Add --omit-drop and --omit-create options

4 files changed, 140 insertions, 76 deletions

diff --git a/NEWS b/NEWS
index 475765d..8502a73 100644
--- a/NEWS
+++ b/NEWS
@@ -85,6 +85,9 @@ Version 2.1.0
    of custom SQL between the DROP and CREATE statements in the generated
    database schema file.
 
+ * New options, --omit-drop and --omit-create, trigger the omission of DROP
+   and CREATE statements, respectively, from the generated database schema.
+
  * New ODB manual section, 6.3 "Circular Relationships", explains how to
    handle persistent classes with circular dependencies that are defined
    in separate headers.
diff --git a/odb/generator.cxx b/odb/generator.cxx
index 8b03006..d4e1505 100644
--- a/odb/generator.cxx
+++ b/odb/generator.cxx
@@ -284,12 +284,15 @@ generate (options const& ops,
 
       // Copy prologue.
       //
-      hxx << "// Begin prologue." << endl
-          << "//" << endl;
-      append (hxx, ops.hxx_prologue (), ops.hxx_prologue_file ());
-      hxx << "//" << endl
-          << "// End prologue." << endl
-          << endl;
+      if (!ops.hxx_prologue ().empty () || !ops.hxx_prologue_file ().empty ())
+      {
+        hxx << "// Begin prologue." << endl
+            << "//" << endl;
+        append (hxx, ops.hxx_prologue (), ops.hxx_prologue_file ());
+        hxx << "//" << endl
+            << "// End prologue." << endl
+            << endl;
+      }
 
       // Include main file(s).
       //
@@ -331,12 +334,15 @@ generate (options const& ops,
 
       // Copy epilogue.
       //
-      hxx << "// Begin epilogue." << endl
-          << "//" << endl;
-      append (hxx, ops.hxx_epilogue (), ops.hxx_epilogue_file ());
-      hxx << "//" << endl
-          << "// End epilogue." << endl
-          << endl;
+      if (!ops.hxx_epilogue ().empty () || !ops.hxx_epilogue_file ().empty ())
+      {
+        hxx << "// Begin epilogue." << endl
+            << "//" << endl;
+        append (hxx, ops.hxx_epilogue (), ops.hxx_epilogue_file ());
+        hxx << "//" << endl
+            << "// End epilogue." << endl
+            << endl;
+      }
 
       hxx << "#include <odb/post.hxx>" << endl
           << endl;
@@ -360,12 +366,15 @@ generate (options const& ops,
 
       // Copy prologue.
       //
-      ixx << "// Begin prologue." << endl
-          << "//" << endl;
-      append (ixx, ops.ixx_prologue (), ops.ixx_prologue_file ());
-      ixx << "//" << endl
-          << "// End prologue." << endl
-          << endl;
+      if (!ops.ixx_prologue ().empty () || !ops.ixx_prologue_file ().empty ())
+      {
+        ixx << "// Begin prologue." << endl
+            << "//" << endl;
+        append (ixx, ops.ixx_prologue (), ops.ixx_prologue_file ());
+        ixx << "//" << endl
+            << "// End prologue." << endl
+            << endl;
+      }
 
       {
         // We don't want to indent prologues/epilogues.
@@ -390,11 +399,14 @@ generate (options const& ops,
 
       // Copy epilogue.
       //
-      ixx << "// Begin epilogue." << endl
-          << "//" << endl;
-      append (ixx, ops.ixx_epilogue (), ops.ixx_epilogue_file ());
-      ixx << "//" << endl
-          << "// End epilogue." << endl;
+      if (!ops.ixx_epilogue ().empty () || !ops.ixx_epilogue_file ().empty ())
+      {
+        ixx << "// Begin epilogue." << endl
+            << "//" << endl;
+        append (ixx, ops.ixx_epilogue (), ops.ixx_epilogue_file ());
+        ixx << "//" << endl
+            << "// End epilogue." << endl;
+      }
 
       if (ops.show_sloc ())
         cerr << ixx_name << ": " << sloc.stream ().count () << endl;
@@ -416,12 +428,15 @@ generate (options const& ops,
 
       // Copy prologue.
       //
-      cxx << "// Begin prologue." << endl
-          << "//" << endl;
-      append (cxx, ops.cxx_prologue (), ops.cxx_prologue_file ());
-      cxx << "//" << endl
-          << "// End prologue." << endl
-          << endl;
+      if (!ops.cxx_prologue ().empty () || !ops.cxx_prologue_file ().empty ())
+      {
+        cxx << "// Begin prologue." << endl
+            << "//" << endl;
+        append (cxx, ops.cxx_prologue (), ops.cxx_prologue_file ());
+        cxx << "//" << endl
+            << "// End prologue." << endl
+            << endl;
+      }
 
       cxx << "#include " << ctx->process_include_path (hxx_name) << endl
           << endl;
@@ -453,12 +468,15 @@ generate (options const& ops,
 
       // Copy epilogue.
       //
-      cxx << "// Begin epilogue." << endl
-          << "//" << endl;
-      append (cxx, ops.cxx_epilogue (), ops.cxx_epilogue_file ());
-      cxx << "//" << endl
-          << "// End epilogue." << endl
-          << endl;
+      if (!ops.cxx_epilogue ().empty () || !ops.cxx_epilogue_file ().empty ())
+      {
+        cxx << "// Begin epilogue." << endl
+            << "//" << endl;
+        append (cxx, ops.cxx_epilogue (), ops.cxx_epilogue_file ());
+        cxx << "//" << endl
+            << "// End epilogue." << endl
+            << endl;
+      }
 
       cxx << "#include <odb/post.hxx>" << endl;
 
@@ -477,19 +495,21 @@ generate (options const& ops,
 
       sloc_filter sloc (ctx->os);
 
-      // Copy prologue.
-      //
       sch << "#include <odb/pre.hxx>" << endl
           << endl;
 
       // Copy prologue.
       //
-      sch << "// Begin prologue." << endl
-          << "//" << endl;
-      append (sch, ops.schema_prologue (), ops.schema_prologue_file ());
-      sch << "//" << endl
-          << "// End prologue." << endl
-          << endl;
+      if (!ops.schema_prologue ().empty () ||
+          !ops.schema_prologue_file ().empty ())
+      {
+        sch << "// Begin prologue." << endl
+            << "//" << endl;
+        append (sch, ops.schema_prologue (), ops.schema_prologue_file ());
+        sch << "//" << endl
+            << "// End prologue." << endl
+            << endl;
+      }
 
       sch << "#include " << ctx->process_include_path (hxx_name) << endl
           << endl;
@@ -515,12 +535,16 @@ generate (options const& ops,
 
       // Copy epilogue.
       //
-      sch << "// Begin epilogue." << endl
-          << "//" << endl;
-      append (sch, ops.schema_epilogue (), ops.schema_epilogue_file ());
-      sch << "//" << endl
-          << "// End epilogue." << endl
-          << endl;
+      if (!ops.schema_epilogue ().empty () ||
+          !ops.schema_epilogue_file ().empty ())
+      {
+        sch << "// Begin epilogue." << endl
+            << "//" << endl;
+        append (sch, ops.schema_epilogue (), ops.schema_epilogue_file ());
+        sch << "//" << endl
+            << "// End epilogue." << endl
+            << endl;
+      }
 
       sch << "#include <odb/post.hxx>" << endl;
 
@@ -547,30 +571,50 @@ generate (options const& ops,
         {
           relational::schema::generate_prologue ();
 
-          sql << "/* Begin prologue." << endl
-              << " */" << endl;
-          append (sql, ops.sql_prologue (), ops.sql_prologue_file ());
-          sql << "/*" << endl
-              << " * End prologue. */" << endl
-              << endl;
-
-          relational::schema::generate_drop ();
-
-          sql << "/* Begin interlude." << endl
-              << " */" << endl;
-          append (sql, ops.sql_interlude (), ops.sql_interlude_file ());
-          sql << "/*" << endl
-              << " * End interlude. */" << endl
-              << endl;
-
-          relational::schema::generate_create ();
-
-          sql << "/* Begin epilogue." << endl
-              << " */" << endl;
-          append (sql, ops.sql_epilogue (), ops.sql_epilogue_file ());
-          sql << "/*" << endl
-              << " * End epilogue. */" << endl
-              << endl;
+          // Copy prologue.
+          //
+          if (!ops.sql_prologue ().empty () ||
+              !ops.sql_prologue_file ().empty ())
+          {
+            sql << "/* Begin prologue." << endl
+                << " */" << endl;
+            append (sql, ops.sql_prologue (), ops.sql_prologue_file ());
+            sql << "/*" << endl
+                << " * End prologue. */" << endl
+                << endl;
+          }
+
+          if (!ops.omit_drop ())
+            relational::schema::generate_drop ();
+
+          // Copy interlude.
+          //
+          if (!ops.sql_interlude ().empty () ||
+              !ops.sql_interlude_file ().empty ())
+          {
+            sql << "/* Begin interlude." << endl
+                << " */" << endl;
+            append (sql, ops.sql_interlude (), ops.sql_interlude_file ());
+            sql << "/*" << endl
+                << " * End interlude. */" << endl
+                << endl;
+          }
+
+          if (!ops.omit_create ())
+            relational::schema::generate_create ();
+
+          // Copy epilogue.
+          //
+          if (!ops.sql_epilogue ().empty () ||
+              !ops.sql_epilogue_file ().empty ())
+          {
+            sql << "/* Begin epilogue." << endl
+                << " */" << endl;
+            append (sql, ops.sql_epilogue (), ops.sql_epilogue_file ());
+            sql << "/*" << endl
+                << " * End epilogue. */" << endl
+                << endl;
+          }
 
           relational::schema::generate_epilogue ();
           break;
diff --git a/odb/options.cli b/odb/options.cli
index 6740572..f61aa0e 100644
--- a/odb/options.cli
+++ b/odb/options.cli
@@ -102,6 +102,16 @@ class options
      formats."
   };
 
+  bool --omit-drop
+  {
+    "Omit \cb{DROP} statements from the generated database schema."
+  };
+
+  bool --omit-create
+  {
+    "Omit \cb{CREATE} statements from the generated database schema."
+  };
+
   std::string --schema-name = ""
   {
     "<name>",
diff --git a/odb/relational/schema.hxx b/odb/relational/schema.hxx
index e6d4824..56857f3 100644
--- a/odb/relational/schema.hxx
+++ b/odb/relational/schema.hxx
@@ -797,7 +797,7 @@ namespace relational
       post ()
       {
         if (!first_) // Ignore empty statements.
-          os << strlit (line_) << ");" << endl;
+          os << strlit (line_) << ");";
       }
 
     private:
@@ -873,10 +873,12 @@ namespace relational
            << "{"
            << "ODB_POTENTIALLY_UNUSED (db);"
            << "ODB_POTENTIALLY_UNUSED (pass);"
+           << "ODB_POTENTIALLY_UNUSED (drop);"
            << endl;
 
         // Drop.
         //
+        if (!options.omit_drop ())
         {
           bool close (false);
 
@@ -904,11 +906,16 @@ namespace relational
 
         // Create.
         //
+        if (!options.omit_create ())
         {
           bool close (false);
 
-          os << "else"
-             << "{";
+          if (options.omit_drop ())
+            os << "if (!drop)";
+          else
+            os << "else";
+
+          os << "{";
 
           for (unsigned short pass (1); pass < 3; ++pass)
           {