Make item crafting options include recipes from nearby books

src/item.cpp

@@ -3295,39 +3295,41 @@ void item::final_info( std::vector<iteminfo> &info, const iteminfo_query *parts,
     }
 
     // list recipes you could use it in
-    itype_id tid;
-    if( contents.empty() ) { // use this item
-        tid = typeId();
-    } else { // use the contained item
-        tid = contents.front().typeId();
-    }
-    const std::set<const recipe *> &known_recipes = g->u.get_learned_recipes().of_component( tid );
-    if( !known_recipes.empty() && parts->test( iteminfo_parts::DESCRIPTION_APPLICABLE_RECIPES ) ) {
-        const inventory &inv = g->u.crafting_inventory();
+    if( parts->test( iteminfo_parts::DESCRIPTION_APPLICABLE_RECIPES ) ) {
+        itype_id tid = contents.empty() ? typeId() : contents.front().typeId();
+        const inventory &crafting_inv = g->u.crafting_inventory();
+        const recipe_subset available_recipe_subset = g->u.get_available_recipes( crafting_inv );
+        const std::set<const recipe *> &item_recipes = available_recipe_subset.of_component( tid );
 
-        if( known_recipes.size() > 24 ) {
-            insert_separation_line( info );
-            info.push_back( iteminfo( "DESCRIPTION",
-                                      _( "You know dozens of things you could craft with it." ) ) );
-        } else if( known_recipes.size() > 12 ) {
+        if( item_recipes.empty() ) {
             insert_separation_line( info );
             info.push_back( iteminfo( "DESCRIPTION",
-                                      _( "You could use it to craft various other things." ) ) );
+                                      _( "You know of nothing you could craft with it." ) ) );
         } else {
-            const std::string recipes = enumerate_as_string( known_recipes.begin(), known_recipes.end(),
-            [ &inv ]( const recipe * r ) {
-                if( r->deduped_requirements().can_make_with_inventory(
-                        inv, r->get_component_filter() ) ) {
-                    return r->result_name();
-                } else {
-                    return string_format( "<dark>%s</dark>", r->result_name() );
-                }
-            } );
-            if( !recipes.empty() ) {
+            if( item_recipes.size() > 24 ) {
+                insert_separation_line( info );
+                info.push_back( iteminfo( "DESCRIPTION",
+                                          _( "You know dozens of things you could craft with it." ) ) );
+            } else if( item_recipes.size() > 12 ) {
                 insert_separation_line( info );
                 info.push_back( iteminfo( "DESCRIPTION",
-                                          string_format( _( "You could use it to craft: %s" ),
-                                                  recipes ) ) );
+                                          _( "You could use it to craft various other things." ) ) );
+            } else {
+                const std::string recipes = enumerate_as_string( item_recipes.begin(), item_recipes.end(),
+                [ &crafting_inv ]( const recipe * r ) {
+                    if( r->deduped_requirements().can_make_with_inventory(
+                            crafting_inv, r->get_component_filter() ) ) {
+                        return r->result_name();
+                    } else {
+                        return string_format( "<dark>%s</dark>", r->result_name() );
+                    }
+                } );
+                if( !recipes.empty() ) {
+                    insert_separation_line( info );
+                    info.push_back( iteminfo( "DESCRIPTION",
+                                              string_format( _( "You could use it to craft: %s" ),
+                                                      recipes ) ) );
+                }
             }
         }
     }

tests/iteminfo_test.cpp

@@ -7,6 +7,7 @@
 #include "game.h"
 #include "item.h"
 #include "iteminfo_query.h"
+#include "recipe_dictionary.h"
 
 static void iteminfo_test( const item &i, const iteminfo_query &q, const std::string &reference )
 {
@@ -99,3 +100,58 @@ TEST_CASE( "nutrient_ranges_for_recipe_exemplars", "[item][iteminfo]" )
         "Vitamins (RDA): Calcium (7-28%), Iron (0-83%), "
         "Vitamin A (3-11%), Vitamin B12 (2-6%), and Vitamin C (1-85%)\n" );
 }
+
+TEST_CASE( "show available recipes with item as an ingredient", "[item][iteminfo][recipes]" )
+{
+    iteminfo_query q( { iteminfo_parts::DESCRIPTION_APPLICABLE_RECIPES } );
+    const recipe *purtab = &recipe_id( "pur_tablets" ).obj();
+    g->u.empty_traits();
+
+    GIVEN( "character has a potassium iodide tablet and no skill" ) {
+        item &iodine = g->u.i_add( item( "iodine" ) );
+        g->u.empty_skills();
+
+        THEN( "nothing is craftable from it" ) {
+            iteminfo_test(
+                iodine, q,
+                "--\nYou know of nothing you could craft with it.\n" );
+        }
+
+        WHEN( "they acquire the needed skills" ) {
+            g->u.set_skill_level( purtab->skill_used, purtab->difficulty );
+            REQUIRE( g->u.get_skill_level( purtab->skill_used ) == purtab->difficulty );
+
+            THEN( "still nothing is craftable from it" ) {
+                iteminfo_test(
+                    iodine, q,
+                    "--\nYou know of nothing you could craft with it.\n" );
+            }
+
+            WHEN( "they have no book, but have the recipe memorized" ) {
+                g->u.learn_recipe( purtab );
+                REQUIRE( g->u.knows_recipe( purtab ) );
+
+                THEN( "they can use potassium iodide tablets to craft it" ) {
+                    iteminfo_test(
+                        iodine, q,
+                        "--\n"
+                        "You could use it to craft: "
+                        "<color_c_dark_gray>water purification tablet</color>\n" );
+                }
+            }
+
+            WHEN( "they have the recipe in a book, but not memorized" ) {
+                g->u.i_add( item( "textbook_chemistry" ) );
+
+                THEN( "they can use potassium iodide tablets to craft it" ) {
+                    iteminfo_test(
+                        iodine, q,
+                        "--\n"
+                        "You could use it to craft: "
+                        "<color_c_dark_gray>water purification tablet</color>\n" );
+                }
+            }
+        }
+    }
+}
+