Rows and values can be checked for emptiness. Allows to set a value if desired. (#1665)

crates/nu-cli/src/cli.rs

@@ -307,6 +307,7 @@ pub fn create_default_context(
             whole_stream_command(Rename),
             whole_stream_command(Uniq),
             per_item_command(Each),
+            per_item_command(IsEmpty),
             // Table manipulation
             whole_stream_command(Shuffle),
             whole_stream_command(Wrap),

crates/nu-cli/src/commands.rs

@@ -54,6 +54,7 @@ pub(crate) mod help;
 pub(crate) mod histogram;
 pub(crate) mod history;
 pub(crate) mod insert;
+pub(crate) mod is_empty;
 pub(crate) mod last;
 pub(crate) mod lines;
 pub(crate) mod ls;
@@ -135,6 +136,7 @@ pub(crate) use du::Du;
 pub(crate) use each::Each;
 pub(crate) use echo::Echo;
 pub(crate) use edit::Edit;
+pub(crate) use is_empty::IsEmpty;
 pub(crate) mod kill;
 pub(crate) use kill::Kill;
 pub(crate) mod clear;

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

@@ -0,0 +1,203 @@
+use crate::commands::PerItemCommand;
+use crate::context::CommandRegistry;
+use crate::prelude::*;
+use nu_errors::ShellError;
+use nu_protocol::{
+    CallInfo, ColumnPath, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value,
+};
+use nu_source::Tagged;
+use nu_value_ext::ValueExt;
+
+enum IsEmptyFor {
+    Value,
+    RowWithFieldsAndFallback(Vec<Tagged<ColumnPath>>, Value),
+    RowWithField(Tagged<ColumnPath>),
+    RowWithFieldAndFallback(Box<Tagged<ColumnPath>>, Value),
+}
+
+pub struct IsEmpty;
+
+impl PerItemCommand for IsEmpty {
+    fn name(&self) -> &str {
+        "empty?"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("empty?").rest(
+            SyntaxShape::Any,
+            "the names of the columns to check emptiness followed by the replacement value.",
+        )
+    }
+
+    fn usage(&self) -> &str {
+        "Checks emptiness. The last value is the replacement value for any empty column(s) given to check against the table."
+    }
+
+    fn run(
+        &self,
+        call_info: &CallInfo,
+        _registry: &CommandRegistry,
+        _raw_args: &RawCommandArgs,
+        value: Value,
+    ) -> Result<OutputStream, ShellError> {
+        let value_tag = value.tag();
+
+        let action = if call_info.args.len() <= 2 {
+            let field = call_info.args.expect_nth(0);
+            let replacement_if_true = call_info.args.expect_nth(1);
+
+            match (field, replacement_if_true) {
+                (Ok(field), Ok(replacement_if_true)) => IsEmptyFor::RowWithFieldAndFallback(
+                    Box::new(field.as_column_path()?),
+                    replacement_if_true.clone(),
+                ),
+                (Ok(field), Err(_)) => IsEmptyFor::RowWithField(field.as_column_path()?),
+                (_, _) => IsEmptyFor::Value,
+            }
+        } else {
+            let no_args = vec![];
+            let mut arguments = call_info
+                .args
+                .positional
+                .as_ref()
+                .unwrap_or_else(|| &no_args)
+                .iter()
+                .rev();
+            let replacement_if_true = match arguments.next() {
+                Some(arg) => arg.clone(),
+                None => UntaggedValue::boolean(value.is_empty()).into_value(&value_tag),
+            };
+
+            IsEmptyFor::RowWithFieldsAndFallback(
+                arguments
+                    .map(|a| a.as_column_path())
+                    .filter_map(Result::ok)
+                    .collect(),
+                replacement_if_true,
+            )
+        };
+
+        match action {
+            IsEmptyFor::Value => Ok(futures::stream::iter(vec![Ok(ReturnSuccess::Value(
+                UntaggedValue::boolean(value.is_empty()).into_value(value_tag),
+            ))])
+            .to_output_stream()),
+            IsEmptyFor::RowWithFieldsAndFallback(fields, default) => {
+                let mut out = value;
+
+                for field in fields.iter() {
+                    let val =
+                        out.get_data_by_column_path(&field, Box::new(move |(_, _, err)| err))?;
+
+                    let emptiness_value = match out {
+                        obj
+                        @
+                        Value {
+                            value: UntaggedValue::Row(_),
+                            ..
+                        } => {
+                            if val.is_empty() {
+                                match obj.replace_data_at_column_path(&field, default.clone()) {
+                                    Some(v) => Ok(v),
+                                    None => Err(ShellError::labeled_error(
+                                        "empty? could not find place to check emptiness",
+                                        "column name",
+                                        &field.tag,
+                                    )),
+                                }
+                            } else {
+                                Ok(obj)
+                            }
+                        }
+                        _ => Err(ShellError::labeled_error(
+                            "Unrecognized type in stream",
+                            "original value",
+                            &value_tag,
+                        )),
+                    };
+
+                    out = emptiness_value?;
+                }
+
+                Ok(futures::stream::iter(vec![Ok(ReturnSuccess::Value(out))]).to_output_stream())
+            }
+            IsEmptyFor::RowWithField(field) => {
+                let val =
+                    value.get_data_by_column_path(&field, Box::new(move |(_, _, err)| err))?;
+
+                let stream = match &value {
+                    obj
+                    @
+                    Value {
+                        value: UntaggedValue::Row(_),
+                        ..
+                    } => {
+                        if val.is_empty() {
+                            match obj.replace_data_at_column_path(
+                                &field,
+                                UntaggedValue::boolean(true).into_value(&value_tag),
+                            ) {
+                                Some(v) => futures::stream::iter(vec![Ok(ReturnSuccess::Value(v))]),
+                                None => {
+                                    return Err(ShellError::labeled_error(
+                                        "empty? could not find place to check emptiness",
+                                        "column name",
+                                        &field.tag,
+                                    ))
+                                }
+                            }
+                        } else {
+                            futures::stream::iter(vec![Ok(ReturnSuccess::Value(value))])
+                        }
+                    }
+                    _ => {
+                        return Err(ShellError::labeled_error(
+                            "Unrecognized type in stream",
+                            "original value",
+                            &value_tag,
+                        ))
+                    }
+                };
+
+                Ok(stream.to_output_stream())
+            }
+            IsEmptyFor::RowWithFieldAndFallback(field, default) => {
+                let val =
+                    value.get_data_by_column_path(&field, Box::new(move |(_, _, err)| err))?;
+
+                let stream = match &value {
+                    obj
+                    @
+                    Value {
+                        value: UntaggedValue::Row(_),
+                        ..
+                    } => {
+                        if val.is_empty() {
+                            match obj.replace_data_at_column_path(&field, default) {
+                                Some(v) => futures::stream::iter(vec![Ok(ReturnSuccess::Value(v))]),
+                                None => {
+                                    return Err(ShellError::labeled_error(
+                                        "empty? could not find place to check emptiness",
+                                        "column name",
+                                        &field.tag,
+                                    ))
+                                }
+                            }
+                        } else {
+                            futures::stream::iter(vec![Ok(ReturnSuccess::Value(value))])
+                        }
+                    }
+                    _ => {
+                        return Err(ShellError::labeled_error(
+                            "Unrecognized type in stream",
+                            "original value",
+                            &value_tag,
+                        ))
+                    }
+                };
+
+                Ok(stream.to_output_stream())
+            }
+        }
+    }
+}

crates/nu-cli/src/env/environment_syncer.rs

@@ -58,7 +58,7 @@ impl EnvironmentSyncer {
             }
 
             if let Some(variables) = environment.env() {
-                for var in nu_value_ext::row_entries(&variables) {
+                for var in variables.row_entries() {
                     if let Ok(string) = var.1.as_string() {
                         ctx.with_host(|host| {
                             host.env_set(
@@ -88,7 +88,8 @@ impl EnvironmentSyncer {
 
             if let Some(new_paths) = environment.path() {
                 let prepared = std::env::join_paths(
-                    nu_value_ext::table_entries(&new_paths)
+                    new_paths
+                        .table_entries()
                         .map(|p| p.as_string())
                         .filter_map(Result::ok),
                 );
@@ -212,9 +213,10 @@ mod tests {
             // including the newer one accounted for.
             let environment = actual.env.lock();
 
-            let vars = nu_value_ext::row_entries(
+            let vars = environment
-                &environment.env().expect("No variables in the environment."),
+                .env()
-            )
+                .expect("No variables in the environment.")
+                .row_entries()
                 .map(|(name, value)| {
                     (
                         name.to_string(),
@@ -281,9 +283,10 @@ mod tests {
 
             let environment = actual.env.lock();
 
-            let vars = nu_value_ext::row_entries(
+            let vars = environment
-                &environment.env().expect("No variables in the environment."),
+                .env()
-            )
+                .expect("No variables in the environment.")
+                .row_entries()
                 .map(|(name, value)| {
                     (
                         name.to_string(),
@@ -367,11 +370,10 @@ mod tests {
             let environment = actual.env.lock();
 
             let paths = std::env::join_paths(
-                &nu_value_ext::table_entries(
                 &environment
                     .path()
-                        .expect("No path variable in the environment."),
+                    .expect("No path variable in the environment.")
-                )
+                    .table_entries()
                     .map(|value| value.as_string().expect("Couldn't convert to string"))
                     .map(PathBuf::from)
                     .collect::<Vec<_>>(),
@@ -442,11 +444,10 @@ mod tests {
             let environment = actual.env.lock();
 
             let paths = std::env::join_paths(
-                &nu_value_ext::table_entries(
                 &environment
                     .path()
-                        .expect("No path variable in the environment."),
+                    .expect("No path variable in the environment.")
-                )
+                    .table_entries()
                     .map(|value| value.as_string().expect("Couldn't convert to string"))
                     .map(PathBuf::from)
                     .collect::<Vec<_>>(),

crates/nu-cli/src/utils.rs

@@ -69,7 +69,7 @@ impl ValueStructure {
     }
 
     fn build(&mut self, src: &Value, lvl: usize) -> Result<(), ShellError> {
-        for entry in nu_value_ext::row_entries(src) {
+        for entry in src.row_entries() {
             let value = entry.1;
             let path = entry.0;
 

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

@@ -0,0 +1,96 @@
+use nu_test_support::fs::Stub::FileWithContentToBeTrimmed;
+use nu_test_support::playground::Playground;
+use nu_test_support::{nu, pipeline};
+
+#[test]
+fn adds_value_provided_if_column_is_empty() {
+    Playground::setup("is_empty_test_1", |dirs, sandbox| {
+        sandbox.with_files(vec![FileWithContentToBeTrimmed(
+            "likes.csv",
+            r#"
+                first_name,last_name,rusty_at,likes
+                Andrés,Robalino,10/11/2013,1
+                Jonathan,Turner,10/12/2013,1
+                Jason,Gedge,10/11/2013,1
+                Yehuda,Katz,10/11/2013,
+            "#,
+        )]);
+
+        let actual = nu!(
+            cwd: dirs.test(), pipeline(
+            r#"
+                open likes.csv
+                | empty? likes 1
+                | get likes
+                | sum
+                | echo $it
+            "#
+        ));
+
+        assert_eq!(actual, "4");
+    })
+}
+
+#[test]
+fn adds_value_provided_for_columns_that_are_empty() {
+    Playground::setup("is_empty_test_2", |dirs, sandbox| {
+        sandbox.with_files(vec![FileWithContentToBeTrimmed(
+            "checks.json",
+            r#"
+                [
+                    {"boost": 1, "check": []},
+                    {"boost": 1, "check": ""},
+                    {"boost": 1, "check": {}},
+                    {"boost": null, "check": ["" {} [] ""]}
+                ]
+                
+            "#,
+        )]);
+
+        let actual = nu!(
+            cwd: dirs.test(), pipeline(
+            r#"
+                open checks.json
+                | empty? boost check 1
+                | get boost check
+                | sum
+                | echo $it
+            "#
+        ));
+
+        assert_eq!(actual, "8");
+    })
+}
+
+#[test]
+fn value_emptiness_check() {
+    Playground::setup("is_empty_test_3", |dirs, sandbox| {
+        sandbox.with_files(vec![FileWithContentToBeTrimmed(
+            "checks.json",
+            r#"
+                {
+                    "are_empty": [
+                        {"check": []},
+                        {"check": ""},
+                        {"check": {}},
+                        {"check": ["" {} [] ""]}
+                    ]
+                }
+            "#,
+        )]);
+
+        let actual = nu!(
+            cwd: dirs.test(), pipeline(
+            r#"
+                open checks.json
+                | get are_empty.check
+                | empty?
+                | where $it
+                | count
+                | echo $it
+            "#
+        ));
+
+        assert_eq!(actual, "4");
+    })
+}

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

@@ -16,6 +16,7 @@ mod group_by;
 mod headers;
 mod histogram;
 mod insert;
+mod is_empty;
 mod last;
 mod lines;
 mod ls;

crates/nu-protocol/src/value.rs

@@ -3,6 +3,7 @@ mod convert;
 mod debug;
 pub mod dict;
 pub mod evaluate;
+pub mod iter;
 pub mod primitive;
 pub mod range;
 mod serde_bigdecimal;
@@ -11,6 +12,7 @@ mod serde_bigint;
 use crate::hir;
 use crate::type_name::{ShellTypeName, SpannedTypeName};
 use crate::value::dict::Dictionary;
+use crate::value::iter::{RowValueIter, TableValueIter};
 use crate::value::primitive::Primitive;
 use crate::value::range::{Range, RangeInclusion};
 use crate::{ColumnPath, PathMember};
@@ -313,6 +315,39 @@ impl Value {
             _ => Err(ShellError::type_error("boolean", self.spanned_type_name())),
         }
     }
+
+    /// Returns an iterator of the values rows
+    pub fn table_entries(&self) -> TableValueIter<'_> {
+        crate::value::iter::table_entries(&self)
+    }
+
+    /// Returns an iterator of the value's cells
+    pub fn row_entries(&self) -> RowValueIter<'_> {
+        crate::value::iter::row_entries(&self)
+    }
+
+    /// Returns true if the value is empty
+    pub fn is_empty(&self) -> bool {
+        match &self {
+            Value {
+                value: UntaggedValue::Primitive(p),
+                ..
+            } => p.is_empty(),
+            t
+            @
+            Value {
+                value: UntaggedValue::Table(_),
+                ..
+            } => t.table_entries().all(|row| row.is_empty()),
+            r
+            @
+            Value {
+                value: UntaggedValue::Row(_),
+                ..
+            } => r.row_entries().all(|(_, value)| value.is_empty()),
+            _ => false,
+        }
+    }
 }
 
 impl Into<Value> for String {

crates/nu-protocol/src/value/iter.rs

@@ -0,0 +1,50 @@
+use crate::value::{UntaggedValue, Value};
+
+pub enum RowValueIter<'a> {
+    Empty,
+    Entries(indexmap::map::Iter<'a, String, Value>),
+}
+
+pub enum TableValueIter<'a> {
+    Empty,
+    Entries(std::slice::Iter<'a, Value>),
+}
+
+impl<'a> Iterator for RowValueIter<'a> {
+    type Item = (&'a String, &'a Value);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        match self {
+            RowValueIter::Empty => None,
+            RowValueIter::Entries(iter) => iter.next(),
+        }
+    }
+}
+
+impl<'a> Iterator for TableValueIter<'a> {
+    type Item = &'a Value;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        match self {
+            TableValueIter::Empty => None,
+            TableValueIter::Entries(iter) => iter.next(),
+        }
+    }
+}
+
+pub fn table_entries(value: &Value) -> TableValueIter<'_> {
+    match &value.value {
+        UntaggedValue::Table(t) => TableValueIter::Entries(t.iter()),
+        _ => TableValueIter::Empty,
+    }
+}
+
+pub fn row_entries(value: &Value) -> RowValueIter<'_> {
+    match &value.value {
+        UntaggedValue::Row(o) => {
+            let iter = o.entries.iter();
+            RowValueIter::Entries(iter)
+        }
+        _ => RowValueIter::Empty,
+    }
+}

crates/nu-protocol/src/value/primitive.rs

@@ -84,6 +84,15 @@ impl Primitive {
             )),
         }
     }
+
+    /// Returns true if the value is empty
+    pub fn is_empty(&self) -> bool {
+        match self {
+            Primitive::Nothing => true,
+            Primitive::String(s) => s.is_empty(),
+            _ => false,
+        }
+    }
 }
 
 impl num_traits::Zero for Primitive {

crates/nu-value-ext/src/lib.rs

@@ -8,8 +8,6 @@ use nu_source::{HasSpan, PrettyDebug, Spanned, SpannedItem, Tag, Tagged, TaggedI
 use num_traits::cast::ToPrimitive;
 
 pub trait ValueExt {
-    fn row_entries(&self) -> RowValueIter<'_>;
-    fn table_entries(&self) -> TableValueIter<'_>;
     fn into_parts(self) -> (UntaggedValue, Tag);
     fn get_data(&self, desc: &str) -> MaybeOwned<'_, Value>;
     fn get_data_by_key(&self, name: Spanned<&str>) -> Option<Value>;
@@ -41,14 +39,6 @@ pub trait ValueExt {
 }
 
 impl ValueExt for Value {
-    fn row_entries(&self) -> RowValueIter<'_> {
-        row_entries(self)
-    }
-
-    fn table_entries(&self) -> TableValueIter<'_> {
-        table_entries(self)
-    }
-
     fn into_parts(self) -> (UntaggedValue, Tag) {
         (self.value, self.tag)
     }
@@ -534,52 +524,3 @@ pub(crate) fn get_mut_data_by_member<'value>(
         _ => None,
     }
 }
-
-pub enum RowValueIter<'a> {
-    Empty,
-    Entries(indexmap::map::Iter<'a, String, Value>),
-}
-
-pub enum TableValueIter<'a> {
-    Empty,
-    Entries(std::slice::Iter<'a, Value>),
-}
-
-impl<'a> Iterator for RowValueIter<'a> {
-    type Item = (&'a String, &'a Value);
-
-    fn next(&mut self) -> Option<Self::Item> {
-        match self {
-            RowValueIter::Empty => None,
-            RowValueIter::Entries(iter) => iter.next(),
-        }
-    }
-}
-
-impl<'a> Iterator for TableValueIter<'a> {
-    type Item = &'a Value;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        match self {
-            TableValueIter::Empty => None,
-            TableValueIter::Entries(iter) => iter.next(),
-        }
-    }
-}
-
-pub fn table_entries(value: &Value) -> TableValueIter<'_> {
-    match &value.value {
-        UntaggedValue::Table(t) => TableValueIter::Entries(t.iter()),
-        _ => TableValueIter::Empty,
-    }
-}
-
-pub fn row_entries(value: &Value) -> RowValueIter<'_> {
-    match &value.value {
-        UntaggedValue::Row(o) => {
-            let iter = o.entries.iter();
-            RowValueIter::Entries(iter)
-        }
-        _ => RowValueIter::Empty,
-    }
-}