setting content type metadata on all core to * commands (#13506)

# Description

All core `to *` set content type pipeline metadata. 

# User-Facing Changes
- For consistency, `from json` no longer sets the content type metadata

# Tests + Formatting
- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib

crates/nu-cmd-lang/src/example_support.rs

@@ -72,7 +72,7 @@ pub fn check_example_input_and_output_types_match_command_signature(
     witnessed_type_transformations
 }
 
-fn eval_pipeline_without_terminal_expression(
+pub fn eval_pipeline_without_terminal_expression(
     src: &str,
     cwd: &std::path::Path,
     engine_state: &mut Box<EngineState>,

crates/nu-command/src/formats/from/json.rs

@@ -1,7 +1,7 @@
 use std::io::{BufRead, Cursor};
 
 use nu_engine::command_prelude::*;
-use nu_protocol::{ListStream, PipelineMetadata, Signals};
+use nu_protocol::{ListStream, Signals};
 
 #[derive(Clone)]
 pub struct FromJson;
@@ -83,7 +83,7 @@ impl Command for FromJson {
                             strict,
                             engine_state.signals().clone(),
                         ),
-                        update_metadata(metadata),
+                        metadata,
                     ))
                 }
                 PipelineData::ByteStream(stream, metadata)
@@ -92,7 +92,7 @@ impl Command for FromJson {
                     if let Some(reader) = stream.reader() {
                         Ok(PipelineData::ListStream(
                             read_json_lines(reader, span, strict, Signals::empty()),
-                            update_metadata(metadata),
+                            metadata,
                         ))
                     } else {
                         Ok(PipelineData::Empty)
@@ -115,10 +115,10 @@ impl Command for FromJson {
 
             if strict {
                 Ok(convert_string_to_value_strict(&string_input, span)?
-                    .into_pipeline_data_with_metadata(update_metadata(metadata)))
+                    .into_pipeline_data_with_metadata(metadata))
             } else {
                 Ok(convert_string_to_value(&string_input, span)?
-                    .into_pipeline_data_with_metadata(update_metadata(metadata)))
+                    .into_pipeline_data_with_metadata(metadata))
             }
         }
     }
@@ -265,14 +265,6 @@ fn convert_string_to_value_strict(string_input: &str, span: Span) -> Result<Valu
     }
 }
 
-fn update_metadata(metadata: Option<PipelineMetadata>) -> Option<PipelineMetadata> {
-    metadata
-        .map(|md| md.with_content_type(Some("application/json".into())))
-        .or_else(|| {
-            Some(PipelineMetadata::default().with_content_type(Some("application/json".into())))
-        })
-}
-
 #[cfg(test)]
 mod test {
     use super::*;

crates/nu-command/src/formats/to/csv.rs

@@ -4,6 +4,8 @@ use crate::formats::to::delimited::to_delimited_data;
 use nu_engine::command_prelude::*;
 use nu_protocol::Config;
 
+use super::delimited::ToDelimitedDataArgs;
+
 #[derive(Clone)]
 pub struct ToCsv;
 
@@ -116,17 +118,62 @@ fn to_csv(
         },
     };
 
-    to_delimited_data(noheaders, sep, columns, "CSV", input, head, config)
+    to_delimited_data(
+        ToDelimitedDataArgs {
+            noheaders,
+            separator: sep,
+            columns,
+            format_name: "CSV",
+            input,
+            head,
+            content_type: Some(mime::TEXT_CSV.to_string()),
+        },
+        config,
+    )
 }
 
 #[cfg(test)]
 mod test {
+
+    use nu_cmd_lang::eval_pipeline_without_terminal_expression;
+
+    use crate::Metadata;
+
     use super::*;
 
     #[test]
     fn test_examples() {
         use crate::test_examples;
-
         test_examples(ToCsv {})
     }
+
+    #[test]
+    fn test_content_type_metadata() {
+        let mut engine_state = Box::new(EngineState::new());
+        let delta = {
+            // Base functions that are needed for testing
+            // Try to keep this working set small to keep tests running as fast as possible
+            let mut working_set = StateWorkingSet::new(&engine_state);
+
+            working_set.add_decl(Box::new(ToCsv {}));
+            working_set.add_decl(Box::new(Metadata {}));
+
+            working_set.render()
+        };
+
+        engine_state
+            .merge_delta(delta)
+            .expect("Error merging delta");
+
+        let cmd = "{a: 1 b: 2} | to csv  | metadata | get content_type";
+        let result = eval_pipeline_without_terminal_expression(
+            cmd,
+            std::env::temp_dir().as_ref(),
+            &mut engine_state,
+        );
+        assert_eq!(
+            Value::test_record(record!("content_type" => Value::test_string("text/csv"))),
+            result.expect("There should be a result")
+        );
+    }
 }

crates/nu-command/src/formats/to/delimited.rs

@@ -69,18 +69,36 @@ fn make_cant_convert_error(value: &Value, format_name: &'static str) -> ShellErr
     }
 }
 
+pub struct ToDelimitedDataArgs {
+    pub noheaders: bool,
+    pub separator: Spanned<char>,
+    pub columns: Option<Vec<String>>,
+    pub format_name: &'static str,
+    pub input: PipelineData,
+    pub head: Span,
+    pub content_type: Option<String>,
+}
+
 pub fn to_delimited_data(
-    noheaders: bool,
+    ToDelimitedDataArgs {
-    separator: Spanned<char>,
+        noheaders,
-    columns: Option<Vec<String>>,
+        separator,
-    format_name: &'static str,
+        columns,
-    input: PipelineData,
+        format_name,
-    head: Span,
+        input,
+        head,
+        content_type,
+    }: ToDelimitedDataArgs,
     config: Arc<Config>,
 ) -> Result<PipelineData, ShellError> {
     let mut input = input;
     let span = input.span().unwrap_or(head);
-    let metadata = input.metadata();
+    let metadata = Some(
+        input
+            .metadata()
+            .unwrap_or_default()
+            .with_content_type(content_type),
+    );
 
     let separator = u8::try_from(separator.item).map_err(|_| ShellError::IncorrectValue {
         msg: "separator must be an ASCII character".into(),

crates/nu-command/src/formats/to/json.rs

@@ -64,7 +64,7 @@ impl Command for ToJson {
                 let res = Value::string(serde_json_string, span);
                 let metadata = PipelineMetadata {
                     data_source: nu_protocol::DataSource::None,
-                    content_type: Some("application/json".to_string()),
+                    content_type: Some(mime::APPLICATION_JSON.to_string()),
                 };
                 Ok(PipelineData::Value(res, Some(metadata)))
             }
@@ -159,6 +159,10 @@ fn json_list(input: &[Value]) -> Result<Vec<nu_json::Value>, ShellError> {
 
 #[cfg(test)]
 mod test {
+    use nu_cmd_lang::eval_pipeline_without_terminal_expression;
+
+    use crate::Metadata;
+
     use super::*;
 
     #[test]
@@ -167,4 +171,34 @@ mod test {
 
         test_examples(ToJson {})
     }
+
+    #[test]
+    fn test_content_type_metadata() {
+        let mut engine_state = Box::new(EngineState::new());
+        let delta = {
+            // Base functions that are needed for testing
+            // Try to keep this working set small to keep tests running as fast as possible
+            let mut working_set = StateWorkingSet::new(&engine_state);
+
+            working_set.add_decl(Box::new(ToJson {}));
+            working_set.add_decl(Box::new(Metadata {}));
+
+            working_set.render()
+        };
+
+        engine_state
+            .merge_delta(delta)
+            .expect("Error merging delta");
+
+        let cmd = "{a: 1 b: 2} | to json  | metadata | get content_type";
+        let result = eval_pipeline_without_terminal_expression(
+            cmd,
+            std::env::temp_dir().as_ref(),
+            &mut engine_state,
+        );
+        assert_eq!(
+            Value::test_record(record!("content_type" => Value::test_string("application/json"))),
+            result.expect("There should be a result")
+        );
+    }
 }

crates/nu-command/src/formats/to/md.rs

@@ -82,6 +82,12 @@ fn to_md(
     config: &Config,
     head: Span,
 ) -> Result<PipelineData, ShellError> {
+    // text/markdown became a valid mimetype with rfc7763
+    let metadata = input
+        .metadata()
+        .unwrap_or_default()
+        .with_content_type(Some("text/markdown".into()));
+
     let (grouped_input, single_list) = group_by(input, head, config);
     if per_element || single_list {
         return Ok(Value::string(
@@ -95,9 +101,10 @@ fn to_md(
                 .join(""),
             head,
         )
-        .into_pipeline_data());
+        .into_pipeline_data_with_metadata(Some(metadata)));
     }
-    Ok(Value::string(table(grouped_input, pretty, config), head).into_pipeline_data())
+    Ok(Value::string(table(grouped_input, pretty, config), head)
+        .into_pipeline_data_with_metadata(Some(metadata)))
 }
 
 fn fragment(input: Value, pretty: bool, config: &Config) -> String {
@@ -328,7 +335,10 @@ fn get_padded_string(text: String, desired_length: usize, padding_character: cha
 
 #[cfg(test)]
 mod tests {
+    use crate::Metadata;
+
     use super::*;
+    use nu_cmd_lang::eval_pipeline_without_terminal_expression;
     use nu_protocol::{record, Config, IntoPipelineData, Value};
 
     fn one(string: &str) -> String {
@@ -453,4 +463,35 @@ mod tests {
         "#)
         );
     }
+
+    #[test]
+    fn test_content_type_metadata() {
+        let mut engine_state = Box::new(EngineState::new());
+        let state_delta = {
+            // Base functions that are needed for testing
+            // Try to keep this working set small to keep tests running as fast as possible
+            let mut working_set = StateWorkingSet::new(&engine_state);
+
+            working_set.add_decl(Box::new(ToMd {}));
+            working_set.add_decl(Box::new(Metadata {}));
+
+            working_set.render()
+        };
+        let delta = state_delta;
+
+        engine_state
+            .merge_delta(delta)
+            .expect("Error merging delta");
+
+        let cmd = "{a: 1 b: 2} | to md  | metadata | get content_type";
+        let result = eval_pipeline_without_terminal_expression(
+            cmd,
+            std::env::temp_dir().as_ref(),
+            &mut engine_state,
+        );
+        assert_eq!(
+            Value::test_record(record!("content_type" => Value::test_string("text/markdown"))),
+            result.expect("There should be a result")
+        );
+    }
 }

crates/nu-command/src/formats/to/msgpack.rs

@@ -74,13 +74,18 @@ MessagePack: https://msgpack.org/
         call: &Call,
         input: PipelineData,
     ) -> Result<PipelineData, ShellError> {
+        let metadata = input
+            .metadata()
+            .unwrap_or_default()
+            .with_content_type(Some("application/x-msgpack".into()));
+
         let value_span = input.span().unwrap_or(call.head);
         let value = input.into_value(value_span)?;
         let mut out = vec![];
 
         write_value(&mut out, &value, 0)?;
 
-        Ok(Value::binary(out, call.head).into_pipeline_data())
+        Ok(Value::binary(out, call.head).into_pipeline_data_with_metadata(Some(metadata)))
     }
 }
 
@@ -268,6 +273,10 @@ where
 
 #[cfg(test)]
 mod test {
+    use nu_cmd_lang::eval_pipeline_without_terminal_expression;
+
+    use crate::Metadata;
+
     use super::*;
 
     #[test]
@@ -276,4 +285,36 @@ mod test {
 
         test_examples(ToMsgpack {})
     }
+
+    #[test]
+    fn test_content_type_metadata() {
+        let mut engine_state = Box::new(EngineState::new());
+        let delta = {
+            // Base functions that are needed for testing
+            // Try to keep this working set small to keep tests running as fast as possible
+            let mut working_set = StateWorkingSet::new(&engine_state);
+
+            working_set.add_decl(Box::new(ToMsgpack {}));
+            working_set.add_decl(Box::new(Metadata {}));
+
+            working_set.render()
+        };
+
+        engine_state
+            .merge_delta(delta)
+            .expect("Error merging delta");
+
+        let cmd = "{a: 1 b: 2} | to msgpack | metadata | get content_type";
+        let result = eval_pipeline_without_terminal_expression(
+            cmd,
+            std::env::temp_dir().as_ref(),
+            &mut engine_state,
+        );
+        assert_eq!(
+            Value::test_record(
+                record!("content_type" => Value::test_string("application/x-msgpack"))
+            ),
+            result.expect("There should be a result")
+        );
+    }
 }

crates/nu-command/src/formats/to/nuon.rs

@@ -42,6 +42,11 @@ impl Command for ToNuon {
         call: &Call,
         input: PipelineData,
     ) -> Result<PipelineData, ShellError> {
+        let metadata = input
+            .metadata()
+            .unwrap_or_default()
+            .with_content_type(Some("application/x-nuon".into()));
+
         let style = if call.has_flag(engine_state, stack, "raw")? {
             nuon::ToStyle::Raw
         } else if let Some(t) = call.get_flag(engine_state, stack, "tabs")? {
@@ -56,9 +61,8 @@ impl Command for ToNuon {
         let value = input.into_value(span)?;
 
         match nuon::to_nuon(&value, style, Some(span)) {
-            Ok(serde_nuon_string) => {
+            Ok(serde_nuon_string) => Ok(Value::string(serde_nuon_string, span)
-                Ok(Value::string(serde_nuon_string, span).into_pipeline_data())
+                .into_pipeline_data_with_metadata(Some(metadata))),
-            }
             _ => Ok(Value::error(
                 ShellError::CantConvert {
                     to_type: "NUON".into(),
@@ -68,7 +72,7 @@ impl Command for ToNuon {
                 },
                 span,
             )
-            .into_pipeline_data()),
+            .into_pipeline_data_with_metadata(Some(metadata))),
         }
     }
 
@@ -100,10 +104,45 @@ impl Command for ToNuon {
 
 #[cfg(test)]
 mod test {
+    use super::*;
+    use nu_cmd_lang::eval_pipeline_without_terminal_expression;
+
+    use crate::Metadata;
+
     #[test]
     fn test_examples() {
         use super::ToNuon;
         use crate::test_examples;
         test_examples(ToNuon {})
     }
+
+    #[test]
+    fn test_content_type_metadata() {
+        let mut engine_state = Box::new(EngineState::new());
+        let delta = {
+            // Base functions that are needed for testing
+            // Try to keep this working set small to keep tests running as fast as possible
+            let mut working_set = StateWorkingSet::new(&engine_state);
+
+            working_set.add_decl(Box::new(ToNuon {}));
+            working_set.add_decl(Box::new(Metadata {}));
+
+            working_set.render()
+        };
+
+        engine_state
+            .merge_delta(delta)
+            .expect("Error merging delta");
+
+        let cmd = "{a: 1 b: 2} | to nuon | metadata | get content_type";
+        let result = eval_pipeline_without_terminal_expression(
+            cmd,
+            std::env::temp_dir().as_ref(),
+            &mut engine_state,
+        );
+        assert_eq!(
+            Value::test_record(record!("content_type" => Value::test_string("application/x-nuon"))),
+            result.expect("There should be a result")
+        );
+    }
 }

crates/nu-command/src/formats/to/text.rs

@@ -134,14 +134,18 @@ fn local_into_string(value: Value, separator: &str, config: &Config) -> String {
 
 fn update_metadata(metadata: Option<PipelineMetadata>) -> Option<PipelineMetadata> {
     metadata
-        .map(|md| md.with_content_type(Some("text/plain".to_string())))
+        .map(|md| md.with_content_type(Some(mime::TEXT_PLAIN.to_string())))
         .or_else(|| {
-            Some(PipelineMetadata::default().with_content_type(Some("text/plain".to_string())))
+            Some(PipelineMetadata::default().with_content_type(Some(mime::TEXT_PLAIN.to_string())))
         })
 }
 
 #[cfg(test)]
 mod test {
+    use nu_cmd_lang::eval_pipeline_without_terminal_expression;
+
+    use crate::Metadata;
+
     use super::*;
 
     #[test]
@@ -150,4 +154,34 @@ mod test {
 
         test_examples(ToText {})
     }
+
+    #[test]
+    fn test_content_type_metadata() {
+        let mut engine_state = Box::new(EngineState::new());
+        let delta = {
+            // Base functions that are needed for testing
+            // Try to keep this working set small to keep tests running as fast as possible
+            let mut working_set = StateWorkingSet::new(&engine_state);
+
+            working_set.add_decl(Box::new(ToText {}));
+            working_set.add_decl(Box::new(Metadata {}));
+
+            working_set.render()
+        };
+
+        engine_state
+            .merge_delta(delta)
+            .expect("Error merging delta");
+
+        let cmd = "{a: 1 b: 2} | to text  | metadata | get content_type";
+        let result = eval_pipeline_without_terminal_expression(
+            cmd,
+            std::env::temp_dir().as_ref(),
+            &mut engine_state,
+        );
+        assert_eq!(
+            Value::test_record(record!("content_type" => Value::test_string("text/plain"))),
+            result.expect("There should be a result")
+        );
+    }
 }

crates/nu-command/src/formats/to/tsv.rs

@@ -4,6 +4,8 @@ use crate::formats::to::delimited::to_delimited_data;
 use nu_engine::command_prelude::*;
 use nu_protocol::Config;
 
+use super::delimited::ToDelimitedDataArgs;
+
 #[derive(Clone)]
 pub struct ToTsv;
 
@@ -82,11 +84,26 @@ fn to_tsv(
         item: '\t',
         span: head,
     };
-    to_delimited_data(noheaders, sep, columns, "TSV", input, head, config)
+    to_delimited_data(
+        ToDelimitedDataArgs {
+            noheaders,
+            separator: sep,
+            columns,
+            format_name: "TSV",
+            input,
+            head,
+            content_type: Some(mime::TEXT_TAB_SEPARATED_VALUES.to_string()),
+        },
+        config,
+    )
 }
 
 #[cfg(test)]
 mod test {
+    use nu_cmd_lang::eval_pipeline_without_terminal_expression;
+
+    use crate::Metadata;
+
     use super::*;
 
     #[test]
@@ -95,4 +112,36 @@ mod test {
 
         test_examples(ToTsv {})
     }
+
+    #[test]
+    fn test_content_type_metadata() {
+        let mut engine_state = Box::new(EngineState::new());
+        let delta = {
+            // Base functions that are needed for testing
+            // Try to keep this working set small to keep tests running as fast as possible
+            let mut working_set = StateWorkingSet::new(&engine_state);
+
+            working_set.add_decl(Box::new(ToTsv {}));
+            working_set.add_decl(Box::new(Metadata {}));
+
+            working_set.render()
+        };
+
+        engine_state
+            .merge_delta(delta)
+            .expect("Error merging delta");
+
+        let cmd = "{a: 1 b: 2} | to tsv | metadata | get content_type";
+        let result = eval_pipeline_without_terminal_expression(
+            cmd,
+            std::env::temp_dir().as_ref(),
+            &mut engine_state,
+        );
+        assert_eq!(
+            Value::test_record(
+                record!("content_type" => Value::test_string("text/tab-separated-values"))
+            ),
+            result.expect("There should be a result")
+        );
+    }
 }

crates/nu-command/src/formats/to/xml.rs

@@ -132,6 +132,10 @@ impl Job {
     }
 
     fn run(mut self, input: PipelineData, head: Span) -> Result<PipelineData, ShellError> {
+        let metadata = input
+            .metadata()
+            .unwrap_or_default()
+            .with_content_type(Some("application/xml".into()));
         let value = input.into_value(head)?;
 
         self.write_xml_entry(value, true).and_then(|_| {
@@ -141,7 +145,7 @@ impl Job {
             } else {
                 return Err(ShellError::NonUtf8 { span: head });
             };
-            Ok(Value::string(s, head).into_pipeline_data())
+            Ok(Value::string(s, head).into_pipeline_data_with_metadata(Some(metadata)))
         })
     }
 
@@ -508,6 +512,10 @@ impl Job {
 
 #[cfg(test)]
 mod test {
+    use nu_cmd_lang::eval_pipeline_without_terminal_expression;
+
+    use crate::Metadata;
+
     use super::*;
 
     #[test]
@@ -516,4 +524,34 @@ mod test {
 
         test_examples(ToXml {})
     }
+
+    #[test]
+    fn test_content_type_metadata() {
+        let mut engine_state = Box::new(EngineState::new());
+        let delta = {
+            // Base functions that are needed for testing
+            // Try to keep this working set small to keep tests running as fast as possible
+            let mut working_set = StateWorkingSet::new(&engine_state);
+
+            working_set.add_decl(Box::new(ToXml {}));
+            working_set.add_decl(Box::new(Metadata {}));
+
+            working_set.render()
+        };
+
+        engine_state
+            .merge_delta(delta)
+            .expect("Error merging delta");
+
+        let cmd = "{tag: note attributes: {} content : [{tag: remember attributes: {} content : [{tag: null attributes: null content : Event}]}]} | to xml | metadata | get content_type";
+        let result = eval_pipeline_without_terminal_expression(
+            cmd,
+            std::env::temp_dir().as_ref(),
+            &mut engine_state,
+        );
+        assert_eq!(
+            Value::test_record(record!("content_type" => Value::test_string("application/xml"))),
+            result.expect("There should be a result")
+        );
+    }
 }

crates/nu-command/src/formats/to/yaml.rs

@@ -95,11 +95,18 @@ pub fn value_to_yaml_value(v: &Value) -> Result<serde_yaml::Value, ShellError> {
 }
 
 fn to_yaml(input: PipelineData, head: Span) -> Result<PipelineData, ShellError> {
+    let metadata = input
+        .metadata()
+        .unwrap_or_default()
+        .with_content_type(Some("application/yaml".into()));
     let value = input.into_value(head)?;
 
     let yaml_value = value_to_yaml_value(&value)?;
     match serde_yaml::to_string(&yaml_value) {
-        Ok(serde_yaml_string) => Ok(Value::string(serde_yaml_string, head).into_pipeline_data()),
+        Ok(serde_yaml_string) => {
+            Ok(Value::string(serde_yaml_string, head)
+                .into_pipeline_data_with_metadata(Some(metadata)))
+        }
         _ => Ok(Value::error(
             ShellError::CantConvert {
                 to_type: "YAML".into(),
@@ -109,12 +116,16 @@ fn to_yaml(input: PipelineData, head: Span) -> Result<PipelineData, ShellError>
             },
             head,
         )
-        .into_pipeline_data()),
+        .into_pipeline_data_with_metadata(Some(metadata))),
     }
 }
 
 #[cfg(test)]
 mod test {
+    use nu_cmd_lang::eval_pipeline_without_terminal_expression;
+
+    use crate::Metadata;
+
     use super::*;
 
     #[test]
@@ -123,4 +134,34 @@ mod test {
 
         test_examples(ToYaml {})
     }
+
+    #[test]
+    fn test_content_type_metadata() {
+        let mut engine_state = Box::new(EngineState::new());
+        let delta = {
+            // Base functions that are needed for testing
+            // Try to keep this working set small to keep tests running as fast as possible
+            let mut working_set = StateWorkingSet::new(&engine_state);
+
+            working_set.add_decl(Box::new(ToYaml {}));
+            working_set.add_decl(Box::new(Metadata {}));
+
+            working_set.render()
+        };
+
+        engine_state
+            .merge_delta(delta)
+            .expect("Error merging delta");
+
+        let cmd = "{a: 1 b: 2} | to yaml  | metadata | get content_type";
+        let result = eval_pipeline_without_terminal_expression(
+            cmd,
+            std::env::temp_dir().as_ref(),
+            &mut engine_state,
+        );
+        assert_eq!(
+            Value::test_record(record!("content_type" => Value::test_string("application/yaml"))),
+            result.expect("There should be a result")
+        );
+    }
 }