Bring back parse as built-in.

crates/nu-cli/src/cli.rs

@@ -291,6 +291,7 @@ pub fn create_default_context(
             whole_stream_command(Lines),
             whole_stream_command(Trim),
             whole_stream_command(Echo),
+            whole_stream_command(Parse),
             whole_stream_command(Str),
             whole_stream_command(StrToDecimal),
             whole_stream_command(StrToInteger),

crates/nu-cli/src/commands.rs

@@ -74,6 +74,7 @@ pub(crate) mod mv;
 pub(crate) mod next;
 pub(crate) mod nth;
 pub(crate) mod open;
+pub(crate) mod parse;
 pub(crate) mod pivot;
 pub(crate) mod plugin;
 pub(crate) mod prepend;
@@ -203,6 +204,7 @@ pub(crate) use mv::Move;
 pub(crate) use next::Next;
 pub(crate) use nth::Nth;
 pub(crate) use open::Open;
+pub(crate) use parse::Parse;
 pub(crate) use pivot::Pivot;
 pub(crate) use prepend::Prepend;
 pub(crate) use prev::Previous;

crates/nu-cli/src/commands/parse/command.rs

@@ -0,0 +1,175 @@
+use crate::commands::WholeStreamCommand;
+use crate::prelude::*;
+use nu_errors::ShellError;
+use nu_protocol::{Signature, SyntaxShape, TaggedDictBuilder, UntaggedValue, Value};
+use nu_source::Tagged;
+
+use regex::Regex;
+
+#[derive(Deserialize)]
+struct Arguments {
+    pattern: Tagged<String>,
+    regex: Tagged<bool>,
+}
+
+pub struct Command;
+
+#[async_trait]
+impl WholeStreamCommand for Command {
+    fn name(&self) -> &str {
+        "parse"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("parse")
+            .required(
+                "pattern",
+                SyntaxShape::String,
+                "the pattern to match. Eg) \"{foo}: {bar}\"",
+            )
+            .switch("regex", "use full regex syntax for patterns", Some('r'))
+    }
+
+    fn usage(&self) -> &str {
+        "Parse columns from string data using a simple pattern."
+    }
+
+    async fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        operate(args, registry).await
+    }
+}
+
+pub async fn operate(
+    args: CommandArgs,
+    registry: &CommandRegistry,
+) -> Result<OutputStream, ShellError> {
+    let name_tag = args.call_info.name_tag.clone();
+    let (Arguments { regex, pattern }, mut input) = args.process(&registry).await?;
+
+    let regex_pattern = if let Tagged { item: true, tag } = regex {
+        Regex::new(&pattern.item)
+            .map_err(|_| ShellError::labeled_error("Invalid regex", "invalid regex", tag.span))?
+    } else {
+        let parse_regex = build_regex(&pattern.item, name_tag.clone())?;
+
+        Regex::new(&parse_regex).map_err(|_| {
+            ShellError::labeled_error("Invalid pattern", "invalid pattern", name_tag.span)
+        })?
+    };
+
+    let columns = column_names(&regex_pattern);
+    let mut parsed: VecDeque<Value> = VecDeque::new();
+
+    while let Some(v) = input.next().await {
+        match v.as_string() {
+            Ok(s) => {
+                let results = regex_pattern.captures_iter(&s);
+
+                for c in results {
+                    let mut dict = TaggedDictBuilder::new(&v.tag);
+
+                    for (column_name, cap) in columns.iter().zip(c.iter().skip(1)) {
+                        let cap_string = cap.map(|v| v.as_str()).unwrap_or("").to_string();
+                        dict.insert_untagged(column_name, UntaggedValue::string(cap_string));
+                    }
+
+                    parsed.push_back(dict.into_value());
+                }
+            }
+            Err(_) => {
+                return Err(ShellError::labeled_error_with_secondary(
+                    "Expected string input",
+                    "expected string input",
+                    &name_tag,
+                    "value originated here",
+                    v.tag,
+                ))
+            }
+        }
+    }
+
+    Ok(futures::stream::iter(parsed).to_output_stream())
+}
+
+fn build_regex(input: &str, tag: Tag) -> Result<String, ShellError> {
+    let mut output = "(?s)\\A".to_string();
+
+    //let mut loop_input = input;
+    let mut loop_input = input.chars().peekable();
+    loop {
+        let mut before = String::new();
+        while let Some(c) = loop_input.next() {
+            if c == '{' {
+                // If '{{', still creating a plaintext parse command, but just for a single '{' char
+                if loop_input.peek() == Some(&'{') {
+                    let _ = loop_input.next();
+                } else {
+                    break;
+                }
+            }
+            before.push(c);
+        }
+
+        if !before.is_empty() {
+            output.push_str(&regex::escape(&before));
+        }
+
+        // Look for column as we're now at one
+        let mut column = String::new();
+        while let Some(c) = loop_input.next() {
+            if c == '}' {
+                break;
+            }
+            column.push(c);
+
+            if loop_input.peek().is_none() {
+                return Err(ShellError::labeled_error(
+                    "Found opening `{` without an associated closing `}`",
+                    "invalid parse pattern",
+                    tag,
+                ));
+            }
+        }
+
+        if !column.is_empty() {
+            output.push_str("(?P<");
+            output.push_str(&column);
+            output.push_str(">.*?)");
+        }
+
+        if before.is_empty() && column.is_empty() {
+            break;
+        }
+    }
+
+    output.push_str("\\z");
+    Ok(output)
+}
+
+fn column_names(regex: &Regex) -> Vec<String> {
+    regex
+        .capture_names()
+        .enumerate()
+        .skip(1)
+        .map(|(i, name)| {
+            name.map(String::from)
+                .unwrap_or_else(|| format!("Capture{}", i))
+        })
+        .collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Command;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Command {})
+    }
+}

crates/nu-cli/src/commands/parse/mod.rs

@@ -0,0 +1,3 @@
+mod command;
+
+pub use command::Command as Parse;