make module name parsing more strict

# User-Facing Changes

- Module names must now be valid identifiers, with an exception for
  hyphens:

```nushell
module foo/bar {} # × expected valid module name
module foo-bar {} # ✅
```
- Variable access in modules named with hyphens no longer causes
  "expected valid variable name" errors:

```nushell
module foo-bar { export const baz = 1 }
use foo-bar
$foo-bar.baz
```

crates/nu-command/src/system/nu_check.rs

@@ -191,7 +191,7 @@ fn parse_module(
     let new_span = working_set.get_span_for_file(file_id);
 
     let starting_error_count = working_set.parse_errors.len();
-    parse_module_block(working_set, new_span, filename.as_bytes());
+    parse_module_block(working_set, new_span, &filename.into_spanned(call_head));
 
     check_parse(
         starting_error_count,

crates/nu-parser/src/parse_keywords.rs

@@ -1,7 +1,7 @@
 use crate::{
     exportable::Exportable,
     parse_block,
-    parser::{parse_redirection, redirecting_builtin_error},
+    parser::{is_module_name, parse_redirection, redirecting_builtin_error},
     type_check::{check_block_input_output, type_compatible},
 };
 use itertools::Itertools;
@@ -15,8 +15,8 @@ use nu_protocol::{
     engine::{StateWorkingSet, DEFAULT_OVERLAY_NAME},
     eval_const::eval_constant,
     parser_path::ParserPath,
-    Alias, BlockId, DeclId, Module, ModuleId, ParseError, PositionalArg, ResolvedImportPattern,
-    Span, Spanned, SyntaxShape, Type, Value, VarId,
+    Alias, BlockId, DeclId, IntoSpanned, Module, ModuleId, ParseError, PositionalArg,
+    ResolvedImportPattern, Span, Spanned, SyntaxShape, Type, Value, VarId,
 };
 use std::{
     collections::{HashMap, HashSet},
@@ -1715,7 +1715,7 @@ fn collect_first_comments(tokens: &[Token]) -> Vec<Span> {
 pub fn parse_module_block(
     working_set: &mut StateWorkingSet,
     span: Span,
-    module_name: &[u8],
+    module_name: &Spanned<String>,
 ) -> (Block, Module, Vec<Span>) {
     working_set.enter_scope();
 
@@ -1739,6 +1739,11 @@ pub fn parse_module_block(
         }
     }
 
+    if !is_module_name(module_name.item.as_bytes()) {
+        working_set.error(ParseError::Expected("valid module name", module_name.span));
+    }
+    let module_name = module_name.item.as_bytes();
+
     let mut module = Module::from_span(module_name.to_vec(), span);
 
     let mut block = Block::new_with_capacity(output.block.len());
@@ -1948,13 +1953,13 @@ fn parse_module_file(
     working_set: &mut StateWorkingSet,
     path: ParserPath,
     path_span: Span,
-    name_override: Option<String>,
+    name_override: Option<Spanned<String>>,
 ) -> Option<ModuleId> {
     // Infer the module name from the stem of the file, unless overridden.
     let module_name = if let Some(name) = name_override {
         name
     } else if let Some(stem) = path.file_stem() {
-        stem.to_string_lossy().to_string()
+        stem.to_string_lossy().to_string().into_spanned(path_span)
     } else {
         working_set.error(ParseError::ModuleNotFound(
             path_span,
@@ -1992,14 +1997,14 @@ fn parse_module_file(
 
     // Parse the module
     let (block, mut module, module_comments) =
-        parse_module_block(working_set, new_span, module_name.as_bytes());
+        parse_module_block(working_set, new_span, &module_name);
 
     // Remove the file from the stack of files being processed.
     working_set.files.pop();
 
     let _ = working_set.add_block(Arc::new(block));
     module.file = Some((path, file_id));
-    let module_id = working_set.add_module(&module_name, module, module_comments);
+    let module_id = working_set.add_module(&module_name.item, module, module_comments);
 
     Some(module_id)
 }
@@ -2008,7 +2013,7 @@ pub fn parse_module_file_or_dir(
     working_set: &mut StateWorkingSet,
     path: &[u8],
     path_span: Span,
-    name_override: Option<String>,
+    name_override: Option<Spanned<String>>,
 ) -> Option<ModuleId> {
     let (module_path_str, err) = unescape_unquote_string(path, path_span);
     if let Some(err) = err {
@@ -2037,7 +2042,7 @@ pub fn parse_module_file_or_dir(
         };
 
         let module_name = if let Some(stem) = module_path.file_stem() {
-            stem.to_string_lossy().to_string()
+            stem.to_string_lossy().to_string().into_spanned(path_span)
         } else {
             working_set.error(ParseError::ModuleNotFound(
                 path_span,
@@ -2250,8 +2255,11 @@ pub fn parse_module(
 
     let block_span = Span::new(start, end);
 
-    let (block, module, inner_comments) =
-        parse_module_block(working_set, block_span, module_name.as_bytes());
+    let (block, module, inner_comments) = parse_module_block(
+        working_set,
+        block_span,
+        &module_name.clone().into_spanned(module_name_or_path_span),
+    );
 
     let block_id = working_set.add_block(Arc::new(block));
 
@@ -2893,7 +2901,7 @@ pub fn parse_overlay_use(working_set: &mut StateWorkingSet, call: Box<Call>) ->
                 working_set,
                 overlay_name.as_bytes(),
                 overlay_name_span,
-                new_name.as_ref().map(|spanned| spanned.item.clone()),
+                new_name.clone(),
             ) {
                 // try file or directory
                 let new_module = working_set.get_module(module_id).clone();

crates/nu-parser/src/parser.rs

@@ -126,6 +126,12 @@ pub fn is_variable(bytes: &[u8]) -> bool {
     }
 }
 
+pub fn is_module_name(bytes: &[u8]) -> bool {
+    bytes
+        .iter()
+        .all(|x| is_identifier_byte(*x) && *x != b'\\' || *x == b'-')
+}
+
 pub fn trim_quotes(bytes: &[u8]) -> &[u8] {
     if (bytes.starts_with(b"\"") && bytes.ends_with(b"\"") && bytes.len() > 1)
         || (bytes.starts_with(b"\'") && bytes.ends_with(b"\'") && bytes.len() > 1)
@@ -5559,7 +5565,7 @@ pub fn parse_expression(working_set: &mut StateWorkingSet, spans: &[Span]) -> Ex
 pub fn parse_variable(working_set: &mut StateWorkingSet, span: Span) -> Option<VarId> {
     let bytes = working_set.get_span_contents(span);
 
-    if is_variable(bytes) {
+    if is_variable(bytes) || is_module_name(bytes) {
         working_set.find_variable(bytes)
     } else {
         working_set.error(ParseError::Expected("valid variable name", span));

tests/repl/test_modules.rs

@@ -145,6 +145,14 @@ fn export_module_which_defined_const() -> TestResult {
     )
 }
 
+#[test]
+fn export_module_with_hyphen_in_name() -> TestResult {
+    run_test(
+        r#"module spam-mod { export const b = 3; }; use spam-mod; $spam-mod.b"#,
+        "3",
+    )
+}
+
 #[test]
 fn cannot_export_private_const() -> TestResult {
     fail_test(

tests/repl/test_parser.rs

@@ -186,6 +186,13 @@ fn bad_var_name3() -> TestResult {
     fail_test(r#"=foo=4 true"#, "Command `=foo=4` not found")
 }
 
+#[test]
+fn bad_module_name() -> TestResult {
+    fail_test(r#"module foo/bar {}"#, "valid module name")?;
+    fail_test(r#"module foo\bar {}"#, "valid module name")?;
+    fail_test(r#"module foo=bar {}"#, "valid module name")
+}
+
 #[test]
 fn assignment_with_no_var() -> TestResult {
     let cases = [