Render empty preview feature lists (#2546)

If the user has an empty list defined for preview features in their generator
block, do not remove the parameter when re-introspecting.

introspection-engine/introspection-engine-tests/tests/re_introspection/mod.rs

@@ -1781,7 +1781,7 @@ async fn re_introspecting_custom_compound_id_names(api: &TestApi) -> TestResult
 
              @@id([first, last], name: "compound", map: "User.something@invalid-and/weird")
          }
-         
+
          model User2 {
              first  Int
              last   Int
@@ -1798,7 +1798,7 @@ async fn re_introspecting_custom_compound_id_names(api: &TestApi) -> TestResult
 
              @@id([first, last], name: "compound", map: "User.something@invalid-and/weird")
          }
-         
+
          model User2 {
              first  Int
              last   Int

libs/datamodel/core/src/configuration/generator.rs

@@ -1,6 +1,6 @@
 use crate::{common::preview_features::PreviewFeature, configuration::StringFromEnvVar};
 use enumflags2::BitFlags;
-use serde::Serialize;
+use serde::{Serialize, Serializer};
 use std::collections::HashMap;
 
 #[derive(Debug, Serialize, Clone)]
@@ -14,15 +14,28 @@ pub struct Generator {
     #[serde(default)]
     pub binary_targets: Vec<StringFromEnvVar>,
 
-    #[serde(default)]
-    pub preview_features: Vec<PreviewFeature>,
+    #[serde(default, serialize_with = "mcf_preview_features")]
+    pub preview_features: Option<Vec<PreviewFeature>>,
 
     #[serde(skip_serializing_if = "Option::is_none")]
     pub documentation: Option<String>,
 }
 
+pub fn mcf_preview_features<S>(feat: &Option<Vec<PreviewFeature>>, s: S) -> Result<S::Ok, S::Error>
+where
+    S: Serializer,
+{
+    match feat {
+        Some(feats) => feats.serialize(s),
+        None => Vec::<String>::new().serialize(s),
+    }
+}
+
 impl Generator {
     pub fn preview_features(&self) -> BitFlags<PreviewFeature> {
-        self.preview_features.iter().copied().collect()
+        match self.preview_features {
+            Some(ref preview_features) => preview_features.iter().copied().collect(),
+            None => BitFlags::empty(),
+        }
     }
 }

libs/datamodel/core/src/lib.rs

@@ -289,8 +289,5 @@ fn render_schema_ast_to(stream: &mut dyn std::fmt::Write, schema: &ast::SchemaAs
 }
 
 fn preview_features(generators: &[Generator]) -> BitFlags<PreviewFeature> {
-    generators
-        .iter()
-        .flat_map(|gen| gen.preview_features.iter().cloned())
-        .collect()
+    generators.iter().map(|gen| gen.preview_features()).collect()
 }

libs/datamodel/core/src/transform/ast_to_dml/generator_loader.rs

@@ -1,6 +1,6 @@
 use super::super::helpers::*;
 use crate::{
-    ast::{self, Span, WithSpan},
+    ast::{self, WithSpan},
     common::preview_features::GENERATOR,
     configuration::Generator,
     diagnostics::*,
@@ -95,22 +95,18 @@ impl GeneratorLoader {
             .or_else(|| args.get(EXPERIMENTAL_FEATURES_KEY))
             .map(|v| (v.as_array().to_str_vec(), v.span()));
 
-        let (raw_preview_features, span) = match preview_features_arg {
-            Some((Ok(arr), span)) => (arr, span),
-            Some((Err(err), span)) => {
+        let preview_features = match preview_features_arg {
+            Some((Ok(arr), span)) => {
+                let (features, mut diag) = parse_and_validate_preview_features(arr, &GENERATOR, span);
+                diagnostics.append(&mut diag);
+
+                Some(features)
+            }
+            Some((Err(err), _)) => {
                 diagnostics.push_error(err);
-                (Vec::new(), span)
+                None
             }
-            None => (Vec::new(), Span::empty()),
-        };
-
-        let preview_features = if !raw_preview_features.is_empty() {
-            let (features, mut diag) = parse_and_validate_preview_features(raw_preview_features, &GENERATOR, span);
-            diagnostics.append(&mut diag);
-
-            features
-        } else {
-            vec![]
+            None => None,
         };
 
         for prop in &ast_generator.properties {

libs/datamodel/core/src/transform/dml_to_ast/generator_serializer.rs

@@ -17,38 +17,39 @@ impl GeneratorSerializer {
     }
 
     fn lower_generator(generator: &Generator) -> ast::GeneratorConfig {
-        let mut arguments: Vec<ast::Argument> = vec![super::lower_string_from_env_var("provider", &generator.provider)];
+        let mut properties: Vec<ast::Argument> =
+            vec![super::lower_string_from_env_var("provider", &generator.provider)];
 
         if let Some(output) = &generator.output {
-            arguments.push(super::lower_string_from_env_var("output", output));
+            properties.push(super::lower_string_from_env_var("output", output));
         }
 
-        if !&generator.preview_features.is_empty() {
-            let features: Vec<ast::Expression> = generator
-                .preview_features
+        if let Some(ref features) = dbg!(&generator.preview_features) {
+            let features: Vec<ast::Expression> = features
                 .iter()
                 .map(|f| ast::Expression::StringValue(f.to_string(), ast::Span::empty()))
                 .collect::<Vec<ast::Expression>>();
 
-            arguments.push(ast::Argument::new_array("previewFeatures", features));
+            properties.push(dbg!(ast::Argument::new_array("previewFeatures", features)));
         }
 
         let platform_values: Vec<ast::Expression> = generator
             .binary_targets
             .iter()
             .map(|p| lower_string_from_env_var("binaryTargets", p).value)
             .collect();
+
         if !platform_values.is_empty() {
-            arguments.push(ast::Argument::new_array("binaryTargets", platform_values));
+            properties.push(ast::Argument::new_array("binaryTargets", platform_values));
         }
 
         for (key, value) in &generator.config {
-            arguments.push(ast::Argument::new_string(key, value.to_string()));
+            properties.push(ast::Argument::new_string(key, value.to_string()));
         }
 
         ast::GeneratorConfig {
             name: ast::Identifier::new(&generator.name),
-            properties: arguments,
+            properties,
             documentation: generator.documentation.clone().map(|text| ast::Comment { text }),
             span: ast::Span::empty(),
         }

libs/datamodel/core/tests/config/generators.rs

@@ -1,3 +1,5 @@
+use datamodel::Datamodel;
+
 use crate::common::*;
 
 #[test]
@@ -420,3 +422,45 @@ fn empty_preview_features_array_with_empty_space_should_work() {
 
     assert!(config.preview_features().is_empty());
 }
+
+#[test]
+fn empty_preview_features_are_kept_when_rendering() {
+    let schema = indoc! {r#"
+       generator js1 {
+         provider = "a_cat"
+         previewFeatures = []
+       }
+    "#};
+
+    let config = parse_configuration(schema);
+    let rendered = datamodel::render_datamodel_and_config_to_string(&Datamodel::default(), &config);
+
+    let expected = expect![[r#"
+       generator js1 {
+         provider        = "a_cat"
+         previewFeatures = []
+       }
+    "#]];
+
+    expected.assert_eq(&rendered);
+}
+
+#[test]
+fn not_defining_preview_features_should_not_add_them_as_empty_when_rendering() {
+    let schema = indoc! {r#"
+       generator js1 {
+         provider = "a_cat"
+       }
+    "#};
+
+    let config = parse_configuration(schema);
+    let rendered = datamodel::render_datamodel_and_config_to_string(&Datamodel::default(), &config);
+
+    let expected = expect![[r#"
+       generator js1 {
+         provider = "a_cat"
+       }
+    "#]];
+
+    expected.assert_eq(&rendered);
+}