Declare input and output types of commands (#6796)

* Add failing test that list of ints and floats is List<Number>

* Start defining subtype relation

* Make it possible to declare input and output types for commands

- Enforce them in tests

* Declare input and output types of commands

* Add formatted signatures to `help commands` table

* Revert SyntaxShape::Table -> Type::Table change

* Revert unnecessary derive(Hash) on SyntaxShape

Co-authored-by: JT <547158+jntrnr@users.noreply.github.com>

crates/nu-command/src/strings/build_string.rs

@@ -3,7 +3,7 @@ use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
     Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Span, SyntaxShape,
-    Value,
+    Type, Value,
 };
 
 #[derive(Clone)]
@@ -25,6 +25,7 @@ impl Command for BuildString {
     fn signature(&self) -> nu_protocol::Signature {
         Signature::build("build-string")
             .rest("rest", SyntaxShape::String, "list of string")
+            .input_output_types(vec![(Type::Nothing, Type::String)])
             .category(Category::Strings)
     }
 

crates/nu-command/src/strings/char_.rs

@@ -4,7 +4,7 @@ use lazy_static::lazy_static;
 use nu_engine::CallExt;
 use nu_protocol::{
     ast::Call, engine::Command, Category, Example, IntoInterruptiblePipelineData, IntoPipelineData,
-    PipelineData, ShellError, Signature, Span, SyntaxShape, Value,
+    PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value,
 };
 
 // Character used to separate directories in a Path Environment variable on windows is ";"
@@ -156,6 +156,7 @@ impl Command for Char {
 
     fn signature(&self) -> Signature {
         Signature::build("char")
+            .input_output_types(vec![(Type::Nothing, Type::String)])
             .optional(
                 "character",
                 SyntaxShape::Any,

crates/nu-command/src/strings/detect_columns.rs

@@ -6,7 +6,7 @@ use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
     Category, Example, IntoInterruptiblePipelineData, PipelineData, ShellError, Signature, Span,
-    Spanned, SyntaxShape, Value,
+    Spanned, SyntaxShape, Type, Value,
 };
 
 type Input<'t> = Peekable<CharIndices<'t>>;
@@ -27,6 +27,7 @@ impl Command for DetectColumns {
                 "number of rows to skip before detecting",
                 Some('s'),
             )
+            .input_output_types(vec![(Type::String, Type::Table(vec![]))])
             .switch("no-headers", "don't detect headers", Some('n'))
             .category(Category::Strings)
     }

crates/nu-command/src/strings/encode_decode/decode.rs

@@ -3,7 +3,7 @@ use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
     Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Span, Spanned,
-    SyntaxShape, Value,
+    SyntaxShape, Type, Value,
 };
 
 #[derive(Clone)]
@@ -24,6 +24,7 @@ impl Command for Decode {
 
     fn signature(&self) -> nu_protocol::Signature {
         Signature::build("decode")
+            .input_output_types(vec![(Type::Binary, Type::String)])
             .required("encoding", SyntaxShape::String, "the text encoding to use")
             .category(Category::Strings)
     }

crates/nu-command/src/strings/encode_decode/decode_base64.rs

@@ -2,7 +2,7 @@ use super::base64::{operate, ActionType, CHARACTER_SET_DESC};
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
-    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value,
+    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value,
 };
 
 #[derive(Clone)]
@@ -15,6 +15,11 @@ impl Command for DecodeBase64 {
 
     fn signature(&self) -> Signature {
         Signature::build("decode base64")
+            .input_output_types(vec![
+                (Type::String, Type::String),
+                (Type::String, Type::Binary),
+            ])
+            .vectorizes_over_list(true)
             .named(
                 "character-set",
                 SyntaxShape::String,

crates/nu-command/src/strings/encode_decode/encode.rs

@@ -3,7 +3,7 @@ use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
     Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Span, Spanned,
-    SyntaxShape, Value,
+    SyntaxShape, Type, Value,
 };
 
 #[derive(Clone)]
@@ -24,6 +24,7 @@ impl Command for Encode {
 
     fn signature(&self) -> nu_protocol::Signature {
         Signature::build("encode")
+            .input_output_types(vec![(Type::String, Type::Binary)])
             .required("encoding", SyntaxShape::String, "the text encoding to use")
             .category(Category::Strings)
     }

crates/nu-command/src/strings/encode_decode/encode_base64.rs

@@ -15,6 +15,8 @@ impl Command for EncodeBase64 {
 
     fn signature(&self) -> Signature {
         Signature::build("encode base64")
+            .input_output_types(vec![(Type::String, Type::String)])
+            .vectorizes_over_list(true)
             .named(
                 "character-set",
                 SyntaxShape::String,

crates/nu-command/src/strings/format/command.rs

@@ -2,9 +2,9 @@ use nu_engine::{eval_expression, CallExt};
 use nu_parser::parse_expression;
 use nu_protocol::ast::{Call, PathMember};
 use nu_protocol::engine::{Command, EngineState, Stack, StateWorkingSet};
-use nu_protocol::Type;
 use nu_protocol::{
-    Category, Example, ListStream, PipelineData, ShellError, Signature, Span, SyntaxShape, Value,
+    Category, Example, ListStream, PipelineData, ShellError, Signature, Span, SyntaxShape, Type,
+    Value,
 };
 
 #[derive(Clone)]
@@ -17,6 +17,10 @@ impl Command for Format {
 
     fn signature(&self) -> Signature {
         Signature::build("format")
+            .input_output_types(vec![(
+                Type::Table(vec![]),
+                Type::List(Box::new(Type::String)),
+            )])
             .required(
                 "pattern",
                 SyntaxShape::String,

crates/nu-command/src/strings/format/filesize.rs

@@ -4,7 +4,7 @@ use nu_protocol::ast::{Call, CellPath};
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
     format_filesize, Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape,
-    Value,
+    Type, Value,
 };
 
 struct Arguments {
@@ -28,6 +28,7 @@ impl Command for FileSize {
 
     fn signature(&self) -> Signature {
         Signature::build("format filesize")
+            .input_output_types(vec![(Type::Filesize, Type::String)])
             .required(
                 "format value",
                 SyntaxShape::String,
@@ -36,7 +37,7 @@ impl Command for FileSize {
             .rest(
                 "rest",
                 SyntaxShape::CellPath,
-                "optinally find and replace text by column paths",
+                "Optionally find and replace text by column paths",
             )
             .category(Category::Strings)
     }
@@ -78,19 +79,19 @@ impl Command for FileSize {
     fn examples(&self) -> Vec<Example> {
         vec![
             Example {
-                description: "Convert the size row to KB",
+                description: "Convert the size column to KB",
                 example: "ls | format filesize KB size",
                 result: None,
             },
             Example {
-                description: "Convert the apparent row to B",
+                description: "Convert the apparent column to B",
                 example: "du | format filesize B apparent",
                 result: None,
             },
             Example {
                 description: "Convert the size data to MB",
                 example: "4Gb | format filesize MB",
-                result: None,
+                result: Some(Value::test_string("4000.0 MB")),
             },
         ]
     }

crates/nu-command/src/strings/parse.rs

@@ -4,7 +4,7 @@ use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
     Category, Example, ListStream, PipelineData, ShellError, Signature, Span, Spanned, SyntaxShape,
-    Value,
+    Type, Value,
 };
 
 #[derive(Clone)]
@@ -30,6 +30,7 @@ impl Command for Parse {
                 SyntaxShape::String,
                 "the pattern to match. Eg) \"{foo}: {bar}\"",
             )
+            .input_output_types(vec![(Type::String, Type::Table(vec![]))])
             .switch("regex", "use full regex syntax for patterns", Some('r'))
             .category(Category::Strings)
     }

crates/nu-command/src/strings/size.rs

@@ -1,7 +1,7 @@
 use fancy_regex::Regex;
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
-use nu_protocol::{Category, Example, PipelineData, ShellError, Signature, Span, Value};
+use nu_protocol::{Category, Example, PipelineData, ShellError, Signature, Span, Type, Value};
 use std::collections::BTreeMap;
 use std::{fmt, str};
 use unicode_segmentation::UnicodeSegmentation;
@@ -18,7 +18,9 @@ impl Command for Size {
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("size").category(Category::Strings)
+        Signature::build("size")
+            .category(Category::Strings)
+            .input_output_types(vec![(Type::String, Type::Record(vec![]))])
     }
 
     fn usage(&self) -> &str {

crates/nu-command/src/strings/split/chars.rs

@@ -1,7 +1,7 @@
 use nu_protocol::{
     ast::Call,
     engine::{Command, EngineState, Stack},
-    Category, Example, PipelineData, ShellError, Signature, Span, Value,
+    Category, Example, PipelineData, ShellError, Signature, Span, Type, Value,
 };
 
 #[derive(Clone)]
@@ -13,11 +13,14 @@ impl Command for SubCommand {
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("split chars").category(Category::Strings)
+        Signature::build("split chars")
+            .input_output_types(vec![(Type::String, Type::List(Box::new(Type::String)))])
+            .vectorizes_over_list(true)
+            .category(Category::Strings)
     }
 
     fn usage(&self) -> &str {
-        "Split a string's characters into separate rows"
+        "Split a string into a list of characters"
     }
 
     fn search_terms(&self) -> Vec<&str> {
@@ -26,7 +29,7 @@ impl Command for SubCommand {
 
     fn examples(&self) -> Vec<Example> {
         vec![Example {
-            description: "Split the string's characters into separate rows",
+            description: "Split the string into a list of characters",
             example: "'hello' | split chars",
             result: Some(Value::List {
                 vals: vec![

crates/nu-command/src/strings/split/column.rs

@@ -2,7 +2,8 @@ use nu_engine::CallExt;
 use nu_protocol::{
     ast::Call,
     engine::{Command, EngineState, Stack},
-    Category, Example, PipelineData, ShellError, Signature, Span, Spanned, SyntaxShape, Value,
+    Category, Example, PipelineData, ShellError, Signature, Span, Spanned, SyntaxShape, Type,
+    Value,
 };
 
 #[derive(Clone)]
@@ -15,6 +16,14 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("split column")
+            .input_output_types(vec![
+                (Type::String, Type::Table(vec![])),
+                (
+                    // TODO: no test coverage (is this behavior a bug or a feature?)
+                    Type::List(Box::new(Type::String)),
+                    Type::Table(vec![]),
+                ),
+            ])
             .required(
                 "separator",
                 SyntaxShape::String,
@@ -71,7 +80,7 @@ impl Command for SubCommand {
             },
             Example {
                 description: "Split a string into columns of char and remove the empty columns",
-                example: "echo 'abc' | split column -c ''",
+                example: "'abc' | split column -c ''",
                 result: Some(Value::List {
                     vals: vec![Value::Record {
                         cols: vec![
@@ -89,6 +98,25 @@ impl Command for SubCommand {
                     span: Span::test_data(),
                 }),
             },
+            Example {
+                description: "Split a list of strings into a table",
+                example: "['a-b' 'c-d'] | split column -",
+                result: Some(Value::List {
+                    vals: vec![
+                        Value::Record {
+                            cols: vec!["column1".to_string(), "column2".to_string()],
+                            vals: vec![Value::test_string("a"), Value::test_string("b")],
+                            span: Span::test_data(),
+                        },
+                        Value::Record {
+                            cols: vec!["column1".to_string(), "column2".to_string()],
+                            vals: vec![Value::test_string("c"), Value::test_string("d")],
+                            span: Span::test_data(),
+                        },
+                    ],
+                    span: Span::test_data(),
+                }),
+            },
         ]
     }
 }
@@ -161,15 +189,14 @@ fn split_column_helper(
     }
 }
 
-// #[cfg(test)]
-// mod tests {
-//     use super::ShellError;
-//     use super::SubCommand;
+#[cfg(test)]
+mod test {
+    use super::*;
 
-//     #[test]
-//     fn examples_work_as_expected() -> Result<(), ShellError> {
-//         use crate::examples::test as test_examples;
+    #[test]
+    fn test_examples() {
+        use crate::test_examples;
 
-//         test_examples(SubCommand {})
-//     }
-// }
+        test_examples(SubCommand {})
+    }
+}

crates/nu-command/src/strings/split/list.rs

@@ -2,7 +2,7 @@ use nu_engine::CallExt;
 use nu_protocol::{
     ast::Call,
     engine::{Command, EngineState, Stack},
-    Category, Example, IntoPipelineData, PipelineData, Signature, Span, SyntaxShape, Value,
+    Category, Example, IntoPipelineData, PipelineData, Signature, Span, SyntaxShape, Type, Value,
 };
 
 #[derive(Clone)]
@@ -15,6 +15,10 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("split list")
+            .input_output_types(vec![(
+                Type::List(Box::new(Type::Any)),
+                Type::List(Box::new(Type::List(Box::new(Type::Any)))),
+            )])
             .required(
                 "separator",
                 SyntaxShape::Any,
@@ -128,3 +132,15 @@ fn split_list(
     }
     .into_pipeline_data())
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_examples() {
+        use crate::test_examples;
+
+        test_examples(SubCommand {})
+    }
+}

crates/nu-command/src/strings/split/row.rs

@@ -2,7 +2,8 @@ use nu_engine::CallExt;
 use nu_protocol::{
     ast::Call,
     engine::{Command, EngineState, Stack},
-    Category, Example, PipelineData, ShellError, Signature, Span, Spanned, SyntaxShape, Value,
+    Category, Example, PipelineData, ShellError, Signature, Span, Spanned, SyntaxShape, Type,
+    Value,
 };
 
 #[derive(Clone)]
@@ -15,6 +16,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("split row")
+            .input_output_types(vec![(Type::String, Type::List(Box::new(Type::String)))])
+            .vectorizes_over_list(true)
             .required(
                 "separator",
                 SyntaxShape::String,
@@ -133,15 +136,14 @@ fn split_row_helper(
     }
 }
 
-// #[cfg(test)]
-// mod tests {
-//     use super::ShellError;
-//     use super::SubCommand;
+#[cfg(test)]
+mod test {
+    use super::*;
 
-//     #[test]
-//     fn examples_work_as_expected() -> Result<(), ShellError> {
-//         use crate::examples::test as test_examples;
+    #[test]
+    fn test_examples() {
+        use crate::test_examples;
 
-//         test_examples(SubCommand {})
-//     }
-// }
+        test_examples(SubCommand {})
+    }
+}

crates/nu-command/src/strings/split/words.rs

@@ -3,7 +3,7 @@ use nu_engine::CallExt;
 use nu_protocol::{
     ast::Call,
     engine::{Command, EngineState, Stack},
-    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value,
+    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value,
 };
 
 #[derive(Clone)]
@@ -16,6 +16,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("split words")
+            .input_output_types(vec![(Type::String, Type::List(Box::new(Type::String)))])
+            .vectorizes_over_list(true)
             .category(Category::Strings)
             // .switch(
             //     "ignore-hyphenated",

crates/nu-command/src/strings/str_/case/camel_case.rs

@@ -2,7 +2,7 @@ use inflector::cases::camelcase::to_camel_case;
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
-    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value,
+    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value,
 };
 
 use crate::operate;
@@ -17,6 +17,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str camel-case")
+            .input_output_types(vec![(Type::String, Type::String)])
+            .vectorizes_over_list(true)
             .rest(
                 "rest",
                 SyntaxShape::CellPath,

crates/nu-command/src/strings/str_/case/capitalize.rs

@@ -3,7 +3,7 @@ use nu_protocol::ast::Call;
 use nu_protocol::ast::CellPath;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::Category;
-use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value};
+use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value};
 
 #[derive(Clone)]
 pub struct SubCommand;
@@ -15,6 +15,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str capitalize")
+            .input_output_types(vec![(Type::String, Type::String)])
+            .vectorizes_over_list(true)
             .rest(
                 "rest",
                 SyntaxShape::CellPath,

crates/nu-command/src/strings/str_/case/downcase.rs

@@ -3,7 +3,7 @@ use nu_protocol::ast::Call;
 use nu_protocol::ast::CellPath;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::Category;
-use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value};
+use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value};
 
 #[derive(Clone)]
 pub struct SubCommand;
@@ -15,6 +15,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str downcase")
+            .input_output_types(vec![(Type::String, Type::String)])
+            .vectorizes_over_list(true)
             .rest(
                 "rest",
                 SyntaxShape::CellPath,

crates/nu-command/src/strings/str_/case/kebab_case.rs

@@ -2,7 +2,7 @@ use inflector::cases::kebabcase::to_kebab_case;
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
-    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value,
+    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value,
 };
 
 use crate::operate;
@@ -17,6 +17,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str kebab-case")
+            .input_output_types(vec![(Type::String, Type::String)])
+            .vectorizes_over_list(true)
             .rest(
                 "rest",
                 SyntaxShape::CellPath,

crates/nu-command/src/strings/str_/case/pascal_case.rs

@@ -2,7 +2,7 @@ use inflector::cases::pascalcase::to_pascal_case;
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
-    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value,
+    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value,
 };
 
 use crate::operate;
@@ -17,6 +17,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str pascal-case")
+            .input_output_types(vec![(Type::String, Type::String)])
+            .vectorizes_over_list(true)
             .rest(
                 "rest",
                 SyntaxShape::CellPath,

crates/nu-command/src/strings/str_/case/screaming_snake_case.rs

@@ -2,7 +2,7 @@ use inflector::cases::screamingsnakecase::to_screaming_snake_case;
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
-    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value,
+    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value,
 };
 
 use crate::operate;
@@ -16,6 +16,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str screaming-snake-case")
+            .input_output_types(vec![(Type::String, Type::String)])
+            .vectorizes_over_list(true)
             .rest(
                 "rest",
                 SyntaxShape::CellPath,

crates/nu-command/src/strings/str_/case/snake_case.rs

@@ -2,7 +2,7 @@ use inflector::cases::snakecase::to_snake_case;
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
-    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value,
+    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value,
 };
 
 use crate::operate;
@@ -16,6 +16,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str snake-case")
+            .input_output_types(vec![(Type::String, Type::String)])
+            .vectorizes_over_list(true)
             .rest(
                 "rest",
                 SyntaxShape::CellPath,

crates/nu-command/src/strings/str_/case/title_case.rs

@@ -2,7 +2,7 @@ use inflector::cases::titlecase::to_title_case;
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
-    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value,
+    Category, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value,
 };
 
 use crate::operate;
@@ -17,6 +17,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str title-case")
+            .input_output_types(vec![(Type::String, Type::String)])
+            .vectorizes_over_list(true)
             .rest(
                 "rest",
                 SyntaxShape::CellPath,

crates/nu-command/src/strings/str_/case/upcase.rs

@@ -2,7 +2,7 @@ use nu_engine::CallExt;
 use nu_protocol::ast::Call;
 use nu_protocol::ast::CellPath;
 use nu_protocol::engine::{Command, EngineState, Stack};
-use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value};
+use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value};
 
 #[derive(Clone)]
 pub struct SubCommand;
@@ -13,11 +13,14 @@ impl Command for SubCommand {
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("str upcase").rest(
-            "rest",
-            SyntaxShape::CellPath,
-            "optionally upcase text by column paths",
-        )
+        Signature::build("str upcase")
+            .input_output_types(vec![(Type::String, Type::String)])
+            .vectorizes_over_list(true)
+            .rest(
+                "rest",
+                SyntaxShape::CellPath,
+                "optionally upcase text by column paths",
+            )
     }
 
     fn usage(&self) -> &str {

crates/nu-command/src/strings/str_/collect.rs

@@ -3,7 +3,7 @@ use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
     Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Span, SyntaxShape,
-    Value,
+    Type, Value,
 };
 
 #[derive(Clone)]
@@ -16,6 +16,7 @@ impl Command for StrCollect {
 
     fn signature(&self) -> Signature {
         Signature::build("str collect")
+            .input_output_types(vec![(Type::List(Box::new(Type::String)), Type::String)])
             .optional(
                 "separator",
                 SyntaxShape::String,

crates/nu-command/src/strings/str_/contains.rs

@@ -4,7 +4,7 @@ use nu_protocol::ast::Call;
 use nu_protocol::ast::CellPath;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::Category;
-use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value};
+use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value};
 
 #[derive(Clone)]
 pub struct SubCommand;
@@ -29,6 +29,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str contains")
+            .input_output_types(vec![(Type::String, Type::Bool)])
+            .vectorizes_over_list(true)
             .required("string", SyntaxShape::String, "the string to find")
             .rest(
                 "rest",

crates/nu-command/src/strings/str_/distance.rs

@@ -4,7 +4,7 @@ use nu_protocol::{
     ast::{Call, CellPath},
     engine::{Command, EngineState, Stack},
     levenshtein_distance, Category, Example, PipelineData, ShellError, Signature, Span,
-    SyntaxShape, Value,
+    SyntaxShape, Type, Value,
 };
 
 #[derive(Clone)]
@@ -28,6 +28,7 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str distance")
+            .input_output_types(vec![(Type::String, Type::Int)])
             .required(
                 "compare-string",
                 SyntaxShape::String,
@@ -42,11 +43,11 @@ impl Command for SubCommand {
     }
 
     fn usage(&self) -> &str {
-        "compare two strings and return the edit distance/levenshtein distance"
+        "Compare two strings and return the edit distance/Levenshtein distance"
     }
 
     fn search_terms(&self) -> Vec<&str> {
-        vec!["edit", "match", "score", "levenshtein"]
+        vec!["edit", "levenshtein"]
     }
 
     fn run(
@@ -70,8 +71,19 @@ impl Command for SubCommand {
         vec![Example {
             description: "get the edit distance between two strings",
             example: "'nushell' | str distance 'nutshell'",
-            result: Some(Value::Int {
-                val: 1,
+            result: Some(Value::test_int(1)),
+        },
+        Example {
+            description: "Compute edit distance between strings in record and another string, using cell paths",
+            example: "[{a: 'nutshell' b: 'numetal'}] | str distance 'nushell' 'a' 'b'",
+            result: Some(Value::List {
+                vals: vec![
+                    Value::Record {
+                        cols: vec!["a".to_string(), "b".to_string()],
+                        vals: vec![Value::test_int(1), Value::test_int(4)],
+                        span: Span::test_data(),
+                    }
+                ],
                 span: Span::test_data(),
             }),
         }]

crates/nu-command/src/strings/str_/ends_with.rs

@@ -4,7 +4,7 @@ use nu_protocol::ast::Call;
 use nu_protocol::ast::CellPath;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::Category;
-use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value};
+use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value};
 
 struct Arguments {
     substring: String,
@@ -27,11 +27,13 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str ends-with")
+            .input_output_types(vec![(Type::String, Type::Bool)])
+            .vectorizes_over_list(true)
             .required("string", SyntaxShape::String, "the string to match")
             .rest(
                 "rest",
                 SyntaxShape::CellPath,
-                "optionally matches suffix of text by column paths",
+                "optionally matches suffix of text by cell paths",
             )
             .category(Category::Strings)
     }

crates/nu-command/src/strings/str_/index_of.rs

@@ -5,7 +5,7 @@ use nu_protocol::ast::CellPath;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::Category;
 use nu_protocol::Spanned;
-use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value};
+use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value};
 
 struct Arguments {
     end: bool,
@@ -33,6 +33,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str index-of")
+            .input_output_types(vec![(Type::String, Type::Int)])
+            .vectorizes_over_list(true) // TODO: no test coverage
             .required("string", SyntaxShape::String, "the string to find index of")
             .rest(
                 "rest",

crates/nu-command/src/strings/str_/join.rs

@@ -3,7 +3,7 @@ use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
     Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Span, SyntaxShape,
-    Value,
+    Type, Value,
 };
 
 #[derive(Clone)]
@@ -16,6 +16,7 @@ impl Command for StrJoin {
 
     fn signature(&self) -> Signature {
         Signature::build("str join")
+            .input_output_types(vec![(Type::List(Box::new(Type::String)), Type::String)])
             .optional(
                 "separator",
                 SyntaxShape::String,

crates/nu-command/src/strings/str_/length.rs

@@ -4,7 +4,7 @@ use nu_protocol::ast::Call;
 use nu_protocol::ast::CellPath;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::Category;
-use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value};
+use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value};
 #[derive(Clone)]
 pub struct SubCommand;
 
@@ -15,6 +15,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str length")
+            .input_output_types(vec![(Type::String, Type::Int)])
+            .vectorizes_over_list(true)
             .rest(
                 "rest",
                 SyntaxShape::CellPath,

crates/nu-command/src/strings/str_/lpad.rs

@@ -4,7 +4,7 @@ use nu_protocol::ast::Call;
 use nu_protocol::ast::CellPath;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::Category;
-use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value};
+use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value};
 
 struct Arguments {
     length: Option<i64>,
@@ -28,6 +28,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str lpad")
+            .input_output_types(vec![(Type::String, Type::String)])
+            .vectorizes_over_list(true)
             .required_named("length", SyntaxShape::Int, "length to pad to", Some('l'))
             .required_named(
                 "character",

crates/nu-command/src/strings/str_/replace.rs

@@ -4,7 +4,8 @@ use nu_engine::CallExt;
 use nu_protocol::{
     ast::{Call, CellPath},
     engine::{Command, EngineState, Stack},
-    Category, Example, PipelineData, ShellError, Signature, Span, Spanned, SyntaxShape, Value,
+    Category, Example, PipelineData, ShellError, Signature, Span, Spanned, SyntaxShape, Type,
+    Value,
 };
 
 struct Arguments {
@@ -32,6 +33,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str replace")
+            .input_output_types(vec![(Type::String, Type::String)])
+            .vectorizes_over_list(true)
             .required("find", SyntaxShape::String, "the pattern to find")
             .required("replace", SyntaxShape::String, "the replacement pattern")
             .rest(

crates/nu-command/src/strings/str_/reverse.rs

@@ -4,7 +4,7 @@ use nu_protocol::ast::Call;
 use nu_protocol::ast::CellPath;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::Category;
-use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value};
+use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value};
 
 #[derive(Clone)]
 pub struct SubCommand;
@@ -16,6 +16,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str reverse")
+            .input_output_types(vec![(Type::String, Type::String)])
+            .vectorizes_over_list(true)
             .rest(
                 "rest",
                 SyntaxShape::CellPath,

crates/nu-command/src/strings/str_/rpad.rs

@@ -4,7 +4,7 @@ use nu_protocol::ast::Call;
 use nu_protocol::ast::CellPath;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::Category;
-use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value};
+use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value};
 
 struct Arguments {
     length: Option<i64>,
@@ -28,6 +28,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str rpad")
+            .input_output_types(vec![(Type::String, Type::String)])
+            .vectorizes_over_list(true)
             .required_named("length", SyntaxShape::Int, "length to pad to", Some('l'))
             .required_named(
                 "character",

crates/nu-command/src/strings/str_/starts_with.rs

@@ -5,7 +5,7 @@ use nu_protocol::ast::CellPath;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::Category;
 use nu_protocol::Spanned;
-use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value};
+use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value};
 
 struct Arguments {
     substring: String,
@@ -29,6 +29,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str starts-with")
+            .input_output_types(vec![(Type::String, Type::Bool)])
+            .vectorizes_over_list(true)
             .required("string", SyntaxShape::String, "the string to match")
             .rest(
                 "rest",

crates/nu-command/src/strings/str_/substring.rs

@@ -3,7 +3,7 @@ use nu_engine::CallExt;
 use nu_protocol::ast::Call;
 use nu_protocol::ast::CellPath;
 use nu_protocol::engine::{Command, EngineState, Stack};
-use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value};
+use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Type, Value};
 use std::cmp::Ordering;
 
 #[derive(Clone)]
@@ -38,6 +38,8 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str substring")
+            .input_output_types(vec![(Type::String, Type::String)])
+            .vectorizes_over_list(true)
             .required(
                 "range",
                 SyntaxShape::Any,

crates/nu-command/src/strings/str_/trim/trim_.rs

@@ -4,7 +4,7 @@ use nu_engine::CallExt;
 use nu_protocol::{
     ast::{Call, CellPath},
     engine::{Command, EngineState, Stack},
-    Example, PipelineData, ShellError, Signature, Span, Spanned, SyntaxShape, Value,
+    Example, PipelineData, ShellError, Signature, Span, Spanned, SyntaxShape, Type, Value,
 };
 
 #[derive(Clone)]
@@ -39,7 +39,9 @@ impl Command for SubCommand {
 
     fn signature(&self) -> Signature {
         Signature::build("str trim")
-            .rest(
+        .input_output_types(vec![(Type::String, Type::String)])
+        .vectorizes_over_list(true)
+        .rest(
                 "rest",
                 SyntaxShape::CellPath,
                 "optionally trim text by column paths",