Add url decode command (nushell#10611)

Implemented URL decoding as a url subcommand, created corresponding unit
tests. The logic, examples and descriptions were based on the existing
`url encode` command.

Resolves nushell#10563

# Description
Added a new `url decode` command to compliment the existing `url
encode`, as proposed by myself in nushell#10563.
It takes a string, list of strings or cell path and produces the
corresponding decoded strings.

![image](https://github.com/nushell/nushell/assets/4030336/815a34e9-7ceb-4d09-9d74-e700ba513b17)

# User-Facing Changes
New url subcommand `url decode`, as described above.

# Tests + Formatting
I've added unit tests for the new subcommand and ensured all actions
outlined below showed no issues.
- [x] `cargo fmt --all -- --check`
- [x] `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used`
- [x] `cargo test --workspace`
- [x] `cargo run -- -c "use std testing; testing run-tests --path
crates/nu-std"`

crates/nu-command/src/default_context.rs

@@ -357,6 +357,7 @@ pub fn add_shell_command_context(mut engine_state: EngineState) -> EngineState {
             HttpOptions,
             Url,
             UrlBuildQuery,
+            UrlDecode,
             UrlEncode,
             UrlJoin,
             UrlParse,

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

@@ -0,0 +1,122 @@
+use nu_cmd_base::input_handler::{operate, CellPathOnlyArgs};
+use nu_engine::CallExt;
+use nu_protocol::ast::{Call, CellPath};
+use nu_protocol::engine::{Command, EngineState, Stack};
+use nu_protocol::Category;
+use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value};
+use percent_encoding::percent_decode_str;
+
+#[derive(Clone)]
+pub struct SubCommand;
+
+impl Command for SubCommand {
+    fn name(&self) -> &str {
+        "url decode"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("url decode")
+            .input_output_types(vec![
+                (Type::String, Type::String),
+                (
+                    Type::List(Box::new(Type::String)),
+                    Type::List(Box::new(Type::String)),
+                ),
+                (Type::Table(vec![]), Type::Table(vec![])),
+                (Type::Record(vec![]), Type::Record(vec![])),
+            ])
+            .allow_variants_without_examples(true)
+            .rest(
+                "rest",
+                SyntaxShape::CellPath,
+                "For a data structure input, url decode strings at the given cell paths",
+            )
+            .category(Category::Strings)
+    }
+
+    fn usage(&self) -> &str {
+        "Converts a percent-encoded web safe string to a string."
+    }
+
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["string", "text", "convert"]
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        let cell_paths: Vec<CellPath> = call.rest(engine_state, stack, 0)?;
+        let args = CellPathOnlyArgs::from(cell_paths);
+        operate(action, args, input, call.head, engine_state.ctrlc.clone())
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Decode a url with escape characters",
+                example: "'https://example.com/foo%20bar' | url decode",
+                result: Some(Value::test_string("https://example.com/foo bar")),
+            },
+            Example {
+                description: "Decode multiple urls with escape characters in list",
+                example: "['https://example.com/foo%20bar' 'https://example.com/a%3Eb' '%E4%B8%AD%E6%96%87%E5%AD%97/eng/12%2034'] | url decode",
+                result: Some(Value::list(
+                    vec![
+                        Value::test_string("https://example.com/foo bar"),
+                        Value::test_string("https://example.com/a>b"),
+                        Value::test_string("中文字/eng/12 34"),
+                    ],
+                    Span::test_data(),
+                )),
+            },
+        ]
+    }
+}
+
+fn action(input: &Value, _arg: &CellPathOnlyArgs, head: Span) -> Value {
+    let input_span = input.span();
+    match input {
+        Value::String { val, .. } => {
+            let val = percent_decode_str(val).decode_utf8();
+            match val {
+                Ok(val) => Value::string(val, head),
+                Err(e) => Value::error(
+                    ShellError::GenericError(
+                        "Failed to decode string".into(),
+                        e.to_string(),
+                        Some(input_span),
+                        None,
+                        Vec::new(),
+                    ),
+                    head,
+                ),
+            }
+        }
+        Value::Error { .. } => input.clone(),
+        _ => Value::error(
+            ShellError::OnlySupportsThisInputType {
+                exp_input_type: "string".into(),
+                wrong_type: input.get_type().to_string(),
+                dst_span: head,
+                src_span: input.span(),
+            },
+            head,
+        ),
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_examples() {
+        use crate::test_examples;
+
+        test_examples(SubCommand {})
+    }
+}

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

@@ -1,4 +1,5 @@
 mod build_query;
+mod decode;
 mod encode;
 mod join;
 mod parse;
@@ -8,6 +9,7 @@ use url::{self};
 
 pub use self::parse::SubCommand as UrlParse;
 pub use build_query::SubCommand as UrlBuildQuery;
+pub use decode::SubCommand as UrlDecode;
 pub use encode::SubCommand as UrlEncode;
 pub use join::SubCommand as UrlJoin;
 pub use url_::Url;

crates/nu-command/tests/commands/url/decode.rs

@@ -0,0 +1,19 @@
+use nu_test_support::nu;
+
+#[test]
+fn url_decode_simple() {
+    let actual = nu!(r#"'a%20b' | url decode"#);
+    assert_eq!(actual.out, "a b");
+}
+
+#[test]
+fn url_decode_special_characters() {
+    let actual = nu!(r#"'%21%40%23%24%25%C2%A8%26%2A%2D%2B%3B%2C%7B%7D%5B%5D%28%29' | url decode"#);
+    assert_eq!(actual.out, r#"!@#$%¨&*-+;,{}[]()"#);
+}
+
+#[test]
+fn url_decode_error_invalid_utf8() {
+    let actual = nu!(r#"'%99' | url decode"#);
+    assert!(actual.err.contains("invalid utf-8 sequence"));
+}

crates/nu-command/tests/commands/url/mod.rs

@@ -1,2 +1,3 @@
+mod decode;
 mod join;
 mod parse;