Create Record type (#10103)

# Description
This PR creates a new `Record` type to reduce duplicate code and
possibly bugs as well. (This is an edited version of #9648.)
- `Record` implements `FromIterator` and `IntoIterator` and so can be
iterated over or collected into. For example, this helps with
conversions to and from (hash)maps. (Also, no more
`cols.iter().zip(vals)`!)
- `Record` has a `push(col, val)` function to help insure that the
number of columns is equal to the number of values. I caught a few
potential bugs thanks to this (e.g. in the `ls` command).
- Finally, this PR also adds a `record!` macro that helps simplify
record creation. It is used like so:
   ```rust
   record! {
       "key1" => some_value,
       "key2" => Value::string("text", span),
       "key3" => Value::int(optional_int.unwrap_or(0), span),
       "key4" => Value::bool(config.setting, span),
   }
   ```
Since macros hinder formatting, etc., the right hand side values should
be relatively short and sweet like the examples above.

Where possible, prefer `record!` or `.collect()` on an iterator instead
of multiple `Record::push`s, since the first two automatically set the
record capacity and do less work overall.

# User-Facing Changes
Besides the changes in `nu-protocol` the only other breaking changes are
to `nu-table::{ExpandedTable::build_map, JustTable::kv_table}`.

crates/nu-command/src/math/max.rs

@@ -2,7 +2,9 @@ use crate::math::reducers::{reducer_for, Reduce};
 use crate::math::utils::run_with_function;
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
-use nu_protocol::{Category, Example, PipelineData, ShellError, Signature, Span, Type, Value};
+use nu_protocol::{
+    Category, Example, PipelineData, Record, ShellError, Signature, Span, Type, Value,
+};
 
 #[derive(Clone)]
 pub struct SubCommand;
@@ -50,11 +52,10 @@ impl Command for SubCommand {
             Example {
                 description: "Find the maxima of the columns of a table",
                 example: "[{a: 1 b: 3} {a: 2 b: -1}] | math max",
-                result: Some(Value::Record {
+                result: Some(Value::test_record(Record {
                     cols: vec!["a".to_string(), "b".to_string()],
                     vals: vec![Value::test_int(2), Value::test_int(3)],
-                    span: Span::test_data(),
-                }),
+                })),
             },
         ]
     }

crates/nu-command/src/math/median.rs

@@ -4,7 +4,9 @@ use crate::math::avg::average;
 use crate::math::utils::run_with_function;
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
-use nu_protocol::{Category, Example, PipelineData, ShellError, Signature, Span, Type, Value};
+use nu_protocol::{
+    Category, Example, PipelineData, Record, ShellError, Signature, Span, Type, Value,
+};
 
 #[derive(Clone)]
 pub struct SubCommand;
@@ -54,11 +56,10 @@ impl Command for SubCommand {
             Example {
                 description: "Compute the medians of the columns of a table",
                 example: "[{a: 1 b: 3} {a: 2 b: -1} {a: -3 b: 5}] | math median",
-                result: Some(Value::Record {
+                result: Some(Value::test_record(Record {
                     cols: vec!["a".to_string(), "b".to_string()],
                     vals: vec![Value::test_int(1), Value::test_int(3)],
-                    span: Span::test_data(),
-                }),
+                })),
             },
         ]
     }

crates/nu-command/src/math/min.rs

@@ -2,7 +2,9 @@ use crate::math::reducers::{reducer_for, Reduce};
 use crate::math::utils::run_with_function;
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
-use nu_protocol::{Category, Example, PipelineData, ShellError, Signature, Span, Type, Value};
+use nu_protocol::{
+    Category, Example, PipelineData, Record, ShellError, Signature, Span, Type, Value,
+};
 
 #[derive(Clone)]
 pub struct SubCommand;
@@ -50,11 +52,10 @@ impl Command for SubCommand {
             Example {
                 description: "Compute the minima of the columns of a table",
                 example: "[{a: 1 b: 3} {a: 2 b: -1}] | math min",
-                result: Some(Value::Record {
+                result: Some(Value::test_record(Record {
                     cols: vec!["a".to_string(), "b".to_string()],
                     vals: vec![Value::test_int(1), Value::test_int(-1)],
-                    span: Span::test_data(),
-                }),
+                })),
             },
             Example {
                 description: "Find the minimum of a list of arbitrary values (Warning: Weird)",

crates/nu-command/src/math/mode.rs

@@ -1,7 +1,9 @@
 use crate::math::utils::run_with_function;
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
-use nu_protocol::{Category, Example, PipelineData, ShellError, Signature, Span, Type, Value};
+use nu_protocol::{
+    Category, Example, PipelineData, Record, ShellError, Signature, Span, Type, Value,
+};
 use std::cmp::Ordering;
 use std::collections::HashMap;
 
@@ -88,7 +90,7 @@ impl Command for SubCommand {
             Example {
                 description: "Compute the mode(s) of the columns of a table",
                 example: "[{a: 1 b: 3} {a: 2 b: -1} {a: 1 b: 5}] | math mode",
-                result: Some(Value::Record {
+                result: Some(Value::test_record(Record {
                     cols: vec!["a".to_string(), "b".to_string()],
                     vals: vec![
                         Value::List {
@@ -100,8 +102,7 @@ impl Command for SubCommand {
                             span: Span::test_data(),
                         },
                     ],
-                    span: Span::test_data(),
-                }),
+                })),
             },
         ]
     }

crates/nu-command/src/math/utils.rs

@@ -1,6 +1,6 @@
 use indexmap::map::IndexMap;
 use nu_protocol::ast::Call;
-use nu_protocol::{IntoPipelineData, PipelineData, ShellError, Span, Spanned, Value};
+use nu_protocol::{IntoPipelineData, PipelineData, Record, ShellError, Span, Value};
 
 pub fn run_with_function(
     call: &Call,
@@ -26,8 +26,8 @@ fn helper_for_tables(
     let mut column_values = IndexMap::new();
     for val in values {
         match val {
-            Value::Record { cols, vals, .. } => {
-                for (key, value) in cols.iter().zip(vals.iter()) {
+            Value::Record { val, .. } => {
+                for (key, value) in val {
                     column_values
                         .entry(key.clone())
                         .and_modify(|v: &mut Vec<Value>| v.push(value.clone()))
@@ -57,10 +57,7 @@ fn helper_for_tables(
         ));
     }
 
-    Ok(Value::from(Spanned {
-        item: column_totals,
-        span: name,
-    }))
+    Ok(Value::record(column_totals.into_iter().collect(), name))
 }
 
 pub fn calculate(
@@ -83,15 +80,20 @@ pub fn calculate(
             ),
             _ => mf(vals, span, name),
         },
-        PipelineData::Value(Value::Record { vals, cols, span }, ..) => {
-            let new_vals: Result<Vec<Value>, ShellError> =
-                vals.into_iter().map(|val| mf(&[val], span, name)).collect();
+        PipelineData::Value(Value::Record { val: record, span }, ..) => {
+            let new_vals: Result<Vec<Value>, ShellError> = record
+                .vals
+                .into_iter()
+                .map(|val| mf(&[val], span, name))
+                .collect();
             match new_vals {
-                Ok(vec) => Ok(Value::Record {
-                    cols,
-                    vals: vec,
+                Ok(vec) => Ok(Value::record(
+                    Record {
+                        cols: record.cols,
+                        vals: vec,
+                    },
                     span,
-                }),
+                )),
                 Err(err) => Err(err),
             }
         }