Use Value::coerce_bool in into bool (#14731)

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# Description
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I realized that the `into bool` command somehow implements a conversion
into a boolean value which was very similar to my implementation of
~`Value::as_env_bool`~ `Value::coerce_bool`. To streamline that behavior
a bit, I replaced most of the implementation of `into bool` with my
~`Value::as_env_bool`~ `Value::coerce_bool` method.

Also I added a new flag called `--relaxed` which lets the command behave
more closely to the ~`Value::as_env_bool`~ `Value::coerce_bool` method
as it allows null values and is more loose to strings. ~Which now begs
the question, should I rename `Value::as_env_bool` just to
`Value::coerce_bool` which would fit the `Value::coerce_str` method
name?~ (Renamed that.)

# User-Facing Changes
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The `into bool` command behaves the same but with `--relaxed` you can
also throw a `null` or some more strings at it which makes it more
ergonomic for env conversions.

# Tests + Formatting
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I added some more tests to see that the strict handling works and added
some more examples to the command to showcase the `--relaxed` flag which
also gets tested.

- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`

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@Bahex mentioned in #14704 that it broke the zoxide script, this PR
should help to fix the issue.

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

@@ -1,4 +1,4 @@
-use nu_cmd_base::input_handler::{operate, CellPathOnlyArgs};
+use nu_cmd_base::input_handler::{operate, CmdArgument};
 use nu_engine::command_prelude::*;
 
 #[derive(Clone)]
@@ -16,10 +16,16 @@ impl Command for SubCommand {
                 (Type::Number, Type::Bool),
                 (Type::String, Type::Bool),
                 (Type::Bool, Type::Bool),
+                (Type::Nothing, Type::Bool),
                 (Type::List(Box::new(Type::Any)), Type::table()),
                 (Type::table(), Type::table()),
                 (Type::record(), Type::record()),
             ])
+            .switch(
+                "relaxed",
+                "Relaxes conversion to also allow null and any strings.",
+                None,
+            )
             .allow_variants_without_examples(true)
             .rest(
                 "rest",
@@ -44,7 +50,10 @@ impl Command for SubCommand {
         call: &Call,
         input: PipelineData,
     ) -> Result<PipelineData, ShellError> {
-        into_bool(engine_state, stack, call, input)
+        let relaxed = call
+            .has_flag(engine_state, stack, "relaxed")
+            .unwrap_or(false);
+        into_bool(engine_state, stack, call, input, relaxed)
     }
 
     fn examples(&self) -> Vec<Example> {
@@ -95,22 +104,47 @@ impl Command for SubCommand {
                 example: "'true' | into bool",
                 result: Some(Value::test_bool(true)),
             },
+            Example {
+                description: "interpret a null as false",
+                example: "null | into bool --relaxed",
+                result: Some(Value::test_bool(false)),
+            },
+            Example {
+                description: "interpret any non-false, non-zero string as true",
+                example: "'something' | into bool --relaxed",
+                result: Some(Value::test_bool(true)),
+            },
         ]
     }
 }
 
+struct IntoBoolCmdArgument {
+    cell_paths: Option<Vec<CellPath>>,
+    relaxed: bool,
+}
+
+impl CmdArgument for IntoBoolCmdArgument {
+    fn take_cell_paths(&mut self) -> Option<Vec<CellPath>> {
+        self.cell_paths.take()
+    }
+}
+
 fn into_bool(
     engine_state: &EngineState,
     stack: &mut Stack,
     call: &Call,
     input: PipelineData,
+    relaxed: bool,
 ) -> Result<PipelineData, ShellError> {
-    let cell_paths: Vec<CellPath> = call.rest(engine_state, stack, 0)?;
-    let args = CellPathOnlyArgs::from(cell_paths);
+    let cell_paths = Some(call.rest(engine_state, stack, 0)?).filter(|v| !v.is_empty());
+    let args = IntoBoolCmdArgument {
+        cell_paths,
+        relaxed,
+    };
     operate(action, args, input, call.head, engine_state.signals())
 }
 
-fn string_to_boolean(s: &str, span: Span) -> Result<bool, ShellError> {
+fn strict_string_to_boolean(s: &str, span: Span) -> Result<bool, ShellError> {
     match s.trim().to_ascii_lowercase().as_str() {
         "true" => Ok(true),
         "false" => Ok(false),
@@ -132,26 +166,31 @@ fn string_to_boolean(s: &str, span: Span) -> Result<bool, ShellError> {
     }
 }
 
-fn action(input: &Value, _args: &CellPathOnlyArgs, span: Span) -> Value {
-    match input {
-        Value::Bool { .. } => input.clone(),
-        Value::Int { val, .. } => Value::bool(*val != 0, span),
-        Value::Float { val, .. } => Value::bool(val.abs() >= f64::EPSILON, span),
-        Value::String { val, .. } => match string_to_boolean(val, span) {
+fn action(input: &Value, args: &IntoBoolCmdArgument, span: Span) -> Value {
+    let err = || {
+        Value::error(
+            ShellError::OnlySupportsThisInputType {
+                exp_input_type: "bool, int, float or string".into(),
+                wrong_type: input.get_type().to_string(),
+                dst_span: span,
+                src_span: input.span(),
+            },
+            span,
+        )
+    };
+
+    match (input, args.relaxed) {
+        (Value::Error { .. } | Value::Bool { .. }, _) => input.clone(),
+        // In strict mode is this an error, while in relaxed this is just `false`
+        (Value::Nothing { .. }, false) => err(),
+        (Value::String { val, .. }, false) => match strict_string_to_boolean(val, span) {
             Ok(val) => Value::bool(val, span),
             Err(error) => Value::error(error, span),
         },
-        // Propagate errors by explicitly matching them before the final case.
-        Value::Error { .. } => input.clone(),
-        other => Value::error(
-            ShellError::OnlySupportsThisInputType {
-                exp_input_type: "bool, int, float or string".into(),
-                wrong_type: other.get_type().to_string(),
-                dst_span: span,
-                src_span: other.span(),
-            },
-            span,
-        ),
+        _ => match input.coerce_bool() {
+            Ok(val) => Value::bool(val, span),
+            Err(_) => err(),
+        },
     }
 }
 
@@ -165,4 +204,32 @@ mod test {
 
         test_examples(SubCommand {})
     }
+
+    #[test]
+    fn test_strict_handling() {
+        let span = Span::test_data();
+        let args = IntoBoolCmdArgument {
+            cell_paths: vec![].into(),
+            relaxed: false,
+        };
+
+        assert!(action(&Value::test_nothing(), &args, span).is_error());
+        assert!(action(&Value::test_string("abc"), &args, span).is_error());
+        assert!(action(&Value::test_string("true"), &args, span).is_true());
+        assert!(action(&Value::test_string("FALSE"), &args, span).is_false());
+    }
+
+    #[test]
+    fn test_relaxed_handling() {
+        let span = Span::test_data();
+        let args = IntoBoolCmdArgument {
+            cell_paths: vec![].into(),
+            relaxed: true,
+        };
+
+        assert!(action(&Value::test_nothing(), &args, span).is_false());
+        assert!(action(&Value::test_string("abc"), &args, span).is_true());
+        assert!(action(&Value::test_string("true"), &args, span).is_true());
+        assert!(action(&Value::test_string("FALSE"), &args, span).is_false());
+    }
 }

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

@@ -48,7 +48,7 @@ impl UseAnsiColoring {
         let env_value = |env_name| {
             engine_state
                 .get_env_var_insensitive(env_name)
-                .and_then(Value::as_env_bool)
+                .and_then(|v| v.coerce_bool().ok())
                 .unwrap_or(false)
         };
 
@@ -61,7 +61,7 @@ impl UseAnsiColoring {
         }
 
         if let Some(cli_color) = engine_state.get_env_var_insensitive("clicolor") {
-            if let Some(cli_color) = cli_color.as_env_bool() {
+            if let Ok(cli_color) = cli_color.coerce_bool() {
                 return cli_color;
             }
         }

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

@@ -667,7 +667,7 @@ impl Value {
     ///
     /// The following rules are used:
     /// - Values representing `false`:
-    ///   - Empty strings
+    ///   - Empty strings or strings that equal to "false" in any case
     ///   - The number `0` (as an integer, float or string)
     ///   - `Nothing`
     ///   - Explicit boolean `false`
@@ -677,19 +677,19 @@ impl Value {
     ///   - Explicit boolean `true`
     ///
     /// For all other, more complex variants of [`Value`], the function cannot determine a
-    /// boolean representation and returns `None`.
-    pub fn as_env_bool(&self) -> Option<bool> {
+    /// boolean representation and returns `Err`.
+    pub fn coerce_bool(&self) -> Result<bool, ShellError> {
         match self {
-            Value::Bool { val: false, .. }
-            | Value::Int { val: 0, .. }
-            | Value::Float { val: 0.0, .. }
-            | Value::Nothing { .. } => Some(false),
-            Value::String { val, .. } => match val.as_str() {
-                "" | "0" => Some(false),
-                _ => Some(true),
+            Value::Bool { val: false, .. } | Value::Int { val: 0, .. } | Value::Nothing { .. } => {
+                Ok(false)
+            }
+            Value::Float { val, .. } if val <= &f64::EPSILON => Ok(false),
+            Value::String { val, .. } => match val.trim().to_ascii_lowercase().as_str() {
+                "" | "0" | "false" => Ok(false),
+                _ => Ok(true),
             },
-            Value::Bool { .. } | Value::Int { .. } | Value::Float { .. } => Some(true),
-            _ => None,
+            Value::Bool { .. } | Value::Int { .. } | Value::Float { .. } => Ok(true),
+            _ => self.cant_convert_to("bool"),
         }
     }
 
@@ -3916,39 +3916,36 @@ mod tests {
     #[test]
     fn test_env_as_bool() {
         // explicit false values
-        assert_eq!(Value::test_bool(false).as_env_bool(), Some(false));
-        assert_eq!(Value::test_int(0).as_env_bool(), Some(false));
-        assert_eq!(Value::test_float(0.0).as_env_bool(), Some(false));
-        assert_eq!(Value::test_string("").as_env_bool(), Some(false));
-        assert_eq!(Value::test_string("0").as_env_bool(), Some(false));
-        assert_eq!(Value::test_nothing().as_env_bool(), Some(false));
+        assert_eq!(Value::test_bool(false).coerce_bool(), Ok(false));
+        assert_eq!(Value::test_int(0).coerce_bool(), Ok(false));
+        assert_eq!(Value::test_float(0.0).coerce_bool(), Ok(false));
+        assert_eq!(Value::test_string("").coerce_bool(), Ok(false));
+        assert_eq!(Value::test_string("0").coerce_bool(), Ok(false));
+        assert_eq!(Value::test_nothing().coerce_bool(), Ok(false));
 
         // explicit true values
-        assert_eq!(Value::test_bool(true).as_env_bool(), Some(true));
-        assert_eq!(Value::test_int(1).as_env_bool(), Some(true));
-        assert_eq!(Value::test_float(1.0).as_env_bool(), Some(true));
-        assert_eq!(Value::test_string("1").as_env_bool(), Some(true));
+        assert_eq!(Value::test_bool(true).coerce_bool(), Ok(true));
+        assert_eq!(Value::test_int(1).coerce_bool(), Ok(true));
+        assert_eq!(Value::test_float(1.0).coerce_bool(), Ok(true));
+        assert_eq!(Value::test_string("1").coerce_bool(), Ok(true));
 
         // implicit true values
-        assert_eq!(Value::test_int(42).as_env_bool(), Some(true));
-        assert_eq!(Value::test_float(0.5).as_env_bool(), Some(true));
-        assert_eq!(Value::test_string("not zero").as_env_bool(), Some(true));
+        assert_eq!(Value::test_int(42).coerce_bool(), Ok(true));
+        assert_eq!(Value::test_float(0.5).coerce_bool(), Ok(true));
+        assert_eq!(Value::test_string("not zero").coerce_bool(), Ok(true));
 
         // complex values returning None
-        assert_eq!(Value::test_record(Record::default()).as_env_bool(), None);
-        assert_eq!(
-            Value::test_list(vec![Value::test_int(1)]).as_env_bool(),
-            None
-        );
-        assert_eq!(
-            Value::test_date(
-                chrono::DateTime::parse_from_rfc3339("2024-01-01T12:00:00+00:00").unwrap(),
-            )
-            .as_env_bool(),
-            None
-        );
-        assert_eq!(Value::test_glob("*.rs").as_env_bool(), None);
-        assert_eq!(Value::test_binary(vec![1, 2, 3]).as_env_bool(), None);
-        assert_eq!(Value::test_duration(3600).as_env_bool(), None);
+        assert!(Value::test_record(Record::default()).coerce_bool().is_err());
+        assert!(Value::test_list(vec![Value::test_int(1)])
+            .coerce_bool()
+            .is_err());
+        assert!(Value::test_date(
+            chrono::DateTime::parse_from_rfc3339("2024-01-01T12:00:00+00:00").unwrap(),
+        )
+        .coerce_bool()
+        .is_err());
+        assert!(Value::test_glob("*.rs").coerce_bool().is_err());
+        assert!(Value::test_binary(vec![1, 2, 3]).coerce_bool().is_err());
+        assert!(Value::test_duration(3600).coerce_bool().is_err());
     }
 }