feat: add support for YAML and JSON to the generate command (vectordotdev#18345)

* feat: add support for YAML and JSON to the generate command

* tweaks and pretty print

* delete comments

* more tests

Author: pront

src/config/cmd.rs

@@ -202,8 +202,10 @@ mod tests {
     use serde_json::json;
     use vector_config::component::{SinkDescription, SourceDescription, TransformDescription};
 
+    use crate::config::Format;
     use crate::{
         config::{cmd::serialize_to_json, vars, ConfigBuilder},
+        generate,
         generate::{generate_example, TransformInputsStrategy},
     };
 
@@ -325,13 +327,13 @@ mod tests {
                 .collect::<Vec<_>>()
                 .join(","),
         );
-        generate_example(
-            false,
-            generate_config_str.as_ref(),
-            &None,
-            TransformInputsStrategy::All,
-        )
-        .expect("invalid config generated")
+        let opts = generate::Opts {
+            fragment: true,
+            expression: generate_config_str.to_string(),
+            file: None,
+            format: Format::Toml,
+        };
+        generate_example(&opts, TransformInputsStrategy::All).expect("invalid config generated")
     }
 
     proptest! {

src/config/format.rs

@@ -3,6 +3,7 @@
 #![deny(missing_docs, missing_debug_implementations)]
 
 use std::path::Path;
+use std::str::FromStr;
 
 use serde::de;
 
@@ -21,6 +22,19 @@ pub enum Format {
     Yaml,
 }
 
+impl FromStr for Format {
+    type Err = String;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s.to_lowercase().as_str() {
+            "toml" => Ok(Format::Toml),
+            "yaml" => Ok(Format::Yaml),
+            "json" => Ok(Format::Json),
+            _ => Err(format!("Invalid format: {}", s)),
+        }
+    }
+}
+
 impl Format {
     /// Obtain the format from the file path using extension as a hint.
     pub fn from_path<T: AsRef<Path>>(path: T) -> Result<Self, T> {
@@ -34,8 +48,6 @@ impl Format {
 }
 
 /// Parse the string represented in the specified format.
-/// If the format is unknown - fallback to the default format and attempt
-/// parsing using that.
 pub fn deserialize<T>(content: &str, format: Format) -> Result<T, Vec<String>>
 where
     T: de::DeserializeOwned,
@@ -47,9 +59,31 @@ where
     }
 }
 
+/// Serialize the specified `value` into a string.
+pub fn serialize<T>(value: &T, format: Format) -> Result<String, String>
+where
+    T: serde::ser::Serialize,
+{
+    match format {
+        Format::Toml => toml::to_string(value).map_err(|e| e.to_string()),
+        Format::Yaml => serde_yaml::to_string(value).map_err(|e| e.to_string()),
+        Format::Json => serde_json::to_string_pretty(value).map_err(|e| e.to_string()),
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
+    use proptest::prelude::*;
+
+    impl Arbitrary for Format {
+        type Parameters = ();
+        fn arbitrary_with(_args: Self::Parameters) -> Self::Strategy {
+            prop_oneof![Just(Format::Toml), Just(Format::Json), Just(Format::Yaml),].boxed()
+        }
+
+        type Strategy = BoxedStrategy<Self>;
+    }
 
     /// This test ensures the logic to guess file format from the file path
     /// works correctly.