Define a portable Skill bundle format

crates/buzz-persona/Cargo.toml

@@ -7,9 +7,11 @@ license = "Apache-2.0"
 repository = "https://github.com/block/sprout"
 
 [dependencies]
+hex = { workspace = true }
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 serde_yaml = "0.9"
+sha2 = { workspace = true }
 thiserror = "2"
 
 [dev-dependencies]

crates/buzz-persona/src/lib.rs

@@ -3,4 +3,6 @@ pub mod merge;
 pub mod pack;
 pub mod persona;
 pub mod resolve;
+pub mod reviewable_text;
+pub mod skill_bundle;
 pub mod validate;

crates/buzz-persona/src/reviewable_text.rs

@@ -0,0 +1,122 @@
+//! Validation for instruction text that must be reviewed exactly as executed.
+
+/// Reject control and formatting characters that can conceal instruction bytes.
+pub fn validate_reviewable_text(
+    value: &str,
+    label: &str,
+    allow_layout_controls: bool,
+) -> Result<(), String> {
+    for character in value.chars() {
+        let allowed_layout_control = allow_layout_controls && matches!(character, '\n' | '\t');
+        if (!allowed_layout_control && character.is_control())
+            || is_unicode_line_or_paragraph_separator(character)
+            || is_unicode_format(character)
+            || is_default_ignorable(character)
+        {
+            return Err(format!(
+                "{label} contains prohibited invisible or formatting character U+{:04X}",
+                character as u32
+            ));
+        }
+    }
+    Ok(())
+}
+
+/// Unicode line and paragraph separators (`Zl` and `Zp`).
+fn is_unicode_line_or_paragraph_separator(character: char) -> bool {
+    matches!(character, '\u{2028}' | '\u{2029}')
+}
+
+/// Unicode general category `Cf` ranges from DerivedGeneralCategory 17.0.0.
+fn is_unicode_format(character: char) -> bool {
+    matches!(
+        character,
+        '\u{00AD}'
+            | '\u{0600}'..='\u{0605}'
+            | '\u{061C}'
+            | '\u{06DD}'
+            | '\u{070F}'
+            | '\u{0890}'..='\u{0891}'
+            | '\u{08E2}'
+            | '\u{180E}'
+            | '\u{200B}'..='\u{200F}'
+            | '\u{202A}'..='\u{202E}'
+            | '\u{2060}'..='\u{2064}'
+            | '\u{2066}'..='\u{206F}'
+            | '\u{FEFF}'
+            | '\u{FFF9}'..='\u{FFFB}'
+            | '\u{110BD}'
+            | '\u{110CD}'
+            | '\u{13430}'..='\u{1343F}'
+            | '\u{1BCA0}'..='\u{1BCA3}'
+            | '\u{1D173}'..='\u{1D17A}'
+            | '\u{E0001}'
+            | '\u{E0020}'..='\u{E007F}'
+    )
+}
+
+/// Unicode `Default_Ignorable_Code_Point` ranges from DerivedCoreProperties.
+fn is_default_ignorable(character: char) -> bool {
+    matches!(
+        character as u32,
+        0x00AD
+            | 0x034F
+            | 0x061C
+            | 0x115F..=0x1160
+            | 0x17B4..=0x17B5
+            | 0x180B..=0x180F
+            | 0x200B..=0x200F
+            | 0x202A..=0x202E
+            | 0x2060..=0x206F
+            | 0x3164
+            | 0xFE00..=0xFE0F
+            | 0xFEFF
+            | 0xFFA0
+            | 0xFFF0..=0xFFF8
+            | 0x1BCA0..=0x1BCA3
+            | 0x1D173..=0x1D17A
+            | 0xE0000..=0xE0FFF
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn accepts_visible_text_and_requested_layout_controls() {
+        assert!(validate_reviewable_text(
+            "Review changes.\n\tCall out security risks.",
+            "Instructions",
+            true,
+        )
+        .is_ok());
+    }
+
+    #[test]
+    fn rejects_default_ignorable_and_non_layout_control_characters() {
+        for character in [
+            '\u{00AD}',
+            '\u{034F}',
+            '\u{200B}',
+            '\u{200D}',
+            '\u{202E}',
+            '\u{2060}',
+            '\u{2066}',
+            '\u{3164}',
+            '\u{FE0F}',
+            '\u{2028}',
+            '\u{2029}',
+            '\u{0600}',
+            '\u{13430}',
+            '\u{E007F}',
+            '\0',
+            '\r',
+            '\u{0007}',
+            '\u{0085}',
+        ] {
+            let value = format!("Review{character}changes");
+            assert!(validate_reviewable_text(&value, "Instructions", true).is_err());
+        }
+    }
+}