Expand normalization checks on import/export

The old Python code was only checking for NFC encoding, but we should
check for other issues like special filenames on windows (eg con.mp3)

- On export, the user is told to use Check Media if their media has
invalid filenames.
- On import, legacy packages will be transparently normalized. Since we're
doing the checks on export as well, any invalid names in a v3 package
are an error.

ftl/core/errors.ftl

@@ -9,6 +9,7 @@ errors-100-tags-max =
     is no need to select child tags if you have selected a parent tag.
 errors-multiple-notetypes-selected = Please select notes from only one notetype.
 errors-please-check-database = Please use the Check Database action, then try again.
+errors-please-check-media = Please use the Check Media action, then try again.
 errors-collection-too-new = This collection requires a newer version of Anki to open.
 
 ## Card Rendering

rslib/src/backend/error.rs

@@ -36,6 +36,7 @@ impl AnkiError {
             AnkiError::CustomStudyError(_) => Kind::CustomStudyError,
             AnkiError::ImportError(_) => Kind::ImportError,
             AnkiError::FileIoError(_) => Kind::IoError,
+            AnkiError::MediaCheckRequired => Kind::InvalidInput,
         };
 
         pb::BackendError {

rslib/src/error/mod.rs

@@ -42,6 +42,7 @@ pub enum AnkiError {
     UndoEmpty,
     MultipleNotetypesSelected,
     DatabaseCheckRequired,
+    MediaCheckRequired,
     CustomStudyError(CustomStudyError),
     ImportError(ImportError),
 }
@@ -97,6 +98,7 @@ impl AnkiError {
             AnkiError::InvalidRegex(err) => format!("<pre>{}</pre>", err),
             AnkiError::MultipleNotetypesSelected => tr.errors_multiple_notetypes_selected().into(),
             AnkiError::DatabaseCheckRequired => tr.errors_please_check_database().into(),
+            AnkiError::MediaCheckRequired => tr.errors_please_check_media().into(),
             AnkiError::CustomStudyError(err) => err.localized_description(tr),
             AnkiError::ImportError(err) => err.localized_description(tr),
             AnkiError::IoError(_)

rslib/src/import_export/package/colpkg/export.rs

@@ -18,7 +18,9 @@ use zstd::{
 
 use super::super::{MediaEntries, MediaEntry, Meta, Version};
 use crate::{
-    collection::CollectionBuilder, media::files::sha1_of_data, prelude::*, text::normalize_to_nfc,
+    collection::CollectionBuilder,
+    media::files::{filename_if_normalized, sha1_of_data},
+    prelude::*,
 };
 
 /// Enable multithreaded compression if over this size. For smaller files,
@@ -279,16 +281,18 @@ fn make_media_entry(data: &[u8], name: String) -> MediaEntry {
 }
 
 fn normalized_unicode_file_name(entry: &DirEntry) -> Result<String> {
-    entry
-        .file_name()
-        .to_str()
-        .map(|name| normalize_to_nfc(name).into())
-        .ok_or_else(|| {
-            AnkiError::IoError(format!(
-                "non-unicode file name: {}",
-                entry.file_name().to_string_lossy()
-            ))
-        })
+    let filename = entry.file_name();
+    let filename = filename.to_str().ok_or_else(|| {
+        AnkiError::IoError(format!(
+            "non-unicode file name: {}",
+            entry.file_name().to_string_lossy()
+        ))
+    })?;
+    if let Some(filename) = filename_if_normalized(filename) {
+        Ok(filename.into_owned())
+    } else {
+        Err(AnkiError::MediaCheckRequired)
+    }
 }
 
 /// Writes media files while compressing according to the targeted version.

rslib/src/import_export/package/colpkg/import.rs

@@ -2,6 +2,7 @@
 // License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
 
 use std::{
+    borrow::Cow,
     collections::HashMap,
     fs::{self, File},
     io::{self, Read, Write},
@@ -21,8 +22,8 @@ use crate::{
         package::{MediaEntries, MediaEntry, Meta},
         ImportProgress,
     },
+    media::files::normalize_filename,
     prelude::*,
-    text::normalize_to_nfc,
 };
 
 impl Meta {
@@ -119,8 +120,8 @@ fn restore_media(
 
         if let Ok(mut zip_file) = archive.by_name(&archive_file_name.to_string()) {
             check_filename_safe(&entry.name)?;
-            let nfc_name = normalize_to_nfc(&entry.name);
-            let file_path = media_folder.join(nfc_name.as_ref());
+            let normalized = maybe_normalizing(&entry.name, meta.strict_media_checks())?;
+            let file_path = media_folder.join(normalized.as_ref());
             let size_in_colpkg = if meta.media_list_is_hashmap() {
                 zip_file.size()
             } else {
@@ -151,6 +152,18 @@ fn restore_media(
     Ok(())
 }
 
+/// - If strict is true, return an error if not normalized.
+/// - If false, return the normalized version.
+fn maybe_normalizing(name: &str, strict: bool) -> Result<Cow<str>> {
+    let normalized = normalize_filename(name);
+    if strict && matches!(normalized, Cow::Owned(_)) {
+        // exporting code should have checked this
+        Err(AnkiError::ImportError(ImportError::Corrupt))
+    } else {
+        Ok(normalized)
+    }
+}
+
 /// Return an error if name contains any path separators.
 fn check_filename_safe(name: &str) -> Result<()> {
     let mut components = Path::new(name).components();
@@ -238,4 +251,10 @@ mod test {
             assert!(check_filename_safe("\\foo").is_err());
         }
     }
+
+    #[test]
+    fn normalization() {
+        assert_eq!(&maybe_normalizing("con", false).unwrap(), "con_");
+        assert!(&maybe_normalizing("con", true).is_err());
+    }
 }

rslib/src/import_export/package/colpkg/tests.rs

@@ -68,3 +68,24 @@ fn roundtrip() -> Result<()> {
 
     Ok(())
 }
+
+/// Files with an invalid encoding should prevent export, except
+/// on Apple platforms where the encoding is transparently changed.
+#[test]
+#[cfg(not(target_vendor = "apple"))]
+fn normalization_check_on_export() -> Result<()> {
+    let _dir = tempdir()?;
+    let dir = _dir.path();
+
+    let col = collection_with_media(dir, "normalize")?;
+    let colpkg_name = dir.join("normalize.colpkg");
+    // manually write a file in the wrong encoding.
+    std::fs::write(col.media_folder.join("ぱぱ.jpg"), "nfd encoding")?;
+    assert_eq!(
+        col.export_colpkg(&colpkg_name, true, false, |_| ())
+            .unwrap_err(),
+        AnkiError::MediaCheckRequired
+    );
+
+    Ok(())
+}

rslib/src/import_export/package/meta.rs

@@ -39,6 +39,10 @@ impl Meta {
         self.is_legacy()
     }
 
+    pub(super) fn strict_media_checks(&self) -> bool {
+        !self.is_legacy()
+    }
+
     fn is_legacy(&self) -> bool {
         matches!(self.version(), Version::Legacy1 | Version::Legacy2)
     }

rslib/src/media/files.rs

@@ -133,7 +133,7 @@ pub(crate) fn normalize_nfc_filename(mut fname: Cow<str>) -> Cow<str> {
 /// but can be accessed as NFC. On these devices, if the filename
 /// is otherwise valid, the filename is returned as NFC.
 #[allow(clippy::collapsible_else_if)]
-pub(super) fn filename_if_normalized(fname: &str) -> Option<Cow<str>> {
+pub(crate) fn filename_if_normalized(fname: &str) -> Option<Cow<str>> {
     if cfg!(target_vendor = "apple") {
         if !is_nfc(fname) {
             let as_nfc = fname.chars().nfc().collect::<String>();