xml: markup language attributes take a bcp 47 tag

Spine names a language as the directory under media/text/ is
named, which for a region is the posix form with an underscore,
pt_BR. A lang, xml:lang or dc:language value is a BCP 47 (RFC
3066) tag and wants a hyphen, pt-BR. Spine put its own code
there unchanged, so a document in a region language produced an
invalid attribute in every one of its xhtml files: 138 epubcheck
errors for a document of ten segments and a navigation file.

src.language_tag is the same language as a tag. The attributes
and the dc metadata now read it. Output paths keep src.language,
since a path is named after the directory, not after the tag.

(assisted by Claude-Code)

5 files changed, 50 insertions, 20 deletions

diff --git a/org/default_paths.org b/org/default_paths.org
index a6cf19a..15f196f 100644
--- a/org/default_paths.org
+++ b/org/default_paths.org
@@ -310,6 +310,21 @@ template PathMatters() {
           string language() {
             return lng();
           }
+          /+ ↓ the same language, as a language tag rather than as spine's
+               own code. Spine names a language the way a directory under
+               media/text/ is named, which for a region is the posix form
+               with an underscore, pt_BR. A lang, xml:lang or dc:language
+               value is a BCP 47 (RFC 3066) tag and wants a hyphen, pt-BR;
+               an underscore there is invalid and every xhtml file in the
+               document carrying it is an epubcheck error. Every other code
+               spine knows (from the document sample set) is two letters,
+               where the two forms are equal, which is why only a region
+               code shows this up.
+          +/
+          string language_tag() {
+            import std.array : replace;
+            return lng().replace("_", "-");
+          }
           string file_with_absolute_path() {
             return _env["pwd"].chainPath(path_and_fn).array;
           }
diff --git a/org/out_xmls.org b/org/out_xmls.org
index 75d61a0..90218bd 100644
--- a/org/out_xmls.org
+++ b/org/out_xmls.org
@@ -427,7 +427,7 @@ string header_metadata(M)(
     special_characters_plain(doc_matters.conf_make_meta.meta.date_available),
     special_characters_plain(doc_matters.conf_make_meta.meta.date_valid),
     special_characters_plain(doc_matters.conf_make_meta.meta.date_modified),
-    doc_matters.src.language,
+    doc_matters.src.language_tag,
     special_characters_plain(doc_matters.conf_make_meta.meta.rights_copyright),
     doc_matters.opt.action.generated_by ? special_characters_plain(doc_matters.generator_program.name_and_version) : "",
     special_characters_plain(doc_matters.generator_program.url_home),
@@ -612,7 +612,7 @@ string html_head(M)(
     ((type == "seg")
       ? "../../../css/html_seg.css"
       : "../../css/html_scroll.css"),
-    doc_matters.src.language,
+    doc_matters.src.language_tag,
     site_info_button(doc_matters),
     metadata_links,
     inline_search_form(doc_matters),
@@ -636,16 +636,16 @@ string epub3_seg_head(M)(
   xmlns="http://www.w3.org/1999/xhtml"
   xmlns:epub="http://www.idpf.org/2007/ops"
   lang="%s" xml:lang="%s">┃",
-    doc_matters.src.language,
-    doc_matters.src.language,
+    doc_matters.src.language_tag,
+    doc_matters.src.language_tag,
   );
   string html_strict = format(q"┃<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
      "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml"
   xmlns:epub="http://www.idpf.org/2007/ops"
   lang="%s" xml:lang="%s">┃",
-    doc_matters.src.language,
-    doc_matters.src.language,
+    doc_matters.src.language_tag,
+    doc_matters.src.language_tag,
   );
   string o;
   o = format(q"┃%s
@@ -685,11 +685,11 @@ string epub3_seg_head(M)(
     special_characters_plain(doc_matters.conf_make_meta.meta.date_available),
     special_characters_plain(doc_matters.conf_make_meta.meta.date_valid),
     special_characters_plain(doc_matters.conf_make_meta.meta.date_modified),
-    doc_matters.src.language,
+    doc_matters.src.language_tag,
     special_characters_plain(doc_matters.conf_make_meta.meta.rights_copyright),
     special_characters_plain(doc_matters.generator_program.name_and_version),
     special_characters_plain(doc_matters.generator_program.url_home),
-    doc_matters.src.language,
+    doc_matters.src.language_tag,
   );
   return o;
 }
@@ -2938,7 +2938,7 @@ string epub3_oebps_content(D,P)(D doc, P parts) {
     <item id="css" href="%s" media-type="text/css"/>
     <item id="nav" href="toc_nav.xhtml" media-type="application/xhtml+xml" properties="nav" />
 ┃",
-    doc.matters.src.language,
+    doc.matters.src.language_tag,
     _uuid,
     xhtml_format.special_characters_plain(doc.matters.conf_make_meta.meta.title_main),
     (doc.matters.conf_make_meta.meta.title_sub.empty) ? "" : format(
@@ -2949,7 +2949,7 @@ string epub3_oebps_content(D,P)(D doc, P parts) {
       ? "" : xhtml_format.special_characters_plain(doc.matters.conf_make_meta.meta.creator_author),
     (doc.matters.conf_make_meta.meta.creator_author_surname_fn.empty)
       ? "" : xhtml_format.special_characters_plain(doc.matters.conf_make_meta.meta.creator_author_surname_fn),
-    doc.matters.src.language,                                   // language, fix (needed in dochead metadata)
+    doc.matters.src.language_tag,                                   // language, fix (needed in dochead metadata)
     (doc.matters.conf_make_meta.meta.date_published.empty)
       ? "" : xhtml_format.special_characters_plain_date(doc.matters.conf_make_meta.meta.date_published),
     (doc.matters.conf_make_meta.meta.rights_copyright.empty)
diff --git a/src/sisudoc/ocda/io_in/paths_source.d b/src/sisudoc/ocda/io_in/paths_source.d
index 9cacdf0..f32b89e 100644
--- a/src/sisudoc/ocda/io_in/paths_source.d
+++ b/src/sisudoc/ocda/io_in/paths_source.d
@@ -298,6 +298,21 @@ template PathMatters() {
           string language() {
             return lng();
           }
+          /+ ↓ the same language, as a language tag rather than as spine's
+               own code. Spine names a language the way a directory under
+               media/text/ is named, which for a region is the posix form
+               with an underscore, pt_BR. A lang, xml:lang or dc:language
+               value is a BCP 47 (RFC 3066) tag and wants a hyphen, pt-BR;
+               an underscore there is invalid and every xhtml file in the
+               document carrying it is an epubcheck error. Every other code
+               spine knows (from the document sample set) is two letters,
+               where the two forms are equal, which is why only a region
+               code shows this up.
+          +/
+          string language_tag() {
+            import std.array : replace;
+            return lng().replace("_", "-");
+          }
           string file_with_absolute_path() {
             return _env["pwd"].chainPath(path_and_fn).array;
           }
diff --git a/src/sisudoc/outputs/io_out/epub3.d b/src/sisudoc/outputs/io_out/epub3.d
index 8a3baaf..c785895 100644
--- a/src/sisudoc/outputs/io_out/epub3.d
+++ b/src/sisudoc/outputs/io_out/epub3.d
@@ -298,7 +298,7 @@ template outputEPub3() {
       <item id="css" href="%s" media-type="text/css"/>
       <item id="nav" href="toc_nav.xhtml" media-type="application/xhtml+xml" properties="nav" />
   ┃",
-      doc.matters.src.language,
+      doc.matters.src.language_tag,
       _uuid,
       xhtml_format.special_characters_plain(doc.matters.conf_make_meta.meta.title_main),
       (doc.matters.conf_make_meta.meta.title_sub.empty) ? "" : format(
@@ -309,7 +309,7 @@ template outputEPub3() {
         ? "" : xhtml_format.special_characters_plain(doc.matters.conf_make_meta.meta.creator_author),
       (doc.matters.conf_make_meta.meta.creator_author_surname_fn.empty)
         ? "" : xhtml_format.special_characters_plain(doc.matters.conf_make_meta.meta.creator_author_surname_fn),
-      doc.matters.src.language,                                   // language, fix (needed in dochead metadata)
+      doc.matters.src.language_tag,                                   // language, fix (needed in dochead metadata)
       (doc.matters.conf_make_meta.meta.date_published.empty)
         ? "" : xhtml_format.special_characters_plain_date(doc.matters.conf_make_meta.meta.date_published),
       (doc.matters.conf_make_meta.meta.rights_copyright.empty)
diff --git a/src/sisudoc/outputs/io_out/xmls.d b/src/sisudoc/outputs/io_out/xmls.d
index 4ce5434..c97a7e3 100644
--- a/src/sisudoc/outputs/io_out/xmls.d
+++ b/src/sisudoc/outputs/io_out/xmls.d
@@ -308,7 +308,7 @@ template outputXHTMLs() {
         special_characters_plain(doc_matters.conf_make_meta.meta.date_available),
         special_characters_plain(doc_matters.conf_make_meta.meta.date_valid),
         special_characters_plain(doc_matters.conf_make_meta.meta.date_modified),
-        doc_matters.src.language,
+        doc_matters.src.language_tag,
         special_characters_plain(doc_matters.conf_make_meta.meta.rights_copyright),
         doc_matters.opt.action.generated_by ? special_characters_plain(doc_matters.generator_program.name_and_version) : "",
         special_characters_plain(doc_matters.generator_program.url_home),
@@ -473,7 +473,7 @@ template outputXHTMLs() {
         ((type == "seg")
           ? "../../../css/html_seg.css"
           : "../../css/html_scroll.css"),
-        doc_matters.src.language,
+        doc_matters.src.language_tag,
         site_info_button(doc_matters),
         metadata_links,
         inline_search_form(doc_matters),
@@ -491,16 +491,16 @@ template outputXHTMLs() {
       xmlns="http://www.w3.org/1999/xhtml"
       xmlns:epub="http://www.idpf.org/2007/ops"
       lang="%s" xml:lang="%s">┃",
-        doc_matters.src.language,
-        doc_matters.src.language,
+        doc_matters.src.language_tag,
+        doc_matters.src.language_tag,
       );
       string html_strict = format(q"┃<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
          "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
     <html xmlns="http://www.w3.org/1999/xhtml"
       xmlns:epub="http://www.idpf.org/2007/ops"
       lang="%s" xml:lang="%s">┃",
-        doc_matters.src.language,
-        doc_matters.src.language,
+        doc_matters.src.language_tag,
+        doc_matters.src.language_tag,
       );
       string o;
       o = format(q"┃%s
@@ -540,11 +540,11 @@ template outputXHTMLs() {
         special_characters_plain(doc_matters.conf_make_meta.meta.date_available),
         special_characters_plain(doc_matters.conf_make_meta.meta.date_valid),
         special_characters_plain(doc_matters.conf_make_meta.meta.date_modified),
-        doc_matters.src.language,
+        doc_matters.src.language_tag,
         special_characters_plain(doc_matters.conf_make_meta.meta.rights_copyright),
         special_characters_plain(doc_matters.generator_program.name_and_version),
         special_characters_plain(doc_matters.generator_program.url_home),
-        doc_matters.src.language,
+        doc_matters.src.language_tag,
       );
       return o;
     }