When returning a SyntaxReference, also return the SyntaxSet that contains it (#1776)

To improve startup performance, we will later load smaller `SyntaxSet`s instead
of one giant one. However, the current API assumes only one `SyntaxSet` is ever used,
and that that implicitly is the `SyntaxSet` from which returned `SyntaxReference`s
comes.

This change changes the API to reflect that `SyntaxSet` and `SyntaxReference`
are tightly coupled, and enables the use of several `SyntaxSet`.

4 files changed, 73 insertions, 43 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b15745c8..e78f8147 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,7 +26,7 @@
 
 ## `bat` as a library
 
-- Deprecate `HighlightingAssets::syntaxes()` and `HighlightingAssets::syntax_for_file_name()`. Use `HighlightingAssets::get_syntaxes()` and `HighlightingAssets::get_syntax_for_file_name()` instead. They return a `Result` which is needed for upcoming lazy-loading work to improve startup performance. See #1747 and #1755 (@Enselic)
+- Deprecate `HighlightingAssets::syntaxes()` and `HighlightingAssets::syntax_for_file_name()`. Use `HighlightingAssets::get_syntaxes()` and `HighlightingAssets::get_syntax_for_file_name()` instead. They return a `Result` which is needed for upcoming lazy-loading work to improve startup performance. They also return what `SyntaxSet` the returned `SyntaxReference` belongs to. See #1747, #1755 and #1776 (@Enselic)
 
 
 
diff --git a/src/assets.rs b/src/assets.rs
index 7c8273fb..ba60274d 100644
--- a/src/assets.rs
+++ b/src/assets.rs
@@ -25,6 +25,12 @@ pub struct HighlightingAssets {
     fallback_theme: Option<&'static str>,
 }
 
+#[derive(Debug)]
+pub struct SyntaxReferenceInSet<'a> {
+    pub syntax: &'a SyntaxReference,
+    pub syntax_set: &'a SyntaxSet,
+}
+
 const IGNORED_SUFFIXES: [&str; 10] = [
     // Editor etc backups
     "~",
@@ -217,21 +223,26 @@ impl HighlightingAssets {
         file_name: impl AsRef<Path>,
         mapping: &SyntaxMapping,
     ) -> Option<&SyntaxReference> {
-        self.get_syntax_for_file_name(file_name, mapping).expect(
-            ".syntax_for_file_name() is deprecated, use .get_syntax_for_file_name() instead",
-        )
+        self.get_syntax_for_file_name(file_name, mapping)
+            .expect(
+                ".syntax_for_file_name() is deprecated, use .get_syntax_for_file_name() instead",
+            )
+            .map(|syntax_in_set| syntax_in_set.syntax)
     }
 
     pub fn get_syntax_for_file_name(
         &self,
         file_name: impl AsRef<Path>,
         mapping: &SyntaxMapping,
-    ) -> Result<Option<&SyntaxReference>> {
+    ) -> Result<Option<SyntaxReferenceInSet>> {
         let file_name = file_name.as_ref();
         Ok(match mapping.get_syntax_for(file_name) {
             Some(MappingTarget::MapToUnknown) => None,
             Some(MappingTarget::MapTo(syntax_name)) => {
-                self.get_syntax_set()?.find_syntax_by_name(syntax_name)
+                let syntax_set = self.get_syntax_set()?;
+                syntax_set
+                    .find_syntax_by_name(syntax_name)
+                    .map(|syntax| SyntaxReferenceInSet { syntax, syntax_set })
             }
             None => self.get_extension_syntax(file_name.as_os_str())?,
         })
@@ -259,10 +270,12 @@ impl HighlightingAssets {
         language: Option<&str>,
         input: &mut OpenedInput,
         mapping: &SyntaxMapping,
-    ) -> Result<&SyntaxReference> {
+    ) -> Result<SyntaxReferenceInSet> {
         if let Some(language) = language {
-            self.get_syntax_set()?
+            let syntax_set = self.get_syntax_set()?;
+            syntax_set
                 .find_syntax_by_token(language)
+                .map(|syntax| SyntaxReferenceInSet { syntax, syntax_set })
                 .ok_or_else(|| ErrorKind::UnknownSyntax(language.to_owned()).into())
         } else {
             let line_syntax = self.get_first_line_syntax(&mut input.reader)?;
@@ -293,10 +306,13 @@ impl HighlightingAssets {
                         ErrorKind::UndetectedSyntax(path.to_string_lossy().into()).into()
                     }),
 
-                    Some(MappingTarget::MapTo(syntax_name)) => self
-                        .get_syntax_set()?
-                        .find_syntax_by_name(syntax_name)
-                        .ok_or_else(|| ErrorKind::UnknownSyntax(syntax_name.to_owned()).into()),
+                    Some(MappingTarget::MapTo(syntax_name)) => {
+                        let syntax_set = self.get_syntax_set()?;
+                        syntax_set
+                            .find_syntax_by_name(syntax_name)
+                            .map(|syntax| SyntaxReferenceInSet { syntax, syntax_set })
+                            .ok_or_else(|| ErrorKind::UnknownSyntax(syntax_name.to_owned()).into())
+                    }
 
                     None => {
                         let file_name = path.file_name().unwrap_or_default();
@@ -314,7 +330,7 @@ impl HighlightingAssets {
         }
     }
 
-    fn get_extension_syntax(&self, file_name: &OsStr) -> Result<Option<&SyntaxReference>> {
+    fn get_extension_syntax(&self, file_name: &OsStr) -> Result<Option<SyntaxReferenceInSet>> {
         let mut syntax = self.find_syntax_by_file_name(file_name)?;
         if syntax.is_none() {
             syntax = self.find_syntax_by_file_name_extension(file_name)?;
@@ -325,23 +341,27 @@ impl HighlightingAssets {
         Ok(syntax)
     }
 
-    fn find_syntax_by_file_name(&self, file_name: &OsStr) -> Result<Option<&SyntaxReference>> {
-        Ok(self
-            .get_syntax_set()?
-            .find_syntax_by_extension(file_name.to_str().unwrap_or_default()))
+    fn find_syntax_by_file_name(&self, file_name: &OsStr) -> Result<Option<SyntaxReferenceInSet>> {
+        let syntax_set = self.get_syntax_set()?;
+        Ok(syntax_set
+            .find_syntax_by_extension(file_name.to_str().unwrap_or_default())
+            .map(|syntax| SyntaxReferenceInSet { syntax, syntax_set }))
     }
 
     fn find_syntax_by_file_name_extension(
         &self,
         file_name: &OsStr,
-    ) -> Result<Option<&SyntaxReference>> {
+    ) -> Result<Option<SyntaxReferenceInSet>> {
         let file_path = Path::new(file_name);
-        Ok(self.get_syntax_set()?.find_syntax_by_extension(
-            file_path
-                .extension()
-                .and_then(|x| x.to_str())
-                .unwrap_or_default(),
-        ))
+        let syntax_set = self.get_syntax_set()?;
+        Ok(syntax_set
+            .find_syntax_by_extension(
+                file_path
+                    .extension()
+                    .and_then(|x| x.to_str())
+                    .unwrap_or_default(),
+            )
+            .map(|syntax| SyntaxReferenceInSet { syntax, syntax_set }))
     }
 
     /// If we find an ignored suffix on the file name, e.g. '~', we strip it and
@@ -349,7 +369,7 @@ impl HighlightingAssets {
     fn get_extension_syntax_with_stripped_suffix(
         &self,
         file_name: &OsStr,
-    ) -> Result<Option<&SyntaxReference>> {
+    ) -> Result<Option<SyntaxReferenceInSet>> {
         let file_path = Path::new(file_name);
         let mut syntax = None;
         if let Some(file_str) = file_path.to_str() {
@@ -363,11 +383,15 @@ impl HighlightingAssets {
         Ok(syntax)
     }
 
-    fn get_first_line_syntax(&self, reader: &mut InputReader) -> Result<Option<&SyntaxReference>> {
+    fn get_first_line_syntax(
+        &self,
+        reader: &mut InputReader,
+    ) -> Result<Option<SyntaxReferenceInSet>> {
         let syntax_set = self.get_syntax_set()?;
         Ok(String::from_utf8(reader.first_line.clone())
             .ok()
-            .and_then(|l| syntax_set.find_syntax_by_first_line(&l)))
+            .and_then(|l| syntax_set.find_syntax_by_first_line(&l))
+            .map(|syntax| SyntaxReferenceInSet { syntax, syntax_set }))
     }
 }
 
@@ -462,7 +486,7 @@ mod tests {
         ) -> String {
             self.assets
                 .get_syntax(language, input, mapping)
-                .map(|syntax| syntax.name.clone())
+                .map(|syntax_in_set| syntax_in_set.syntax.name.clone())
                 .unwrap_or_else(|_| "!no syntax!".to_owned())
         }
 
diff --git a/src/bin/bat/main.rs b/src/bin/bat/main.rs
index 7369dc03..173ac551 100644
--- a/src/bin/bat/main.rs
+++ b/src/bin/bat/main.rs
@@ -101,11 +101,11 @@ pub fn get_languages(config: &Config) -> Result<String> {
                 true
             } else {
                 let test_file = Path::new("test").with_extension(extension);
-                let syntax = assets
+                let syntax_in_set = assets
                     .get_syntax_for_file_name(test_file, &config.syntax_mapping)
                     .unwrap(); // safe since .get_syntaxes() above worked
-                match syntax {
-                    Some(syntax) => syntax.name == lang_name,
+                match syntax_in_set {
+                    Some(syntax_in_set) => syntax_in_set.syntax.name == lang_name,
                     None => false,
                 }
             }
diff --git a/src/printer.rs b/src/printer.rs
index 22d7c22d..f07d2db1 100644
--- a/src/printer.rs
+++ b/src/printer.rs
@@ -18,7 +18,7 @@ use encoding::{DecoderTrap, Encoding};
 
 use unicode_width::UnicodeWidthChar;
 
-use crate::assets::HighlightingAssets;
+use crate::assets::{HighlightingAssets, SyntaxReferenceInSet};
 use crate::config::Config;
 #[cfg(feature = "git")]
 use crate::decorations::LineChangesDecoration;
@@ -163,23 +163,29 @@ impl<'a> InteractivePrinter<'a> {
             panel_width = 0;
         }
 
-        let highlighter = if input
+        let (highlighter, syntax_set) = if input
             .reader
             .content_type
             .map_or(false, |c| c.is_binary() && !config.show_nonprintable)
         {
-            None
+            (None, assets.get_syntax_set()?)
         } else {
             // Determine the type of syntax for highlighting
-            let syntax = match assets.get_syntax(config.language, input, &config.syntax_mapping) {
-                Ok(syntax) => syntax,
-                Err(Error(ErrorKind::UndetectedSyntax(_), _)) => {
-                    assets.get_syntax_set()?.find_syntax_plain_text()
-                }
-                Err(e) => return Err(e),
-            };
+            let syntax_in_set =
+                match assets.get_syntax(config.language, input, &config.syntax_mapping) {
+                    Ok(syntax_in_set) => syntax_in_set,
+                    Err(Error(ErrorKind::UndetectedSyntax(_), _)) => {
+                        let syntax_set = assets.get_syntax_set()?;
+                        let syntax = syntax_set.find_syntax_plain_text();
+                        SyntaxReferenceInSet { syntax, syntax_set }
+                    }
+                    Err(e) => return Err(e),
+                };
 
-            Some(HighlightLines::new(syntax, theme))
+            (
+                Some(HighlightLines::new(syntax_in_set.syntax, theme)),
+                syntax_in_set.syntax_set,
+            )
         };
 
         Ok(InteractivePrinter {
@@ -192,7 +198,7 @@ impl<'a> InteractivePrinter<'a> {
             #[cfg(feature = "git")]
             line_changes,
             highlighter,
-            syntax_set: assets.get_syntax_set()?,
+            syntax_set,
             background_color_highlight,
         })
     }