Move most of the root package into a subcrate. (#1445)

This improves incremental build time when working on what was previously
the root package. For example, previously all plugins would be rebuilt
with a change to `src/commands/classified/external.rs`, but now only
`nu-cli` will have to be rebuilt (and anything that depends on it).

crates/nu-cli/src/commands/from_json.rs

@@ -0,0 +1,159 @@
+use crate::commands::WholeStreamCommand;
+use crate::prelude::*;
+use nu_errors::ShellError;
+use nu_protocol::{Primitive, ReturnSuccess, Signature, TaggedDictBuilder, UntaggedValue, Value};
+
+pub struct FromJSON;
+
+#[derive(Deserialize)]
+pub struct FromJSONArgs {
+    objects: bool,
+}
+
+impl WholeStreamCommand for FromJSON {
+    fn name(&self) -> &str {
+        "from-json"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("from-json").switch(
+            "objects",
+            "treat each line as a separate value",
+            Some('o'),
+        )
+    }
+
+    fn usage(&self) -> &str {
+        "Parse text as .json and create table."
+    }
+
+    fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        args.process(registry, from_json)?.run()
+    }
+}
+
+fn convert_json_value_to_nu_value(v: &serde_hjson::Value, tag: impl Into<Tag>) -> Value {
+    let tag = tag.into();
+
+    match v {
+        serde_hjson::Value::Null => UntaggedValue::Primitive(Primitive::Nothing).into_value(&tag),
+        serde_hjson::Value::Bool(b) => UntaggedValue::boolean(*b).into_value(&tag),
+        serde_hjson::Value::F64(n) => UntaggedValue::decimal(*n).into_value(&tag),
+        serde_hjson::Value::U64(n) => UntaggedValue::int(*n).into_value(&tag),
+        serde_hjson::Value::I64(n) => UntaggedValue::int(*n).into_value(&tag),
+        serde_hjson::Value::String(s) => {
+            UntaggedValue::Primitive(Primitive::String(String::from(s))).into_value(&tag)
+        }
+        serde_hjson::Value::Array(a) => UntaggedValue::Table(
+            a.iter()
+                .map(|x| convert_json_value_to_nu_value(x, &tag))
+                .collect(),
+        )
+        .into_value(tag),
+        serde_hjson::Value::Object(o) => {
+            let mut collected = TaggedDictBuilder::new(&tag);
+            for (k, v) in o.iter() {
+                collected.insert_value(k.clone(), convert_json_value_to_nu_value(v, &tag));
+            }
+
+            collected.into_value()
+        }
+    }
+}
+
+pub fn from_json_string_to_value(s: String, tag: impl Into<Tag>) -> serde_hjson::Result<Value> {
+    let v: serde_hjson::Value = serde_hjson::from_str(&s)?;
+    Ok(convert_json_value_to_nu_value(&v, tag))
+}
+
+fn from_json(
+    FromJSONArgs { objects }: FromJSONArgs,
+    RunnableContext { input, name, .. }: RunnableContext,
+) -> Result<OutputStream, ShellError> {
+    let name_span = name.span;
+    let name_tag = name;
+
+    let stream = async_stream! {
+        let values: Vec<Value> = input.values.collect().await;
+
+        let mut concat_string = String::new();
+        let mut latest_tag: Option<Tag> = None;
+
+        for value in values {
+            latest_tag = Some(value.tag.clone());
+            let value_span = value.tag.span;
+
+            if let Ok(s) = value.as_string() {
+                concat_string.push_str(&s);
+            } else {
+                yield Err(ShellError::labeled_error_with_secondary(
+                    "Expected a string from pipeline",
+                    "requires string input",
+                    name_span,
+                    "value originates from here",
+                    value_span,
+                ))
+            }
+        }
+
+
+        if objects {
+            for json_str in concat_string.lines() {
+                if json_str.is_empty() {
+                    continue;
+                }
+
+                match from_json_string_to_value(json_str.to_string(), &name_tag) {
+                    Ok(x) =>
+                        yield ReturnSuccess::value(x),
+                    Err(e) => {
+                        if let Some(ref last_tag) = latest_tag {
+                            let mut message = "Could not parse as JSON (".to_string();
+                            message.push_str(&e.to_string());
+                            message.push_str(")");
+
+                            yield Err(ShellError::labeled_error_with_secondary(
+                                message,
+                                "input cannot be parsed as JSON",
+                                &name_tag,
+                                "value originates from here",
+                                last_tag))
+                        }
+                    }
+                }
+            }
+        } else {
+            match from_json_string_to_value(concat_string, name_tag.clone()) {
+                Ok(x) =>
+                    match x {
+                        Value { value: UntaggedValue::Table(list), .. } => {
+                            for l in list {
+                                yield ReturnSuccess::value(l);
+                            }
+                        }
+                        x => yield ReturnSuccess::value(x),
+                    }
+                Err(e) => {
+                    if let Some(last_tag) = latest_tag {
+                        let mut message = "Could not parse as JSON (".to_string();
+                        message.push_str(&e.to_string());
+                        message.push_str(")");
+
+                        yield Err(ShellError::labeled_error_with_secondary(
+                            message,
+                            "input cannot be parsed as JSON",
+                            name_tag,
+                            "value originates from here",
+                            last_tag))
+                    }
+                }
+            }
+        }
+    };
+
+    Ok(stream.to_output_stream())
+}