[fea-rs] Move max_n_errors into Opt struct

This is in anticipation of adding additional Opts (specifically for only
compiling certain tables) and I'd like `Opts` to be the source of truth
for user configuration.

fea-rs/src/compile/compiler.rs

@@ -34,6 +34,8 @@ pub struct Compiler<'a, F: FeatureProvider, V: VariationInfo> {
     // variable fonts only
     var_info: Option<&'a V>,
     feature_writer: Option<&'a F>,
+    // this is not in `Opts` because it is specific to the compiler struct;
+    // if you're compiling manually you are responsible for handling warnings.
     print_warnings: bool,
     max_n_errors: usize,
     opts: Opts,
@@ -95,16 +97,6 @@ impl<'a, F: FeatureProvider, V: VariationInfo> Compiler<'a, F, V> {
         self
     }
 
-    /// Specify a maximum number of messages to print when errors occur.
-    ///
-    /// Default is some arbitrary 'reasonable' number (currently 100.) To
-    /// suppress errors, pass `0`. To print all errors, pass a number as large
-    /// as the number of errors you intend to write.
-    pub fn max_error_messages(mut self, max_n_errors: usize) -> Self {
-        self.max_n_errors = max_n_errors;
-        self
-    }
-
     /// Specify an explicit project root.
     ///
     /// This is useful in cases where import resolution is based on an explicit

fea-rs/src/compile/opts.rs

@@ -5,10 +5,13 @@
 // a very important part of our API, and a more natural place for us to specify
 // options is in the 'Compiler' struct itself.
 
+const DEFAULT_N_MESSAGES_TO_PRINT: usize = 100;
+
 /// Options for configuring compilation behaviour.
-#[derive(Clone, Debug, Default)]
+#[derive(Clone, Debug)]
 pub struct Opts {
     pub(crate) make_post_table: bool,
+    pub(crate) max_n_errors: usize,
 }
 
 impl Opts {
@@ -22,4 +25,24 @@ impl Opts {
         self.make_post_table = flag;
         self
     }
+
+    /// Specify the number of errors to print when printing a [`DiagnosticSet`].
+    ///
+    /// Default is some arbitrary 'reasonable' number (currently 100.) To
+    /// suppress errors, pass `0`. For 'all errors', pass `usize::MAX`.
+    ///
+    /// [`DiagnosticSet`]: crate::DiagnosticSet
+    pub fn max_error_messages(mut self, max_n_errors: usize) -> Self {
+        self.max_n_errors = max_n_errors;
+        self
+    }
+}
+
+impl Default for Opts {
+    fn default() -> Self {
+        Self {
+            make_post_table: false,
+            max_n_errors: DEFAULT_N_MESSAGES_TO_PRINT,
+        }
+    }
 }

fea-rs/src/lib.rs

@@ -16,7 +16,7 @@ pub mod util;
 mod tests;
 
 pub use common::{GlyphIdent, GlyphMap, GlyphName, GlyphSet};
-pub use compile::Compiler;
+pub use compile::{Compiler, Opts};
 pub use diagnostic::{Diagnostic, DiagnosticSet, Level};
 pub use parse::{ParseTree, TokenSet};
 pub use token_tree::{typed, Kind, Node, NodeOrToken, Token};