6dd..1d030f03b 100644
--- a/include/mp/backend-std.h
+++ b/include/mp/backend-std.h
@@ -181,6 +181,13 @@ class StdBackend :
   ALLOW_STD_FEATURE(WRITE_PROBLEM, false)
   FEATURE_API_TO_IMPLEMENT(WRITE_PROBLEM,
                            void DoWriteProblem(const std::string& ))
+      /// Redefine this if you want some extensions
+      /// to be written after solving instead.
+      /// This is for compatibility wiht ASL drivers
+      /// where 'writeprob' was used for native-format model
+      /// and solution output #218.
+      virtual std::set<std::string> NativeResultExtensions() const
+  { return {".sol", ".ilp", ".mst", ".hnt", ".bas", ".json"}; }
 
       /**
       * Solution export.
@@ -949,21 +956,36 @@ class StdBackend :
   /// Write model
   virtual void ExportModel(
         const std::vector<std::string>& filenames) {
+    auto resext = NativeResultExtensions();
     for (const auto& fln: filenames) {
-      try {
-        DoWriteProblem(fln);
-      } catch (const std::exception& exc) {
-        auto msg
-            = std::string("Model export to file '")
-            + fln
-            + "' failed:\n"
-            + exc.what();
-        if (IMPL_HAS_STD_FEATURE(WRITE_SOLUTION))
-          msg +=
-              "\n    Note: to export solutions and results\n"
-              "    in the solver's native formats,\n"
-              "    use option 'tech:writesolution'";
-        MP_RAISE(msg);
+      bool fPostpone = false;
+      if (IMPL_HAS_STD_FEATURE(WRITE_SOLUTION)) {
+        auto dot = fln.rfind('.');  // Postpone this file?
+        if (std::string::npos != dot) {
+          auto ext = fln.substr(dot, fln.size()-dot);
+          if (resext.end() != resext.find(ext)) {
+            fPostpone = true;
+          }
+        }
+      }
+      if (fPostpone) {   // ASL-style usage of 'writeprob' #218
+        storedOptions_.export_sol_files_.push_back(fln);
+      } else {
+        try {
+          DoWriteProblem(fln);
+        } catch (const std::exception& exc) {
+          auto msg
+              = std::string("Model export to file '")
+              + fln
+              + "' failed:\n"
+              + exc.what();
+          if (IMPL_HAS_STD_FEATURE(WRITE_SOLUTION))
+            msg +=
+                "\n    Note: to export solutions and results\n"
+                "    in the solver's native formats,\n"
+                "    use option 'tech:writesolution'";
+          MP_RAISE(msg);
+        }
       }
     }
   }
diff --git a/test/end2end/cases/categorized/fast/suf_std/modellist.json b/test/end2end/cases/categorized/fast/suf_std/modellist.json
index 12ae135eb..ee13ebdec 100644
--- a/test/end2end/cases/categorized/fast/suf_std/modellist.json
+++ b/test/end2end/cases/categorized/fast/suf_std/modellist.json
@@ -49,8 +49,17 @@
     "files" : ["diet.mod", "diet.dat"],
     "options": {
       "ANYSOLVER_options": "writesol=diet.sol"
+    }
+  },
+  {
+    "name" : "diet writeprob=diet.sol",
+    "objective" : 88.2,
+    "tags" : ["linear", "continuous", "writelp", "writesol"],
+    "files" : ["diet.mod", "diet.dat"],
+    "options": {
+      "ANYSOLVER_options": "writeprob=diet.sol"
     },
-    "comment": "Testing quoted string options"
+    "comment": "Test that writing of .sol is delayed #218"
   },
   {
     "name" : "diet duals; var/con sstatus",