.ai import: a file whose PDF part can't be read opens from its editing data

Squashed from #5051 onto main.

crates/testkit/src/ai.rs

@@ -190,7 +190,19 @@ pub fn ai(private: &[u8], page: &str) -> Vec<u8> {
 
 /// [`ai`] with more entries in the page dictionary (`/ArtBox [0 0 200 100]`).
 pub fn ai_with(private: &[u8], page: &str, entries: &str) -> Vec<u8> {
-    with_private(private, page, "AIPrivateData", entries)
+    with_private(private, page, "AIPrivateData", entries, "")
+}
+
+/// [`ai`] with more entries in the dictionary of the page's content stream
+/// (`/DecodeParms << /Predictor 12 /Columns 0 >>`).
+pub fn ai_with_content(private: &[u8], page: &str, content: &str) -> Vec<u8> {
+    with_private(private, page, "AIPrivateData", "", content)
+}
+
+/// [`ai`] with more `entries` in the page dictionary, as [`ai_with`], and more in its content
+/// stream's dictionary, as [`ai_with_content`].
+pub fn ai_with_entries_and_content(private: &[u8], page: &str, entries: &str, content: &str) -> Vec<u8> {
+    with_private(private, page, "AIPrivateData", entries, content)
 }
 
 /// A PDF saved with Illustrator's editing data: [`ai`]'s file with the two streams under
@@ -198,15 +210,20 @@ pub fn ai_with(private: &[u8], page: &str, entries: &str) -> Vec<u8> {
 /// #868, and nothing else of that file is used; ExifTool's PDF tag table lists them too
 /// (<https://exiftool.org/TagNames/PDF.html>).
 pub fn pdf(private: &[u8], page: &str) -> Vec<u8> {
-    with_private(private, page, "AIPDFPrivateData", "")
+    with_private(private, page, "AIPDFPrivateData", "", "")
 }
 
-/// The file of [`ai`] and [`pdf`], with `private` in the streams `{key}1` and `{key}2` and
-/// `entries` more in the page dictionary.
-fn with_private(private: &[u8], page: &str, key: &str, entries: &str) -> Vec<u8> {
+/// [`pdf`] with more entries in the dictionary of the page's content stream, as [`ai_with_content`].
+pub fn pdf_with_content(private: &[u8], page: &str, content: &str) -> Vec<u8> {
+    with_private(private, page, "AIPDFPrivateData", "", content)
+}
+
+/// The file of [`ai`] and [`pdf`], with `private` in the streams `{key}1` and `{key}2`, `entries`
+/// more in the page dictionary and `content` more in its content stream's dictionary.
+fn with_private(private: &[u8], page: &str, key: &str, entries: &str, content: &str) -> Vec<u8> {
     let (first, second) = private.split_at(private.len() / 2);
-    let stream = |part: &[u8]| {
-        let mut s = format!("<< /Length {} >>\nstream\n", part.len()).into_bytes();
+    let stream = |part: &[u8], more: &str| {
+        let mut s = format!("<< /Length {} {more}>>\nstream\n", part.len()).into_bytes();
         s.extend_from_slice(part);
         s.extend_from_slice(b"\nendstream");
         s
@@ -220,9 +237,9 @@ fn with_private(private: &[u8], page: &str, key: &str, entries: &str) -> Vec<u8>
              /PieceInfo << /{PIECE} << /Private << /{key}1 5 0 R /{key}2 6 0 R /NumBlock 2 >> >> >> >>"
         )
         .into_bytes(),
-        stream(page.as_bytes()),
-        stream(first),
-        stream(second),
+        stream(page.as_bytes(), content),
+        stream(first, ""),
+        stream(second, ""),
     ];
     let mut out = b"%PDF-1.5\n".to_vec();
     let mut offsets = vec![];