Python API: path mapping options for library writing function

When "Relative Remap" option was added, the intention was only to remap
paths that were already relative. However it remapped all paths.

This was reported as T62612 and fixed recently,
however some Python script authors depended on the old behavior.

For users, it's reasonable to use the existing operators to make paths
absolute/relative. For scripts however it's useful to be able to write
out individual data-blocks with the ability to make all paths relative.

Now `bpy.data.libraries.write()` takes a path_remap argument which can
be `NONE/RELATIVE/RELATIVE_ALL/ABSOLUTE` allowing the script author to
choose how paths are handled when writing out data-blocks.

Addresses T77768.

2 files changed, 80 insertions, 20 deletions

diff --git a/source/blender/blenloader/BLO_writefile.h b/source/blender/blenloader/BLO_writefile.h
index d83abf7f9ed..18783474392 100644
--- a/source/blender/blenloader/BLO_writefile.h
+++ b/source/blender/blenloader/BLO_writefile.h
@@ -30,11 +30,32 @@ struct Main;
 struct MemFile;
 struct ReportList;
 
+/**
+ * Adjust paths when saving (kept unless #G_FILE_SAVE_COPY is set).
+ */
+typedef enum eBLO_WritePathRemap {
+  /** No path manipulation. */
+  BLO_WRITE_PATH_REMAP_NONE = 1,
+  /** Remap existing relative paths (default). */
+  BLO_WRITE_PATH_REMAP_RELATIVE = 2,
+  /** Remap paths making all paths relative to the new location. */
+  BLO_WRITE_PATH_REMAP_RELATIVE_ALL = 3,
+  /** Make all paths absolute. */
+  BLO_WRITE_PATH_REMAP_ABSOLUTE = 4,
+} eBLO_WritePathRemap;
+
+extern bool BLO_write_file_ex(struct Main *mainvar,
+                              const char *filepath,
+                              const int write_flags,
+                              struct ReportList *reports,
+                              /* Extra arguments. */
+                              eBLO_WritePathRemap remap_mode,
+                              const struct BlendThumbnail *thumb);
 extern bool BLO_write_file(struct Main *mainvar,
                            const char *filepath,
-                           int write_flags,
-                           struct ReportList *reports,
-                           const struct BlendThumbnail *thumb);
+                           const int write_flags,
+                           struct ReportList *reports);
+
 extern bool BLO_write_file_mem(struct Main *mainvar,
                                struct MemFile *compare,
                                struct MemFile *current,
diff --git a/source/blender/blenloader/intern/writefile.c b/source/blender/blenloader/intern/writefile.c
index a40cc4c3ad2..1cda22de941 100644
--- a/source/blender/blenloader/intern/writefile.c
+++ b/source/blender/blenloader/intern/writefile.c
@@ -4400,11 +4400,13 @@ static bool do_history(const char *name, ReportList *reports)
 /**
  * \return Success.
  */
-bool BLO_write_file(Main *mainvar,
-                    const char *filepath,
-                    int write_flags,
-                    ReportList *reports,
-                    const BlendThumbnail *thumb)
+bool BLO_write_file_ex(Main *mainvar,
+                       const char *filepath,
+                       const int write_flags,
+                       ReportList *reports,
+                       /* Extra arguments. */
+                       eBLO_WritePathRemap remap_mode,
+                       const BlendThumbnail *thumb)
 {
   char tempname[FILE_MAX + 1];
   eWriteWrapType ww_type;
@@ -4439,7 +4441,15 @@ bool BLO_write_file(Main *mainvar,
   }
 
   /* Remapping of relative paths to new file location. */
-  if (write_flags & G_FILE_RELATIVE_REMAP) {
+  if (remap_mode != BLO_WRITE_PATH_REMAP_NONE) {
+
+    if (remap_mode == BLO_WRITE_PATH_REMAP_RELATIVE) {
+      /* Make all relative as none of the existing paths can be relative in an unsaved document. */
+      if (G.relbase_valid == false) {
+        remap_mode = BLO_WRITE_PATH_REMAP_RELATIVE_ALL;
+      }
+    }
+
     char dir_src[FILE_MAX];
     char dir_dst[FILE_MAX];
     BLI_split_dir_part(mainvar->name, dir_src, sizeof(dir_src));
@@ -4449,23 +4459,43 @@ bool BLO_write_file(Main *mainvar,
     BLI_path_normalize(mainvar->name, dir_dst);
     BLI_path_normalize(mainvar->name, dir_src);
 
-    if (G.relbase_valid && (BLI_path_cmp(dir_dst, dir_src) == 0)) {
-      /* Saved to same path. Nothing to do. */
-      write_flags &= ~G_FILE_RELATIVE_REMAP;
+    /* Only for relative, not relative-all, as this means making existing paths relative. */
+    if (remap_mode == BLO_WRITE_PATH_REMAP_RELATIVE) {
+      if (G.relbase_valid && (BLI_path_cmp(dir_dst, dir_src) == 0)) {
+        /* Saved to same path. Nothing to do. */
+        remap_mode = BLO_WRITE_PATH_REMAP_NONE;
+      }
     }
-    else {
+    else if (remap_mode == BLO_WRITE_PATH_REMAP_ABSOLUTE) {
+      if (G.relbase_valid == false) {
+        /* Unsaved, all paths are absolute.Even if the user manages to set a relative path,
+         * there is no base-path that can be used to make it absolute. */
+        remap_mode = BLO_WRITE_PATH_REMAP_NONE;
+      }
+    }
+
+    if (remap_mode != BLO_WRITE_PATH_REMAP_NONE) {
       /* Check if we need to backup and restore paths. */
       if (UNLIKELY(G_FILE_SAVE_COPY & write_flags)) {
         path_list_backup = BKE_bpath_list_backup(mainvar, path_list_flag);
       }
 
-      if (G.relbase_valid) {
-        /* Saved, make relative paths relative to new location (if possible). */
-        BKE_bpath_relative_rebase(mainvar, dir_src, dir_dst, NULL);
-      }
-      else {
-        /* Unsaved, make all relative. */
-        BKE_bpath_relative_convert(mainvar, dir_dst, NULL);
+      switch (remap_mode) {
+        case BLO_WRITE_PATH_REMAP_RELATIVE:
+          /* Saved, make relative paths relative to new location (if possible). */
+          BKE_bpath_relative_rebase(mainvar, dir_src, dir_dst, NULL);
+          break;
+        case BLO_WRITE_PATH_REMAP_RELATIVE_ALL:
+          /* Make all relative (when requested or unsaved). */
+          BKE_bpath_relative_convert(mainvar, dir_dst, NULL);
+          break;
+        case BLO_WRITE_PATH_REMAP_ABSOLUTE:
+          /* Make all absolute (when requested or unsaved). */
+          BKE_bpath_absolute_convert(mainvar, dir_src, NULL);
+          break;
+        case BLO_WRITE_PATH_REMAP_NONE:
+          BLI_assert(0); /* Unreachable. */
+          break;
       }
     }
   }
@@ -4510,6 +4540,15 @@ bool BLO_write_file(Main *mainvar,
   return 1;
 }
 
+bool BLO_write_file(Main *mainvar,
+                    const char *filepath,
+                    const int write_flags,
+                    ReportList *reports)
+{
+  return BLO_write_file_ex(
+      mainvar, filepath, write_flags, reports, BLO_WRITE_PATH_REMAP_NONE, NULL);
+}
+
 /**
  * \return Success.
  */