Add uniq command (#1132)

* start playing with ways to use the uniq command

* WIP

* Got uniq working, but still need to figure out args issue and add tests

* Add some tests for uniq

* fmt

* remove commented out code

* Add documentation and some additional tests showing uniq values and rows. Also removed args TODO

* add changes that didn't get committed

* whoops, I didn't save the docs correctly...

* fmt

* Add a test for uniq with nested json

* Add another test

* Fix unique-ness when json keys are out of order and make the test json more complicated

tests/commands/uniq.rs

@@ -0,0 +1,118 @@
+use nu_test_support::fs::Stub::FileWithContentToBeTrimmed;
+use nu_test_support::playground::Playground;
+use nu_test_support::{nu, pipeline};
+
+#[test]
+fn uniq_rows() {
+    Playground::setup("uniq_test_1", |dirs, sandbox| {
+        sandbox.with_files(vec![FileWithContentToBeTrimmed(
+            "los_tres_caballeros.csv",
+            r#"
+                first_name,last_name,rusty_at,type
+                Andrés,Robalino,10/11/2013,A
+                Jonathan,Turner,10/12/2013,B
+                Yehuda,Katz,10/11/2013,A
+                Jonathan,Turner,10/12/2013,B
+                Yehuda,Katz,10/11/2013,A
+            "#,
+        )]);
+
+        let actual = nu!(
+            cwd: dirs.test(), pipeline(
+            r#"
+                open los_tres_caballeros.csv
+                | uniq
+                | count
+                | echo $it
+            "#
+        ));
+
+        assert_eq!(actual, "3");
+    })
+}
+
+#[test]
+fn uniq_columns() {
+    Playground::setup("uniq_test_2", |dirs, sandbox| {
+        sandbox.with_files(vec![FileWithContentToBeTrimmed(
+            "los_tres_caballeros.csv",
+            r#"
+                first_name,last_name,rusty_at,type
+                Andrés,Robalino,10/11/2013,A
+                Jonathan,Turner,10/12/2013,B
+                Yehuda,Katz,10/11/2013,A
+                Jonathan,Turner,10/12/2013,B
+                Yehuda,Katz,10/11/2013,A
+            "#,
+        )]);
+
+        let actual = nu!(
+            cwd: dirs.test(), pipeline(
+            r#"
+                open los_tres_caballeros.csv
+                | pick rusty_at type
+                | uniq
+                | count
+                | echo $it
+            "#
+        ));
+
+        assert_eq!(actual, "2");
+    })
+}
+
+#[test]
+fn uniq_values() {
+    Playground::setup("uniq_test_3", |dirs, sandbox| {
+        sandbox.with_files(vec![FileWithContentToBeTrimmed(
+            "los_tres_caballeros.csv",
+            r#"
+                first_name,last_name,rusty_at,type
+                Andrés,Robalino,10/11/2013,A
+                Jonathan,Turner,10/12/2013,B
+                Yehuda,Katz,10/11/2013,A
+                Jonathan,Turner,10/12/2013,B
+                Yehuda,Katz,10/11/2013,A
+            "#,
+        )]);
+
+        let actual = nu!(
+            cwd: dirs.test(), pipeline(
+            r#"
+                open los_tres_caballeros.csv
+                | pick get type
+                | uniq
+                | count
+                | echo $it
+            "#
+        ));
+
+        assert_eq!(actual, "2");
+    })
+}
+
+#[test]
+fn uniq_when_keys_out_of_order() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats", pipeline(
+        r#"
+            echo '[{"a": "a", "b": [1,2,3]},{"b": [1,2,3], "a": "a"}]'
+            | from-json
+            | uniq
+            | count
+            | echo $it
+        "#
+    ));
+
+    assert_eq!(actual, "1");
+}
+
+#[test]
+fn uniq_nested_json_structures() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats",
+        "open nested_uniq.json | uniq | count | echo $it"
+    );
+
+    assert_eq!(actual, "3");
+}