Retain trailing non-whitespace separators

When there are more fields than variables, the last variable receives
all remaining fields, including the field separators, but not trailing
whitespace separators. This is the behavior required by POSIX.

yash-builtin/src/read.rs

@@ -31,8 +31,8 @@
 //! read to produce as many fields as there are variables. If there are fewer
 //! fields than variables, the remaining variables are set to empty strings. If
 //! there are more fields than variables, the last variable receives all
-//! remaining fields, including the intermediate (but not trailing) field
-//! separators.
+//! remaining fields, including the field separators, but not trailing
+//! whitespace separators.
 //!
 //! ## Escaping
 //!

yash-builtin/src/read/assigning.rs

@@ -24,6 +24,7 @@ use yash_env::Env;
 use yash_semantics::expansion::attr::AttrChar;
 use yash_semantics::expansion::attr_strip::Strip as _;
 use yash_semantics::expansion::quote_removal::skip_quotes;
+use yash_semantics::expansion::split::Class;
 use yash_semantics::expansion::split::Ifs;
 use yash_syntax::source::pretty::Message;
 use yash_syntax::source::pretty::MessageBase as _;
@@ -44,9 +45,9 @@ pub fn to_message(errors: &[Error]) -> Option<Message> {
 ///
 /// This function performs field splitting on the text and assigns the resulting
 /// fields to the variables. When there are more fields than variables, the last
-/// variable receives all remaining fields, including the intermediate (but not
-/// trailing) field separators. When there are fewer fields than variables, the
-/// remaining variables are set to empty strings.
+/// variable receives all remaining fields, including the field separators, but
+/// not trailing whitespace separators. When there are fewer fields than
+/// variables, the remaining variables are set to empty strings.
 ///
 /// The return value is a vector of errors that occurred while assigning the
 /// variables. The vector is empty if no error occurred.
@@ -79,9 +80,16 @@ pub fn assign(
     // Assign the last
     let range = match ranges.next() {
         None => 0..0,
-        Some(range) => match ranges.last() {
+        Some(range) => match ranges.next() {
             None => range,
-            Some(range_2) => range.start..range_2.end,
+            Some(_range) => {
+                let end = text
+                    .iter()
+                    .rposition(|&c| ifs.classify_attr(c) != Class::IfsWhitespace)
+                    .unwrap()
+                    + 1;
+                range.start..end
+            }
         },
     };
     let last_result = assign_one(env, last_variable, &text[range]);
@@ -291,7 +299,6 @@ mod tests {
     }
 
     #[test]
-    #[ignore = "to be implemented"]
     fn non_default_ifs_delimiting_last_field_extra() {
         let mut env = Env::new_virtual();
         env.get_or_create_variable("IFS", Scope::Global)

yash-semantics/src/expansion/split/ifs.rs

@@ -16,6 +16,8 @@
 
 //! IFS parser
 
+use crate::expansion::attr::AttrChar;
+use crate::expansion::attr::Origin;
 use std::borrow::Cow;
 
 /// Type of characters that affect field splitting
@@ -185,6 +187,16 @@ impl Ifs<'_> {
             Class::NonIfs
         }
     }
+
+    /// Returns the type of the attributed character.
+    #[must_use]
+    pub fn classify_attr(&self, c: AttrChar) -> Class {
+        if c.is_quoted || c.is_quoting || c.origin != Origin::SoftExpansion {
+            Class::NonIfs
+        } else {
+            self.classify(c.value)
+        }
+    }
 }
 
 #[cfg(test)]

yash-semantics/src/expansion/split/ranges.rs

@@ -17,21 +17,11 @@
 //! Extracting ranges of split fields
 
 use super::super::attr::AttrChar;
-use super::super::attr::Origin;
-use super::ifs::Class;
 use super::ifs::Class::*;
 use super::ifs::Ifs;
 use std::iter::FusedIterator;
 use std::ops::Range;
 
-fn classify(c: AttrChar, ifs: &Ifs) -> Class {
-    if c.is_quoted || c.is_quoting || c.origin != Origin::SoftExpansion {
-        NonIfs
-    } else {
-        ifs.classify(c.value)
-    }
-}
-
 /// State of a field-splitting iterator
 #[derive(Clone, Copy, Debug, Default, Eq, Hash, PartialEq)]
 enum State {
@@ -83,7 +73,7 @@ where
     fn next(&mut self) -> Option<Range<usize>> {
         while let Some(state) = self.state {
             let index = self.next_index;
-            let class = self.inner.next().map(|c| classify(c, self.ifs));
+            let class = self.inner.next().map(|c| self.ifs.classify_attr(c));
             self.next_index += 1;
 
             let (next_state, field_range) = match (state, class) {
@@ -148,6 +138,7 @@ impl<I> FusedIterator for Ranges<'_, I> where I: Iterator<Item = AttrChar> {}
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::expansion::attr::Origin;
 
     fn attr_chars(s: &str) -> impl Iterator<Item = AttrChar> + '_ {
         s.chars().map(|c| AttrChar {