From 6df88d3c73528adda9ece1d290bec352c86efa64 Mon Sep 17 00:00:00 2001
From: Aaryan Dogra <aaryan.dogra7@gmail.com>
Date: Mon, 27 Apr 2026 21:55:59 +0530
Subject: [PATCH 1/7] Implement no_pad logic for 'N' specifier

Add no_pad handling for specifier ending with 'N'.
---
 src/uu/date/src/format_modifiers.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/uu/date/src/format_modifiers.rs b/src/uu/date/src/format_modifiers.rs
index b77ed78dd65..8022c552f54 100644
--- a/src/uu/date/src/format_modifiers.rs
+++ b/src/uu/date/src/format_modifiers.rs
@@ -411,6 +411,18 @@ fn apply_modifiers(value: &str, parsed: &ParsedSpec<'_>) -> Result<String, Forma
 
     // If no_pad flag is active, suppress all padding and return
     if no_pad {
+        if specifier.ends_with('N') {
+            if let Some(w) = width {
+                let end = w.min(result.len());
+                let truncated = &result[..end];
+                let stripped = truncated.trim_end_matches('0');
+                return Ok(if stripped.is_empty() {
+                    "0".to_string()
+                } else {
+                    stripped.to_string()
+                });
+            }
+        }
         return Ok(strip_default_padding(&result));
     }
 

From 93ad040f88135bb7a878dd5d01b01dcb91c60d76 Mon Sep 17 00:00:00 2001
From: Aaryan <aaryan@example.com>
Date: Wed, 29 Apr 2026 18:21:43 +0530
Subject: [PATCH 2/7] Fix negative width prefix handling for %N format
 specifier

When the dash flag (-) is used with a width on the %N (nanoseconds) format
specifier, the width should be applied to truncate the output without any
additional processing like trimming trailing zeros.

Changes:
- Changed width field from usize to isize to support signed widths
- Updated parsing logic to parse width as isize
- Fixed %N handling in no_pad branch to truncate correctly
- Removed incorrect trailing zero trimming
- Updated effective_width calculation to handle isize widths

Behavior: %-2N now correctly returns first 2 digits of nanoseconds, matching
GNU coreutils behavior.

Fixes: Issue #12001
---
 src/uu/date/src/format_modifiers.rs | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/src/uu/date/src/format_modifiers.rs b/src/uu/date/src/format_modifiers.rs
index 8022c552f54..6198d9167cc 100644
--- a/src/uu/date/src/format_modifiers.rs
+++ b/src/uu/date/src/format_modifiers.rs
@@ -75,9 +75,10 @@ struct ParsedSpec<'a> {
     /// Flag characters from `[_0^#+-]`.
     flags: &'a str,
     /// Explicit width, if present. `None` means no width was specified.
-    /// A value that overflows `usize` is represented as `Some(usize::MAX)` so
+    /// Negative widths (isize) are used when `-` flag precedes the width.
+    /// A value that overflows `isize` is represented as `Some(isize::MAX)` so
     /// the downstream allocation check surfaces it as `FieldWidthTooLarge`.
-    width: Option<usize>,
+    width: Option<isize>,
     /// The specifier itself, including any leading colons (e.g. `Y`, `:z`, `::z`).
     spec: &'a str,
     /// Total byte length of the parsed sequence including the leading `%`.
@@ -110,7 +111,7 @@ fn parse_format_spec(s: &str) -> Option<ParsedSpec<'_>> {
         pos += 1;
     }
     let width = if pos > width_start {
-        Some(s[width_start..pos].parse::<usize>().unwrap_or(usize::MAX))
+        Some(s[width_start..pos].parse::<isize>().unwrap_or(isize::MAX))
     } else {
         None
     };
@@ -413,14 +414,13 @@ fn apply_modifiers(value: &str, parsed: &ParsedSpec<'_>) -> Result<String, Forma
     if no_pad {
         if specifier.ends_with('N') {
             if let Some(w) = width {
-                let end = w.min(result.len());
-                let truncated = &result[..end];
-                let stripped = truncated.trim_end_matches('0');
-                return Ok(if stripped.is_empty() {
-                    "0".to_string()
-                } else {
-                    stripped.to_string()
-                });
+                let w_usize = w as usize;
+                if w_usize > 0 {
+                    let end = w_usize.min(result.len());
+                    let truncated = &result[..end];
+                    // Return truncated nanoseconds without trimming trailing zeros (GNU behavior)
+                    return Ok(truncated.to_string());
+                }
             }
         }
         return Ok(strip_default_padding(&result));
@@ -430,7 +430,10 @@ fn apply_modifiers(value: &str, parsed: &ParsedSpec<'_>) -> Result<String, Forma
     // This applies when _ or 0 flag overrides the default padding character
     // and no explicit width is specified (e.g., %_m, %0e).
     let effective_width = match width {
-        Some(w) => w,
+        Some(w) => {
+            let abs_w = w.abs() as usize;
+            abs_w
+        }
         None if underscore_flag || pad_char != default_pad => get_default_width(specifier),
         None => 0,
     };

From 88f389b7c5328c53dd803f3fdb41b29ae148dcba Mon Sep 17 00:00:00 2001
From: Aaryan <aaryan@example.com>
Date: Thu, 30 Apr 2026 21:02:31 +0530
Subject: [PATCH 3/7] my test

---
 src/uu/date/src/format_modifiers.rs | 39 +++++++++++++++++------------
 1 file changed, 23 insertions(+), 16 deletions(-)

diff --git a/src/uu/date/src/format_modifiers.rs b/src/uu/date/src/format_modifiers.rs
index 6198d9167cc..dcd7b12f5dd 100644
--- a/src/uu/date/src/format_modifiers.rs
+++ b/src/uu/date/src/format_modifiers.rs
@@ -75,7 +75,7 @@ struct ParsedSpec<'a> {
     /// Flag characters from `[_0^#+-]`.
     flags: &'a str,
     /// Explicit width, if present. `None` means no width was specified.
-    /// Negative widths (isize) are used when `-` flag precedes the width.
+    /// Negative widths are used when `-` flag precedes the width.
     /// A value that overflows `isize` is represented as `Some(isize::MAX)` so
     /// the downstream allocation check surfaces it as `FieldWidthTooLarge`.
     width: Option<isize>,
@@ -105,13 +105,18 @@ fn parse_format_spec(s: &str) -> Option<ParsedSpec<'_>> {
     }
     let flags = &s[flags_start..pos];
 
+    // Check if '-' flag is present
+    let has_minus_flag = flags.contains('-');
+
     // Width: zero or more ASCII digits.
     let width_start = pos;
     while pos < bytes.len() && bytes[pos].is_ascii_digit() {
         pos += 1;
     }
     let width = if pos > width_start {
-        Some(s[width_start..pos].parse::<isize>().unwrap_or(isize::MAX))
+        let parsed: isize = s[width_start..pos].parse::<isize>().unwrap_or(isize::MAX);
+        // Make width negative if '-' flag is present
+        Some(if has_minus_flag { -parsed } else { parsed })
     } else {
         None
     };
@@ -344,6 +349,11 @@ fn apply_modifiers(value: &str, parsed: &ParsedSpec<'_>) -> Result<String, Forma
     let specifier = parsed.spec;
     let mut result = value.to_string();
 
+    // Ensure nanoseconds are always zero-padded to 9 digits from the start
+    // if result.len() < 9 {
+    //     result = format!("{:0>9}", result);
+    // }
+
     // Determine default pad character based on specifier type
     // Determine default pad character based on specifier type.
     // Text specifiers (month names, etc.) and numeric specifiers like %e, %k, %l
@@ -412,17 +422,13 @@ fn apply_modifiers(value: &str, parsed: &ParsedSpec<'_>) -> Result<String, Forma
 
     // If no_pad flag is active, suppress all padding and return
     if no_pad {
-        if specifier.ends_with('N') {
             if let Some(w) = width {
-                let w_usize = w as usize;
-                if w_usize > 0 {
-                    let end = w_usize.min(result.len());
-                    let truncated = &result[..end];
-                    // Return truncated nanoseconds without trimming trailing zeros (GNU behavior)
-                    return Ok(truncated.to_string());
-                }
+                let abs_w = w.abs() as usize;
+                let end = abs_w.min(result.len());
+                let truncated = &result[..end];
+                // Return truncated nanoseconds without trimming trailing zeros (GNU behavior)
+                return Ok(truncated.to_string());
             }
-        }
         return Ok(strip_default_padding(&result));
     }
 
@@ -540,7 +546,7 @@ mod tests {
 
     /// Build a `ParsedSpec` for unit-testing `apply_modifiers` without a real
     /// format string.  `len` is set to 0 because these tests never use it.
-    fn spec<'a>(flags: &'a str, width: Option<usize>, spec: &'a str) -> ParsedSpec<'a> {
+    fn spec<'a>(flags: &'a str, width: Option<isize>, spec: &'a str) -> ParsedSpec<'a> {
         ParsedSpec {
             flags,
             width,
@@ -859,11 +865,11 @@ mod tests {
 
     #[test]
     fn test_apply_modifiers_width_too_large() {
-        let err = apply_modifiers("x", &spec("", Some(usize::MAX), "c")).unwrap_err();
+        let err = apply_modifiers("x", &spec("", Some(isize::MAX), "c")).unwrap_err();
         assert!(matches!(
             err,
             FormatError::FieldWidthTooLarge { width, specifier }
-            if width == usize::MAX && specifier == "c"
+            if width == isize::MAX && specifier == "c"
         ));
     }
 
@@ -880,7 +886,7 @@ mod tests {
         assert!(matches!(
             err,
             FormatError::FieldWidthTooLarge { width, specifier }
-            if width == usize::MAX && specifier == "Y"
+            if width == isize::MAX && specifier == "Y"
         ));
     }
 
@@ -954,7 +960,7 @@ mod tests {
     #[test]
     fn test_parse_format_spec() {
         // (input, expected: Some((flags, width, spec, len)) or None)
-        type ParsedTuple = (&'static str, Option<usize>, &'static str, usize);
+        type ParsedTuple = (&'static str, Option<isize>, &'static str, usize);
         let cases: &[(&str, Option<ParsedTuple>)] = &[
             // ---- plain single-letter specifiers ----
             ("%Y", Some(("", None, "Y", 2))),
@@ -1003,6 +1009,7 @@ mod tests {
 
         for (input, expected) in cases {
             let actual = parse_format_spec(input).map(|p| (p.flags, p.width, p.spec, p.len));
+            
             assert_eq!(actual, *expected, "input = {input:?}");
         }
     }

From 864853b17ac5a7c52bd3dd29ce92a2a9664e8df8 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Thu, 30 Apr 2026 15:50:39 +0000
Subject: [PATCH 4/7] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 src/uu/date/src/format_modifiers.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/uu/date/src/format_modifiers.rs b/src/uu/date/src/format_modifiers.rs
index dcd7b12f5dd..66c396716f1 100644
--- a/src/uu/date/src/format_modifiers.rs
+++ b/src/uu/date/src/format_modifiers.rs
@@ -1009,7 +1009,7 @@ mod tests {
 
         for (input, expected) in cases {
             let actual = parse_format_spec(input).map(|p| (p.flags, p.width, p.spec, p.len));
-            
+
             assert_eq!(actual, *expected, "input = {input:?}");
         }
     }

From 86c66d74fff1bafea885c359aec8674f9dd34757 Mon Sep 17 00:00:00 2001
From: Aaryan <aaryan@example.com>
Date: Fri, 1 May 2026 17:26:50 +0530
Subject: [PATCH 5/7] fix-two

---
 src/uu/date/src/format_modifiers.rs | 33 ++++++++++++-----------------
 1 file changed, 14 insertions(+), 19 deletions(-)

diff --git a/src/uu/date/src/format_modifiers.rs b/src/uu/date/src/format_modifiers.rs
index 66c396716f1..23cdeb42df0 100644
--- a/src/uu/date/src/format_modifiers.rs
+++ b/src/uu/date/src/format_modifiers.rs
@@ -44,7 +44,7 @@ pub enum FormatError {
     /// Error from the underlying jiff library
     JiffError(jiff::Error),
     /// Field width calculation overflowed or required allocation failed
-    FieldWidthTooLarge { width: usize, specifier: String },
+    FieldWidthTooLarge { width: isize, specifier: String },
 }
 
 impl fmt::Display for FormatError {
@@ -75,7 +75,6 @@ struct ParsedSpec<'a> {
     /// Flag characters from `[_0^#+-]`.
     flags: &'a str,
     /// Explicit width, if present. `None` means no width was specified.
-    /// Negative widths are used when `-` flag precedes the width.
     /// A value that overflows `isize` is represented as `Some(isize::MAX)` so
     /// the downstream allocation check surfaces it as `FieldWidthTooLarge`.
     width: Option<isize>,
@@ -105,9 +104,6 @@ fn parse_format_spec(s: &str) -> Option<ParsedSpec<'_>> {
     }
     let flags = &s[flags_start..pos];
 
-    // Check if '-' flag is present
-    let has_minus_flag = flags.contains('-');
-
     // Width: zero or more ASCII digits.
     let width_start = pos;
     while pos < bytes.len() && bytes[pos].is_ascii_digit() {
@@ -115,8 +111,7 @@ fn parse_format_spec(s: &str) -> Option<ParsedSpec<'_>> {
     }
     let width = if pos > width_start {
         let parsed: isize = s[width_start..pos].parse::<isize>().unwrap_or(isize::MAX);
-        // Make width negative if '-' flag is present
-        Some(if has_minus_flag { -parsed } else { parsed })
+        Some(parsed)
     } else {
         None
     };
@@ -348,12 +343,7 @@ fn apply_modifiers(value: &str, parsed: &ParsedSpec<'_>) -> Result<String, Forma
     let width = parsed.width;
     let specifier = parsed.spec;
     let mut result = value.to_string();
-
-    // Ensure nanoseconds are always zero-padded to 9 digits from the start
-    // if result.len() < 9 {
-    //     result = format!("{:0>9}", result);
-    // }
-
+    
     // Determine default pad character based on specifier type
     // Determine default pad character based on specifier type.
     // Text specifiers (month names, etc.) and numeric specifiers like %e, %k, %l
@@ -422,13 +412,16 @@ fn apply_modifiers(value: &str, parsed: &ParsedSpec<'_>) -> Result<String, Forma
 
     // If no_pad flag is active, suppress all padding and return
     if no_pad {
+        if specifier.ends_with("N") {
             if let Some(w) = width {
                 let abs_w = w.abs() as usize;
-                let end = abs_w.min(result.len());
-                let truncated = &result[..end];
+                // Truncate from the right by keeping the leftmost characters,
+                let truncated: String = result.chars().take(abs_w).collect();
                 // Return truncated nanoseconds without trimming trailing zeros (GNU behavior)
-                return Ok(truncated.to_string());
+                return Ok(truncated);
             }
+        }
+        // For all other specifiers (and %N without width), just strip padding
         return Ok(strip_default_padding(&result));
     }
 
@@ -483,14 +476,16 @@ fn apply_modifiers(value: &str, parsed: &ParsedSpec<'_>) -> Result<String, Forma
             // Zero padding: sign first, then zeros (e.g., "-0022")
             let sign = result.chars().next().unwrap();
             let rest = &result[1..];
-            let mut padded = try_alloc_padded(result.len(), padding, effective_width, specifier)?;
+            let mut padded =
+                try_alloc_padded(result.len(), padding, effective_width as isize, specifier)?;
             padded.push(sign);
             padded.extend(std::iter::repeat_n('0', padding));
             padded.push_str(rest);
             result = padded;
         } else {
             // Default: pad on the left (e.g., "  -22" or "  1999")
-            let mut padded = try_alloc_padded(result.len(), padding, effective_width, specifier)?;
+            let mut padded =
+                try_alloc_padded(result.len(), padding, effective_width as isize, specifier)?;
             padded.extend(std::iter::repeat_n(pad_char, padding));
             padded.push_str(&result);
             result = padded;
@@ -509,7 +504,7 @@ fn apply_modifiers(value: &str, parsed: &ParsedSpec<'_>) -> Result<String, Forma
 fn try_alloc_padded(
     current_len: usize,
     padding: usize,
-    width: usize,
+    width: isize,
     specifier: &str,
 ) -> Result<String, FormatError> {
     let target_len =

From a6b25aca9abfc7ec67530fe7d35e1fbc071bb4ff Mon Sep 17 00:00:00 2001
From: Aaryan <aaryan@example.com>
Date: Fri, 1 May 2026 19:03:30 +0530
Subject: [PATCH 6/7] fix three

---
 src/uu/date/src/format_modifiers.rs | 39 ++++++++++++-----------------
 1 file changed, 16 insertions(+), 23 deletions(-)

diff --git a/src/uu/date/src/format_modifiers.rs b/src/uu/date/src/format_modifiers.rs
index 23cdeb42df0..30a1d01518d 100644
--- a/src/uu/date/src/format_modifiers.rs
+++ b/src/uu/date/src/format_modifiers.rs
@@ -44,7 +44,7 @@ pub enum FormatError {
     /// Error from the underlying jiff library
     JiffError(jiff::Error),
     /// Field width calculation overflowed or required allocation failed
-    FieldWidthTooLarge { width: isize, specifier: String },
+    FieldWidthTooLarge { width: usize, specifier: String },
 }
 
 impl fmt::Display for FormatError {
@@ -75,9 +75,8 @@ struct ParsedSpec<'a> {
     /// Flag characters from `[_0^#+-]`.
     flags: &'a str,
     /// Explicit width, if present. `None` means no width was specified.
-    /// A value that overflows `isize` is represented as `Some(isize::MAX)` so
-    /// the downstream allocation check surfaces it as `FieldWidthTooLarge`.
-    width: Option<isize>,
+    /// Width overflows are handled naturally by usize parsing.
+    width: Option<usize>,
     /// The specifier itself, including any leading colons (e.g. `Y`, `:z`, `::z`).
     spec: &'a str,
     /// Total byte length of the parsed sequence including the leading `%`.
@@ -110,8 +109,7 @@ fn parse_format_spec(s: &str) -> Option<ParsedSpec<'_>> {
         pos += 1;
     }
     let width = if pos > width_start {
-        let parsed: isize = s[width_start..pos].parse::<isize>().unwrap_or(isize::MAX);
-        Some(parsed)
+        Some(s[width_start..pos].parse::<usize>().unwrap_or(usize::MAX))
     } else {
         None
     };
@@ -412,11 +410,11 @@ fn apply_modifiers(value: &str, parsed: &ParsedSpec<'_>) -> Result<String, Forma
 
     // If no_pad flag is active, suppress all padding and return
     if no_pad {
-        if specifier.ends_with("N") {
+        if specifier.ends_with('N') {
             if let Some(w) = width {
-                let abs_w = w.abs() as usize;
                 // Truncate from the right by keeping the leftmost characters,
-                let truncated: String = result.chars().take(abs_w).collect();
+                // using char iteration to avoid slicing at a non-UTF-8 boundary.
+                let truncated: String = result.chars().take(w).collect();
                 // Return truncated nanoseconds without trimming trailing zeros (GNU behavior)
                 return Ok(truncated);
             }
@@ -429,10 +427,7 @@ fn apply_modifiers(value: &str, parsed: &ParsedSpec<'_>) -> Result<String, Forma
     // This applies when _ or 0 flag overrides the default padding character
     // and no explicit width is specified (e.g., %_m, %0e).
     let effective_width = match width {
-        Some(w) => {
-            let abs_w = w.abs() as usize;
-            abs_w
-        }
+        Some(w) => w,
         None if underscore_flag || pad_char != default_pad => get_default_width(specifier),
         None => 0,
     };
@@ -476,16 +471,14 @@ fn apply_modifiers(value: &str, parsed: &ParsedSpec<'_>) -> Result<String, Forma
             // Zero padding: sign first, then zeros (e.g., "-0022")
             let sign = result.chars().next().unwrap();
             let rest = &result[1..];
-            let mut padded =
-                try_alloc_padded(result.len(), padding, effective_width as isize, specifier)?;
+            let mut padded = try_alloc_padded(result.len(), padding, effective_width, specifier)?;
             padded.push(sign);
             padded.extend(std::iter::repeat_n('0', padding));
             padded.push_str(rest);
             result = padded;
         } else {
             // Default: pad on the left (e.g., "  -22" or "  1999")
-            let mut padded =
-                try_alloc_padded(result.len(), padding, effective_width as isize, specifier)?;
+            let mut padded = try_alloc_padded(result.len(), padding, effective_width, specifier)?;
             padded.extend(std::iter::repeat_n(pad_char, padding));
             padded.push_str(&result);
             result = padded;
@@ -504,7 +497,7 @@ fn apply_modifiers(value: &str, parsed: &ParsedSpec<'_>) -> Result<String, Forma
 fn try_alloc_padded(
     current_len: usize,
     padding: usize,
-    width: isize,
+    width: usize,
     specifier: &str,
 ) -> Result<String, FormatError> {
     let target_len =
@@ -541,7 +534,7 @@ mod tests {
 
     /// Build a `ParsedSpec` for unit-testing `apply_modifiers` without a real
     /// format string.  `len` is set to 0 because these tests never use it.
-    fn spec<'a>(flags: &'a str, width: Option<isize>, spec: &'a str) -> ParsedSpec<'a> {
+    fn spec<'a>(flags: &'a str, width: Option<usize>, spec: &'a str) -> ParsedSpec<'a> {
         ParsedSpec {
             flags,
             width,
@@ -860,11 +853,11 @@ mod tests {
 
     #[test]
     fn test_apply_modifiers_width_too_large() {
-        let err = apply_modifiers("x", &spec("", Some(isize::MAX), "c")).unwrap_err();
+        let err = apply_modifiers("x", &spec("", Some(usize::MAX), "c")).unwrap_err();
         assert!(matches!(
             err,
             FormatError::FieldWidthTooLarge { width, specifier }
-            if width == isize::MAX && specifier == "c"
+            if width == usize::MAX && specifier == "c"
         ));
     }
 
@@ -881,7 +874,7 @@ mod tests {
         assert!(matches!(
             err,
             FormatError::FieldWidthTooLarge { width, specifier }
-            if width == isize::MAX && specifier == "Y"
+            if width == usize::MAX && specifier == "Y"
         ));
     }
 
@@ -955,7 +948,7 @@ mod tests {
     #[test]
     fn test_parse_format_spec() {
         // (input, expected: Some((flags, width, spec, len)) or None)
-        type ParsedTuple = (&'static str, Option<isize>, &'static str, usize);
+        type ParsedTuple = (&'static str, Option<usize>, &'static str, usize);
         let cases: &[(&str, Option<ParsedTuple>)] = &[
             // ---- plain single-letter specifiers ----
             ("%Y", Some(("", None, "Y", 2))),

From b241b1c380eda235f022411d584dbe688a4fb714 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Fri, 1 May 2026 13:34:44 +0000
Subject: [PATCH 7/7] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 src/uu/date/src/format_modifiers.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/uu/date/src/format_modifiers.rs b/src/uu/date/src/format_modifiers.rs
index 30a1d01518d..3e1071ef636 100644
--- a/src/uu/date/src/format_modifiers.rs
+++ b/src/uu/date/src/format_modifiers.rs
@@ -341,7 +341,7 @@ fn apply_modifiers(value: &str, parsed: &ParsedSpec<'_>) -> Result<String, Forma
     let width = parsed.width;
     let specifier = parsed.spec;
     let mut result = value.to_string();
-    
+
     // Determine default pad character based on specifier type
     // Determine default pad character based on specifier type.
     // Text specifiers (month names, etc.) and numeric specifiers like %e, %k, %l