7 files changed, 116 insertions, 0 deletions
diff --git a/source/blender/blenkernel/BKE_fcurve_driver.h b/source/blender/blenkernel/BKE_fcurve_driver.h
index 18676dfcb38..7e4e0ad3c2a 100644
--- a/source/blender/blenkernel/BKE_fcurve_driver.h
+++ b/source/blender/blenkernel/BKE_fcurve_driver.h
@@ -105,6 +105,13 @@ void driver_change_variable_type(struct DriverVar *dvar, int type);
  */
 void driver_variable_name_validate(struct DriverVar *dvar);
 /**
+ * Ensure the driver variable's name is unique.
+ *
+ * Assumes the driver variable has already been assigned to the driver, so that
+ * the prev/next pointers can be used to find the other variables.
+ */
+void driver_variable_unique_name(struct DriverVar *dvar);
+/**
  * Add a new driver variable.
  */
 struct DriverVar *driver_add_new_variable(struct ChannelDriver *driver);
diff --git a/source/blender/blenkernel/intern/fcurve_driver.c b/source/blender/blenkernel/intern/fcurve_driver.c
index 5496519e53b..ce30f80ba65 100644
--- a/source/blender/blenkernel/intern/fcurve_driver.c
+++ b/source/blender/blenkernel/intern/fcurve_driver.c
@@ -29,6 +29,7 @@
 
 #include "BLI_alloca.h"
 #include "BLI_expr_pylike_eval.h"
+#include "BLI_listbase.h"
 #include "BLI_math.h"
 #include "BLI_string_utils.h"
 #include "BLI_threads.h"
@@ -864,6 +865,12 @@ void driver_variable_name_validate(DriverVar *dvar)
   }
 }
 
+void driver_variable_unique_name(DriverVar *dvar)
+{
+  ListBase variables = BLI_listbase_from_link((Link *)dvar);
+  BLI_uniquename(&variables, dvar, dvar->name, '_', offsetof(DriverVar, name), sizeof(dvar->name));
+}
+
 DriverVar *driver_add_new_variable(ChannelDriver *driver)
 {
   DriverVar *dvar;
diff --git a/source/blender/blenlib/BLI_listbase.h b/source/blender/blenlib/BLI_listbase.h
index 7d808d339e9..a2a6e958213 100644
--- a/source/blender/blenlib/BLI_listbase.h
+++ b/source/blender/blenlib/BLI_listbase.h
@@ -46,6 +46,11 @@ int BLI_findstringindex(const struct ListBase *listbase,
                         const char *id,
                         const int offset) ATTR_WARN_UNUSED_RESULT ATTR_NONNULL(1);
 
+/**
+ * Return a ListBase representing the entire list the given Link is in.
+ */
+ListBase BLI_listbase_from_link(struct Link *some_link);
+
 /* Find forwards. */
 
 /**
@@ -279,6 +284,23 @@ BLI_INLINE void BLI_listbase_clear(struct ListBase *lb)
 }
 
 /**
+ * Equality check for ListBase.
+ *
+ * This only shallowly compares the ListBase itself (so the first/last
+ * pointers), and does not do any equality checks on the list items.
+ */
+BLI_INLINE bool BLI_listbase_equal(const struct ListBase *a, const struct ListBase *b)
+{
+  if (a == NULL) {
+    return b == NULL;
+  }
+  if (b == NULL) {
+    return false;
+  }
+  return a->first == b->first && a->last == b->last;
+}
+
+/**
  * Create a generic list node containing link to provided data.
  */
 struct LinkData *BLI_genericNodeN(void *data);
@@ -353,3 +375,10 @@ struct LinkData *BLI_genericNodeN(void *data);
 #ifdef __cplusplus
 }
 #endif
+
+#ifdef __cplusplus
+BLI_INLINE bool operator==(const ListBase &a, const ListBase &b)
+{
+  return BLI_listbase_equal(&a, &b);
+}
+#endif
diff --git a/source/blender/blenlib/intern/listbase.c b/source/blender/blenlib/intern/listbase.c
index a166c846ea7..513b08a589d 100644
--- a/source/blender/blenlib/intern/listbase.c
+++ b/source/blender/blenlib/intern/listbase.c
@@ -749,6 +749,26 @@ int BLI_findstringindex(const ListBase *listbase, const char *id, const int offs
   return -1;
 }
 
+ListBase BLI_listbase_from_link(Link *some_link)
+{
+  ListBase list = {some_link, some_link};
+  if (some_link == NULL) {
+    return list;
+  }
+
+  /* Find the first element. */
+  while (((Link *)list.first)->prev != NULL) {
+    list.first = ((Link *)list.first)->prev;
+  }
+
+  /* Find the last element. */
+  while (((Link *)list.last)->next != NULL) {
+    list.last = ((Link *)list.last)->next;
+  }
+
+  return list;
+}
+
 void BLI_duplicatelist(ListBase *dst, const ListBase *src)
 {
   struct Link *dst_link, *src_link;
diff --git a/source/blender/blenlib/tests/BLI_listbase_test.cc b/source/blender/blenlib/tests/BLI_listbase_test.cc
index d66eb214902..9e4d7c7dd36 100644
--- a/source/blender/blenlib/tests/BLI_listbase_test.cc
+++ b/source/blender/blenlib/tests/BLI_listbase_test.cc
@@ -154,6 +154,31 @@ TEST(listbase, FindLinkFromStringOrPointer)
   BLI_freelistN(&lb);
 }
 
+TEST(listbase, FromLink)
+{
+  ListBase lb = {nullptr, nullptr};
+  Link *link1 = static_cast<Link *>(MEM_callocN(sizeof(Link), "link1"));
+  Link *link2 = static_cast<Link *>(MEM_callocN(sizeof(Link), "link2"));
+  Link *link3 = static_cast<Link *>(MEM_callocN(sizeof(Link), "link3"));
+
+  /* NULL safety. */
+  EXPECT_EQ(lb, BLI_listbase_from_link(nullptr));
+
+  /* One link. */
+  BLI_addtail(&lb, link1);
+  EXPECT_EQ(lb, BLI_listbase_from_link(link1));
+
+  /* Two links. */
+  BLI_addtail(&lb, link2);
+  EXPECT_EQ(lb, BLI_listbase_from_link(link2));
+
+  /* Three links, search from middle. */
+  BLI_addtail(&lb, link3);
+  EXPECT_EQ(lb, BLI_listbase_from_link(link2));
+
+  BLI_freelistN(&lb);
+}
+
 /* -------------------------------------------------------------------- */
 /* Sort utilities & test */
 
diff --git a/source/blender/blenloader/intern/versioning_300.c b/source/blender/blenloader/intern/versioning_300.c
index 7a7f12a7e58..6b22d2f97e9 100644
--- a/source/blender/blenloader/intern/versioning_300.c
+++ b/source/blender/blenloader/intern/versioning_300.c
@@ -30,6 +30,7 @@
 #include "BLI_math_vector.h"
 #include "BLI_path_util.h"
 #include "BLI_string.h"
+#include "BLI_string_utils.h"
 #include "BLI_utildefines.h"
 
 #include "DNA_anim_types.h"
@@ -790,6 +791,32 @@ void do_versions_after_linking_300(Main *bmain, ReportList *UNUSED(reports))
    */
   {
     /* Keep this block, even when empty. */
+
+    { /* Ensure driver variable names are unique within the driver. */
+      ID *id;
+      FOREACH_MAIN_ID_BEGIN (bmain, id) {
+        AnimData *adt = BKE_animdata_from_id(id);
+        if (adt == NULL) {
+          continue;
+        }
+        LISTBASE_FOREACH (FCurve *, fcu, &adt->drivers) {
+          ChannelDriver *driver = fcu->driver;
+          /* Ensure the uniqueness front to back. Given a list of identically
+           * named variables, the last one gets to keep its original name. This
+           * matches the evaluation order, and thus shouldn't change the evaluated
+           * value of the driver expression. */
+          LISTBASE_FOREACH (DriverVar *, dvar, &driver->variables) {
+            BLI_uniquename(&driver->variables,
+                           dvar,
+                           dvar->name,
+                           '_',
+                           offsetof(DriverVar, name),
+                           sizeof(dvar->name));
+          }
+        }
+      }
+      FOREACH_MAIN_ID_END;
+    }
   }
 }
 
diff --git a/source/blender/makesrna/intern/rna_fcurve.c b/source/blender/makesrna/intern/rna_fcurve.c
index a38bbd3d6d2..d3175c445a9 100644
--- a/source/blender/makesrna/intern/rna_fcurve.c
+++ b/source/blender/makesrna/intern/rna_fcurve.c
@@ -388,6 +388,7 @@ void rna_DriverVariable_name_set(PointerRNA *ptr, const char *value)
 
   BLI_strncpy_utf8(data->name, value, 64);
   driver_variable_name_validate(data);
+  driver_variable_unique_name(data);
 }
 
 /* ----------- */