Changes error reporting to an Error, Warn, and Ignore model

Author: tanzaku

src/config/mod.rs

@@ -179,7 +179,8 @@ create_config! {
          or they are left with trailing whitespaces";
     ignore: IgnoreList, IgnoreList::default(), false,
         "Skip formatting the specified files and directories";
-    ignore_missing_submod: bool, false, false, "Ignore missing submodule error";
+    report_missing_submod: ReportMissingSubmod, ReportMissingSubmod::Error, false,
+        "Report missing submodule";
 
     // Not user-facing
     verbose: Verbosity, Verbosity::Normal, false, "How much to information to emit to the user";
@@ -698,7 +699,7 @@ show_parse_errors = true
 error_on_line_overflow = false
 error_on_unformatted = false
 ignore = []
-ignore_missing_submod = false
+report_missing_submod = "Error"
 emit_mode = "Files"
 make_backup = false
 "#,

src/config/options.rs

@@ -494,3 +494,14 @@ pub enum StyleEdition {
     /// [Edition 2024]().
     Edition2024,
 }
+
+/// Controls whether to report missing submodules and whether rustfmt will format.
+#[config_type]
+pub enum ReportMissingSubmod {
+    /// Missing modules will lead to module not found errors and rustfmt won't format anything.
+    Error,
+    /// Missing modules will lead to module not found warnings and rustfmt will format.
+    Warn,
+    /// Ignores missing submodule error and rustfmt will format.
+    Ignore,
+}

src/formatting.rs

@@ -135,7 +135,7 @@ fn format_project<T: FormatHandler>(
         &context.parse_session,
         directory_ownership.unwrap_or(DirectoryOwnership::UnownedViaBlock),
         !input_is_stdin && !config.skip_children(),
-        config.ignore_missing_submod(),
+        config.report_missing_submod(),
     )
     .visit_crate(&krate)?
     .into_iter()

src/modules.rs

@@ -10,7 +10,7 @@ use thin_vec::ThinVec;
 use thiserror::Error;
 
 use crate::attr::MetaVisitor;
-use crate::config::FileName;
+use crate::config::{FileName, ReportMissingSubmod};
 use crate::items::is_mod_decl;
 use crate::parse::parser::{
     Directory, DirectoryOwnership, ModError, ModulePathSuccess, Parser, ParserError,
@@ -62,7 +62,7 @@ pub(crate) struct ModResolver<'ast, 'sess> {
     directory: Directory,
     file_map: FileModMap<'ast>,
     recursive: bool,
-    ignore_missing_submod: bool,
+    report_missing_submod: ReportMissingSubmod,
 }
 
 /// Represents errors while trying to resolve modules.
@@ -106,7 +106,7 @@ impl<'ast, 'sess, 'c> ModResolver<'ast, 'sess> {
         parse_sess: &'sess ParseSess,
         directory_ownership: DirectoryOwnership,
         recursive: bool,
-        ignore_missing_submod: bool,
+        report_missing_submod: ReportMissingSubmod,
     ) -> Self {
         ModResolver {
             directory: Directory {
@@ -116,7 +116,7 @@ impl<'ast, 'sess, 'c> ModResolver<'ast, 'sess> {
             file_map: BTreeMap::new(),
             parse_sess,
             recursive,
-            ignore_missing_submod,
+            report_missing_submod,
         }
     }
 
@@ -254,10 +254,16 @@ impl<'ast, 'sess, 'c> ModResolver<'ast, 'sess> {
             self.find_external_module(item.ident, &item.attrs, sub_mod)
                 .or_else(|err| match err.kind {
                     ModuleResolutionErrorKind::NotFound { file: _ }
-                        if self.ignore_missing_submod =>
+                        if self.report_missing_submod == ReportMissingSubmod::Ignore =>
                     {
                         Ok(None)
                     }
+                    ModuleResolutionErrorKind::NotFound { file: _ }
+                        if self.report_missing_submod == ReportMissingSubmod::Warn =>
+                    {
+                        eprintln!("Warning: {}", err);
+                        Ok(None)
+                    }
                     _ => Err(err),
                 })
         } else {