Add Value::coerce_str (#11885)

# Description
Following #11851, this PR adds one final conversion function for
`Value`. `Value::coerce_str` takes a `&Value` and converts it to a
`Cow<str>`, creating an owned `String` for types that needed converting.
Otherwise, it returns a borrowed `str` for `String` and `Binary`
`Value`s which avoids a clone/allocation. Where possible, `coerce_str`
and `coerce_into_string` should be used instead of `coerce_string`,
since `coerce_string` always allocates a new `String`.

crates/nu-cli/src/completions/command_completions.rs

@@ -43,9 +43,9 @@ impl CommandCompletion {
         if let Some(paths) = paths {
             if let Ok(paths) = paths.as_list() {
                 for path in paths {
-                    let path = path.coerce_string().unwrap_or_default();
+                    let path = path.coerce_str().unwrap_or_default();
 
-                    if let Ok(mut contents) = std::fs::read_dir(path) {
+                    if let Ok(mut contents) = std::fs::read_dir(path.as_ref()) {
                         while let Some(Ok(item)) = contents.next() {
                             if self.engine_state.config.max_external_completion_results
                                 > executables.len() as i64

crates/nu-cli/src/eval_cmds.rs

@@ -28,7 +28,7 @@ pub fn evaluate_commands(
     let (block, delta) = {
         if let Some(ref t_mode) = table_mode {
             let mut config = engine_state.get_config().clone();
-            config.table_mode = t_mode.coerce_string()?.parse().unwrap_or_default();
+            config.table_mode = t_mode.coerce_str()?.parse().unwrap_or_default();
             engine_state.set_config(config);
         }
 
@@ -59,7 +59,7 @@ pub fn evaluate_commands(
         Ok(pipeline_data) => {
             let mut config = engine_state.get_config().clone();
             if let Some(t_mode) = table_mode {
-                config.table_mode = t_mode.coerce_string()?.parse().unwrap_or_default();
+                config.table_mode = t_mode.coerce_str()?.parse().unwrap_or_default();
             }
             crate::eval_file::print_table_or_error(engine_state, stack, pipeline_data, &mut config)
         }

crates/nu-cli/src/reedline_config.rs

@@ -459,9 +459,7 @@ pub(crate) fn add_ide_menu(
         };
 
         ide_menu = match extract_value("description_mode", val, span) {
-            Ok(description_mode) => {
-                let description_mode_str = description_mode.coerce_string()?;
-                match description_mode_str.as_str() {
+            Ok(description_mode) => match description_mode.coerce_str()?.as_ref() {
                 "left" => ide_menu.with_description_mode(DescriptionMode::Left),
                 "right" => ide_menu.with_description_mode(DescriptionMode::Right),
                 "prefer_right" => ide_menu.with_description_mode(DescriptionMode::PreferRight),
@@ -472,8 +470,7 @@ pub(crate) fn add_ide_menu(
                         span: description_mode.span(),
                     });
                 }
-                }
-            }
+            },
             Err(_) => ide_menu,
         };
 

crates/nu-color-config/src/matching_brackets_style.rs

@@ -6,7 +6,7 @@ pub fn get_matching_brackets_style(default_style: Style, conf: &Config) -> Style
     const MATCHING_BRACKETS_CONFIG_KEY: &str = "shape_matching_brackets";
 
     match conf.color_config.get(MATCHING_BRACKETS_CONFIG_KEY) {
-        Some(int_color) => match int_color.coerce_string() {
+        Some(int_color) => match int_color.coerce_str() {
             Ok(int_color) => merge_styles(default_style, lookup_ansi_color_style(&int_color)),
             Err(_) => default_style,
         },

crates/nu-command/src/conversions/into/datetime.rs

@@ -262,7 +262,7 @@ fn action(input: &Value, args: &Arguments, head: Span) -> Value {
     // Let's try dtparse first
     if matches!(input, Value::String { .. }) && dateformat.is_none() {
         let span = input.span();
-        if let Ok(input_val) = input.coerce_string() {
+        if let Ok(input_val) = input.coerce_str() {
             match parse_date_from_string(&input_val, span) {
                 Ok(date) => return Value::date(date, span),
                 Err(_) => {

crates/nu-command/src/conversions/into/value.rs

@@ -142,7 +142,7 @@ impl Iterator for UpdateCellIterator {
 // for a particular datatype. If it does, it will convert the cell to that datatype.
 fn process_cell(val: Value, display_as_filesizes: bool, span: Span) -> Result<Value, ShellError> {
     // step 1: convert value to string
-    let val_str = val.coerce_string().unwrap_or_default();
+    let val_str = val.coerce_str().unwrap_or_default();
 
     // step 2: bounce string up against regexes
     if BOOLEAN_RE.is_match(&val_str) {
@@ -189,7 +189,7 @@ fn process_cell(val: Value, display_as_filesizes: bool, span: Span) -> Result<Va
             Ok(Value::int(ival, span))
         }
     } else if INTEGER_WITH_DELIMS_RE.is_match(&val_str) {
-        let mut val_str = val_str;
+        let mut val_str = val_str.into_owned();
         val_str.retain(|x| !['_', ','].contains(&x));
 
         let ival = val_str

crates/nu-command/src/filters/move_.rs

@@ -222,9 +222,7 @@ fn move_record_columns(
 
     // Find indices of columns to be moved
     for column in columns.iter() {
-        let column_str = column.coerce_string()?;
-
-        if let Some(idx) = record.index_of(&column_str) {
+        if let Some(idx) = record.index_of(&column.coerce_str()?) {
             column_idx.push(idx);
         } else {
             return Err(ShellError::GenericError {

crates/nu-command/src/filters/sort.rs

@@ -288,7 +288,7 @@ pub fn sort(
                             .unwrap_or(Ordering::Equal)
                     }
                 } else if natural {
-                    match (a.coerce_string(), b.coerce_string()) {
+                    match (a.coerce_str(), b.coerce_str()) {
                         (Ok(left), Ok(right)) => compare_str(left, right),
                         _ => Ordering::Equal,
                     }

crates/nu-command/src/filters/transpose.rs

@@ -194,7 +194,7 @@ pub fn transpose(
                 match &i.get_data_by_key(desc) {
                     Some(x) => {
                         if let Ok(s) = x.coerce_string() {
-                            headers.push(s.to_string());
+                            headers.push(s);
                         } else {
                             return Err(ShellError::GenericError {
                                 error: "Header row needs string headers".into(),

crates/nu-command/src/network/url/build_query.rs

@@ -72,7 +72,7 @@ fn to_url(input: PipelineData, head: Span) -> Result<PipelineData, ShellError> {
                     for (k, v) in val {
                         match v.coerce_string() {
                             Ok(s) => {
-                                row_vec.push((k.clone(), s.to_string()));
+                                row_vec.push((k.clone(), s));
                             }
                             _ => {
                                 return Err(ShellError::UnsupportedInput {

crates/nu-command/src/path/join.rs

@@ -262,29 +262,29 @@ fn merge_record(record: &Record, head: Span, span: Span) -> Result<PathBuf, Shel
 
     #[cfg(windows)]
     if let Some(val) = record.get("prefix") {
-        let p = val.coerce_string()?;
+        let p = val.coerce_str()?;
         if !p.is_empty() {
-            result.push(p);
+            result.push(p.as_ref());
         }
     }
 
     if let Some(val) = record.get("parent") {
-        let p = val.coerce_string()?;
+        let p = val.coerce_str()?;
         if !p.is_empty() {
-            result.push(p);
+            result.push(p.as_ref());
         }
     }
 
     let mut basename = String::new();
     if let Some(val) = record.get("stem") {
-        let p = val.coerce_string()?;
+        let p = val.coerce_str()?;
         if !p.is_empty() {
             basename.push_str(&p);
         }
     }
 
     if let Some(val) = record.get("extension") {
-        let p = val.coerce_string()?;
+        let p = val.coerce_str()?;
         if !p.is_empty() {
             basename.push('.');
             basename.push_str(&p);

crates/nu-command/src/platform/ansi/ansi_.rs

@@ -738,9 +738,9 @@ fn heavy_lifting(code: Value, escape: bool, osc: bool, call: &Call) -> Result<St
         });
     }
     let code_string = if param_is_string {
-        code.coerce_string().expect("error getting code as string")
+        code.coerce_str().expect("error getting code as string")
     } else {
-        "".to_string()
+        "".into()
     };
     let param_is_valid_string = param_is_string && !code_string.is_empty();
     if (escape || osc) && (param_is_valid_string) {

crates/nu-command/src/sort_utils.rs

@@ -150,7 +150,7 @@ pub fn sort(
                             .unwrap_or(Ordering::Equal)
                     }
                 } else if natural {
-                    match (a.coerce_string(), b.coerce_string()) {
+                    match (a.coerce_str(), b.coerce_str()) {
                         (Ok(left), Ok(right)) => compare_str(left, right),
                         _ => Ordering::Equal,
                     }

crates/nu-command/src/stor/create.rs

@@ -89,7 +89,7 @@ fn process(
                     new_table_name
                 );
                 for (column_name, column_datatype) in record {
-                    match column_datatype.coerce_string()?.as_str() {
+                    match column_datatype.coerce_str()?.as_ref() {
                         "int" => {
                             create_stmt.push_str(&format!("{} INTEGER, ", column_name));
                         }

crates/nu-command/src/strings/detect_columns.rs

@@ -226,7 +226,7 @@ fn detect_columns(
                 .iter()
                 .take(end_index)
                 .skip(start_index)
-                .map(|v| v.coerce_string().unwrap_or_default())
+                .map(|v| v.coerce_str().unwrap_or_default())
                 .join(" ");
             let binding = Value::string(combined, Span::unknown());
             let last_seg = vals.split_off(end_index);

crates/nu-command/src/strings/split/chars.rs

@@ -124,7 +124,7 @@ fn split_chars_helper(v: &Value, name: Span, graphemes: bool) -> Value {
         Value::Error { error, .. } => Value::error(*error.clone(), span),
         v => {
             let v_span = v.span();
-            if let Ok(s) = v.coerce_string() {
+            if let Ok(s) = v.coerce_str() {
                 Value::list(
                     if graphemes {
                         s.graphemes(true)

crates/nu-command/src/strings/split/column.rs

@@ -148,7 +148,7 @@ fn split_column_helper(
     collapse_empty: bool,
     head: Span,
 ) -> Vec<Value> {
-    if let Ok(s) = v.coerce_string() {
+    if let Ok(s) = v.coerce_str() {
         let split_result: Vec<_> = separator
             .split(&s)
             .filter(|x| !(collapse_empty && x.is_empty()))

crates/nu-command/src/strings/split/list.rs

@@ -160,7 +160,7 @@ enum Matcher {
 impl Matcher {
     pub fn new(regex: bool, lhs: Value) -> Result<Self, ShellError> {
         if regex {
-            Ok(Matcher::Regex(Regex::new(&lhs.coerce_string()?).map_err(
+            Ok(Matcher::Regex(Regex::new(&lhs.coerce_str()?).map_err(
                 |e| ShellError::GenericError {
                     error: "Error with regular expression".into(),
                     msg: e.to_string(),
@@ -180,7 +180,7 @@ impl Matcher {
     pub fn compare(&self, rhs: &Value) -> Result<bool, ShellError> {
         Ok(match self {
             Matcher::Regex(regex) => {
-                if let Ok(rhs_str) = rhs.coerce_string() {
+                if let Ok(rhs_str) = rhs.coerce_str() {
                     regex.is_match(&rhs_str)
                 } else {
                     false

crates/nu-command/src/strings/split/row.rs

@@ -152,7 +152,7 @@ fn split_row_helper(v: &Value, regex: &Regex, max_split: Option<usize>, name: Sp
         v => {
             let v_span = v.span();
 
-            if let Ok(s) = v.coerce_string() {
+            if let Ok(s) = v.coerce_str() {
                 match max_split {
                     Some(max_split) => regex
                         .splitn(&s, max_split)

crates/nu-command/src/strings/split/words.rs

@@ -158,7 +158,7 @@ fn split_words_helper(v: &Value, word_length: Option<usize>, span: Span, graphem
         Value::Error { error, .. } => Value::error(*error.clone(), v_span),
         v => {
             let v_span = v.span();
-            if let Ok(s) = v.coerce_string() {
+            if let Ok(s) = v.coerce_str() {
                 // let splits = s.unicode_words();
                 // let words = trim_to_words(s);
                 // let words: Vec<&str> = s.split_whitespace().collect();

crates/nu-engine/src/env.rs

@@ -110,10 +110,10 @@ pub fn env_to_string(
                         Value::List { vals, .. } => {
                             let paths = vals
                                 .iter()
-                                .map(|v| v.coerce_string())
+                                .map(Value::coerce_str)
                                 .collect::<Result<Vec<_>, _>>()?;
 
-                            match std::env::join_paths(paths) {
+                            match std::env::join_paths(paths.iter().map(AsRef::as_ref)) {
                                 Ok(p) => Ok(p.to_string_lossy().to_string()),
                                 Err(_) => Err(ShellError::EnvVarNotAString {
                                     envvar_name: env_name.to_string(),

crates/nu-explore/src/pager/mod.rs

@@ -1008,7 +1008,7 @@ fn cmd_input_key_event(buf: &mut CommandBuf, key: &KeyEvent) -> bool {
 }
 
 fn value_as_style(style: &mut nu_ansi_term::Style, value: &Value) -> bool {
-    match value.coerce_string() {
+    match value.coerce_str() {
         Ok(s) => {
             *style = lookup_ansi_color_style(&s);
             true

crates/nu-explore/src/views/record/mod.rs

@@ -331,8 +331,8 @@ impl View for RecordView<'_> {
         if let Some(hm) = cfg.config.get("table").and_then(create_map) {
             self.theme = theme_from_config(&hm);
 
-            if let Some(orientation) = hm.get("orientation").and_then(|v| v.coerce_string().ok()) {
-                let orientation = match orientation.as_str() {
+            if let Some(orientation) = hm.get("orientation").and_then(|v| v.coerce_str().ok()) {
+                let orientation = match orientation.as_ref() {
                     "left" => Some(Orientation::Left),
                     "top" => Some(Orientation::Top),
                     _ => None,
@@ -859,7 +859,7 @@ fn config_get_bool(config: &ConfigMap, key: &str, default: bool) -> bool {
 fn config_get_usize(config: &ConfigMap, key: &str, default: usize) -> usize {
     config
         .get(key)
-        .and_then(|v| v.coerce_string().ok())
+        .and_then(|v| v.coerce_str().ok())
         .and_then(|s| s.parse::<usize>().ok())
         .unwrap_or(default)
 }

crates/nu-protocol/src/config/helper.rs

@@ -15,7 +15,7 @@ pub(super) fn process_string_enum<T, E>(
     E: Display,
 {
     let span = value.span();
-    if let Ok(v) = value.coerce_string() {
+    if let Ok(v) = value.coerce_str() {
         match v.parse() {
             Ok(format) => {
                 *config_point = format;

crates/nu-protocol/src/config/mod.rs

@@ -539,7 +539,7 @@ impl Value {
                                     process_bool_config(value, &mut errors, &mut config.filesize_metric);
                                 }
                                 "format" => {
-                                    if let Ok(v) = value.coerce_string() {
+                                    if let Ok(v) = value.coerce_str() {
                                         config.filesize_format = v.to_lowercase();
                                     } else {
                                         report_invalid_value("should be a string", span, &mut errors);

crates/nu-protocol/src/config/table.rs

@@ -272,7 +272,7 @@ pub(super) fn try_parse_trim_strategy(
 }
 
 fn try_parse_trim_methodology(value: &Value) -> Option<TrimStrategy> {
-    if let Ok(value) = value.coerce_string() {
+    if let Ok(value) = value.coerce_str() {
         match value.to_lowercase().as_str() {
         "wrapping" => {
             return Some(TrimStrategy::Wrap {

crates/nu-protocol/src/value/mod.rs

@@ -356,7 +356,7 @@ impl Value {
         }
     }
 
-    /// Returns this `Value` converted to a `String` or an error if it cannot be converted
+    /// Returns this `Value` converted to a `str` or an error if it cannot be converted
     ///
     /// Only the following `Value` cases will return an `Ok` result:
     /// - `Int`
@@ -365,9 +365,56 @@ impl Value {
     /// - `Binary` (only if valid utf-8)
     /// - `Date`
     ///
-    /// Prefer [`coerce_into_string`](Self::coerce_into_string)
+    /// ```
+    /// # use nu_protocol::Value;
+    /// for val in Value::test_values() {
+    ///     assert_eq!(
+    ///         matches!(
+    ///             val,
+    ///             Value::Int { .. }
+    ///                 | Value::Float { .. }
+    ///                 | Value::String { .. }
+    ///                 | Value::Binary { .. }
+    ///                 | Value::Date { .. }
+    ///         ),
+    ///         val.coerce_str().is_ok(),
+    ///     );
+    /// }
+    /// ```
+    pub fn coerce_str(&self) -> Result<Cow<str>, ShellError> {
+        match self {
+            Value::Int { val, .. } => Ok(Cow::Owned(val.to_string())),
+            Value::Float { val, .. } => Ok(Cow::Owned(val.to_string())),
+            Value::String { val, .. } => Ok(Cow::Borrowed(val)),
+            Value::Binary { val, .. } => match std::str::from_utf8(val) {
+                Ok(s) => Ok(Cow::Borrowed(s)),
+                Err(_) => self.cant_convert_to("string"),
+            },
+            Value::Date { val, .. } => Ok(Cow::Owned(
+                val.to_rfc3339_opts(chrono::SecondsFormat::Millis, true),
+            )),
+            val => val.cant_convert_to("string"),
+        }
+    }
+
+    /// Returns this `Value` converted to a `String` or an error if it cannot be converted
+    ///
+    /// # Note
+    /// This function is equivalent to `value.coerce_str().map(Cow::into_owned)`
+    /// which might allocate a new `String`.
+    ///
+    /// To avoid this allocation, prefer [`coerce_str`](Self::coerce_str)
+    /// if you do not need an owned `String`,
+    /// or [`coerce_into_string`](Self::coerce_into_string)
     /// if you do not need to keep the original `Value` around.
     ///
+    /// Only the following `Value` cases will return an `Ok` result:
+    /// - `Int`
+    /// - `Float`
+    /// - `String`
+    /// - `Binary` (only if valid utf-8)
+    /// - `Date`
+    ///
     /// ```
     /// # use nu_protocol::Value;
     /// for val in Value::test_values() {
@@ -385,17 +432,7 @@ impl Value {
     /// }
     /// ```
     pub fn coerce_string(&self) -> Result<String, ShellError> {
-        match self {
-            Value::Int { val, .. } => Ok(val.to_string()),
-            Value::Float { val, .. } => Ok(val.to_string()),
-            Value::String { val, .. } => Ok(val.clone()),
-            Value::Binary { val, .. } => match std::str::from_utf8(val) {
-                Ok(s) => Ok(s.to_string()),
-                Err(_) => self.cant_convert_to("string"),
-            },
-            Value::Date { val, .. } => Ok(val.to_rfc3339_opts(chrono::SecondsFormat::Millis, true)),
-            val => val.cant_convert_to("string"),
-        }
+        self.coerce_str().map(Cow::into_owned)
     }
 
     /// Returns this `Value` converted to a `String` or an error if it cannot be converted
@@ -570,13 +607,13 @@ impl Value {
 
     /// Returns this `Value` as a `u8` slice or an error if it cannot be converted
     ///
+    /// Prefer [`coerce_into_binary`](Self::coerce_into_binary)
+    /// if you do not need to keep the original `Value` around.
+    ///
     /// Only the following `Value` cases will return an `Ok` result:
     /// - `Binary`
     /// - `String`
     ///
-    /// Prefer [`coerce_into_binary`](Self::coerce_into_binary)
-    /// if you do not need to keep the original `Value` around.
-    ///
     /// ```
     /// # use nu_protocol::Value;
     /// for val in Value::test_values() {

crates/nu_plugin_formats/src/from/ics.rs

@@ -9,7 +9,7 @@ pub const CMD_NAME: &str = "from ics";
 
 pub fn from_ics_call(call: &EvaluatedCall, input: &Value) -> Result<Value, LabeledError> {
     let span = input.span();
-    let input_string = input.coerce_string()?;
+    let input_string = input.coerce_str()?;
     let head = call.head;
 
     let input_string = input_string

crates/nu_plugin_formats/src/from/ini.rs

@@ -5,7 +5,7 @@ pub const CMD_NAME: &str = "from ini";
 
 pub fn from_ini_call(call: &EvaluatedCall, input: &Value) -> Result<Value, LabeledError> {
     let span = input.span();
-    let input_string = input.coerce_string()?;
+    let input_string = input.coerce_str()?;
     let head = call.head;
 
     let ini_config: Result<ini::Ini, ini::ParseError> = ini::Ini::load_from_str(&input_string);

crates/nu_plugin_formats/src/from/vcf.rs

@@ -8,7 +8,7 @@ pub const CMD_NAME: &str = "from vcf";
 
 pub fn from_vcf_call(call: &EvaluatedCall, input: &Value) -> Result<Value, LabeledError> {
     let span = input.span();
-    let input_string = input.coerce_string()?;
+    let input_string = input.coerce_str()?;
     let head = call.head;
 
     let input_string = input_string

crates/nu_plugin_query/src/query_json.rs

@@ -8,8 +8,8 @@ pub fn execute_json_query(
     input: &Value,
     query: Option<Spanned<String>>,
 ) -> Result<Value, LabeledError> {
-    let input_string = match &input.coerce_string() {
-        Ok(s) => s.clone(),
+    let input_string = match input.coerce_str() {
+        Ok(s) => s,
         Err(e) => {
             return Err(LabeledError {
                 span: Some(call.head),

crates/nu_plugin_query/src/query_web.rs

@@ -332,15 +332,15 @@ mod tests {
             Span::test_data(),
         );
         let out = item
-            .as_list()
+            .into_list()
             .unwrap()
-            .iter()
+            .into_iter()
             .map(|matches| {
                 matches
-                    .as_list()
+                    .into_list()
                     .unwrap()
-                    .iter()
-                    .map(|text_nodes| text_nodes.coerce_string().unwrap())
+                    .into_iter()
+                    .map(|text_nodes| text_nodes.coerce_into_string().unwrap())
                     .collect::<Vec<String>>()
             })
             .collect::<Vec<Vec<String>>>();

crates/nu_plugin_query/src/query_xml.rs

@@ -21,7 +21,7 @@ pub fn execute_xpath_query(
     };
 
     let xpath = build_xpath(query_string, span)?;
-    let input_string = input.coerce_string()?;
+    let input_string = input.coerce_str()?;
     let package = parser::parse(&input_string);
 
     if package.is_err() {

src/test_bins.rs

@@ -325,9 +325,9 @@ pub fn nu_repl() {
 
         if let Some(cwd) = stack.get_env_var(&engine_state, "PWD") {
             let path = cwd
-                .coerce_string()
+                .coerce_str()
                 .unwrap_or_else(|err| outcome_err(&engine_state, &err));
-            let _ = std::env::set_current_dir(path);
+            let _ = std::env::set_current_dir(path.as_ref());
             engine_state.add_env_var("PWD".into(), cwd);
         }
     }