Uniq: --count flag to count occurences (#2017)

* uniq: Add counting option (WIP!)

Usage:

fetch https://raw.githubusercontent.com/timbray/topfew/master/test/data/access-1k | lines | wrap item | uniq | sort-by count | last 10

* uniq: Add first test

* uniq: Re-enable the non-counting variant.

* uniq: Also handle primitive lines.

* uniq: Update documentation

* uniq: Final comment about error handling. Let's get some feedback

* uniq: Address review comments.

Not happy with the way I create a TypeError. There must be a cleaner
way. Anyway, good for shipping.

* uniq: Use Labeled_error as suggested by jturner in chat.

* uniq: Return error directly.

Co-authored-by: Christoph Siedentop <christoph@siedentop.name>

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

@@ -1,9 +1,9 @@
 use crate::commands::WholeStreamCommand;
 use crate::context::CommandRegistry;
 use crate::prelude::*;
-use indexmap::set::IndexSet;
+use indexmap::map::IndexMap;
 use nu_errors::ShellError;
-use nu_protocol::{ReturnSuccess, Signature};
+use nu_protocol::Signature;
 
 pub struct Uniq;
 
@@ -14,7 +14,7 @@ impl WholeStreamCommand for Uniq {
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("uniq")
+        Signature::build("uniq").switch("count", "Count the unique rows", Some('c'))
     }
 
     fn usage(&self) -> &str {
@@ -30,17 +30,66 @@ impl WholeStreamCommand for Uniq {
     }
 }
 
-async fn uniq(args: CommandArgs, _registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+async fn uniq(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
+    let args = args.evaluate_once(&registry).await?;
+    let should_show_count = args.has("count");
     let input = args.input;
-    let uniq_values: IndexSet<_> = input.collect().await;
+    let uniq_values = {
+        let mut counter = IndexMap::<nu_protocol::Value, usize>::new();
+        for line in input.into_vec().await {
+            *counter.entry(line).or_insert(0) += 1;
+        }
+        counter
+    };
 
     let mut values_vec_deque = VecDeque::new();
 
-    for item in uniq_values
-        .iter()
-        .map(|row| ReturnSuccess::value(row.clone()))
-    {
-        values_vec_deque.push_back(item);
+    if should_show_count {
+        for item in uniq_values {
+            use nu_protocol::{UntaggedValue, Value};
+            let value = {
+                match item.0.value {
+                    UntaggedValue::Row(mut row) => {
+                        row.entries.insert(
+                            "count".to_string(),
+                            UntaggedValue::int(item.1).into_untagged_value(),
+                        );
+                        Value {
+                            value: UntaggedValue::Row(row),
+                            tag: item.0.tag,
+                        }
+                    }
+                    UntaggedValue::Primitive(p) => {
+                        let mut map = IndexMap::<String, Value>::new();
+                        map.insert(
+                            "value".to_string(),
+                            UntaggedValue::Primitive(p).into_untagged_value(),
+                        );
+                        map.insert(
+                            "count".to_string(),
+                            UntaggedValue::int(item.1).into_untagged_value(),
+                        );
+                        Value {
+                            value: UntaggedValue::row(map),
+                            tag: item.0.tag,
+                        }
+                    }
+                    UntaggedValue::Table(_) => {
+                        return Err(ShellError::labeled_error(
+                            "uniq -c cannot operate on tables.",
+                            "source",
+                            item.0.tag.span,
+                        ))
+                    }
+                    UntaggedValue::Error(_) | UntaggedValue::Block(_) => item.0,
+                }
+            };
+            values_vec_deque.push_back(value);
+        }
+    } else {
+        for item in uniq_values {
+            values_vec_deque.push_back(item.0);
+        }
     }
 
     Ok(futures::stream::iter(values_vec_deque).to_output_stream())

crates/nu-cli/tests/commands/uniq.rs

@@ -140,3 +140,26 @@ fn uniq_when_keys_out_of_order() {
 
     assert_eq!(actual.out, "1");
 }
+
+#[test]
+fn uniq_counting() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats", pipeline(
+        r#"
+            echo '["A", "B", "A"]'
+            | from json
+            | wrap item
+            | uniq --count
+        "#
+    ));
+    let expected = nu!(
+        cwd: "tests/fixtures/formats", pipeline(
+        r#"
+        echo '[{"item": "A", "count": 2}, {"item": "B", "count": 1}]'
+        | from json
+        "#
+    ));
+    print!("{}", actual.out);
+    print!("{}", expected.out);
+    assert_eq!(actual.out, expected.out);
+}

docs/commands/uniq.md

@@ -34,3 +34,16 @@ Yehuda,Katz,10/11/2013,A
  1 │ B
 ━━━┷━━━━━━━━━
 ```
+
+### Counting
+`--count` or `-c` is the flag to output a `count` column.
+
+```
+> `open test.csv | get type | uniq -c`
+───┬───────┬───────
+ # │ value │ count 
+───┼───────┼───────
+ 0 │ A     │     3 
+ 1 │ B     │     2 
+───┴───────┴───────
+```