.ssp digests: report missing or unreadable image

image digest: record missing or unreadable image, do not abort

safeComputeHashAndSize() open image with guard, so a document
naming an image absent from media/image/ throws
ErrnoException out of the abstraction stage.

as with _image_dimensions() (which warns and continues where issue
with image) warn to stdout and record the fact in the abstraction:

  .image: ffa.png missing:true

the abstraction would now state that the object embeds an image it
could not read, rather than the .ssp resemble one produced from a
complete pod. The sha256 summary line marks the same case
MISSING OR UNREADABLE.

(assisted by Claude-Code)

1 files changed, 18 insertions, 6 deletions

diff --git a/src/sisudoc/ocda/meta/metadoc_from_src_functions.d b/src/sisudoc/ocda/meta/metadoc_from_src_functions.d
index 791c002..6e4aec3 100644
--- a/src/sisudoc/ocda/meta/metadoc_from_src_functions.d
+++ b/src/sisudoc/ocda/meta/metadoc_from_src_functions.d
@@ -3191,13 +3191,23 @@ template docAbstractionFunctions() {
   ) {
     ST_file_name_hash_size_ safeComputeHashAndSize(N,P)(N filename, P file_path) @trusted {
       auto file_with_path = file_path ~ filename;
-      auto file_read = File(file_with_path, "r");
-      ubyte[32] file_sha256 = digest!SHA256(file_read.byChunk(4096 * 1024));
-      ulong fileSize = file_read.size;
       ST_file_name_hash_size_ _file_info;
-      _file_info.fileHash_sha256 = file_sha256;
-      _file_info.fileSize = fileSize;
       _file_info.fileName = filename;
+      /+ ↓ a referenced image that is absent or unreadable is recorded as
+         such rather than aborting the abstraction (compare the WARNING
+         issued by _image_dimensions for the same situation)
+      +/
+      try {
+        auto file_read = File(file_with_path, "r");
+        ubyte[32] file_sha256 = digest!SHA256(file_read.byChunk(4096 * 1024));
+        ulong fileSize = file_read.size;
+        _file_info.fileHash_sha256 = file_sha256;
+        _file_info.fileSize = fileSize;
+      } catch (Exception ex) {
+        _file_info.fileMissing = true;
+        writeln("WARNING, image not found or unreadable: ", filename,
+          "\n  ", file_with_path);
+      }
       return _file_info;
     }
     obj.metainfo.sha256.text = obj.text.sha256Of;
@@ -3224,7 +3234,9 @@ template docAbstractionFunctions() {
       char[] image_summary;
       if (obj.metainfo.sha256.images.length > 0) {
         foreach (i; obj.metainfo.sha256.images) {
-          image_summary ~= "\n     - " ~ i.fileHash_sha256.toHexString ~ "::" ~ i.fileSize.to!string ~ " - " ~ i.fileName;
+          image_summary ~= (i.fileMissing)
+          ? "\n     - " ~ "MISSING OR UNREADABLE" ~ " - " ~ i.fileName
+          : "\n     - " ~ i.fileHash_sha256.toHexString ~ "::" ~ i.fileSize.to!string ~ " - " ~ i.fileName;
         }
       }
       obj.metainfo.sha256.summary ~=