feat: make configuration items null-safe (#1988)

When passing configuration items with null values, the default
configurations are used. Note: I don't ensure this to be always true,
some configuration items may have different non-default behaviors when
accepting a null value now or in future. The `deserialize_null_default`
is taken from https://github.com/serde-rs/serde/issues/1098.

Configuration parsing changes:
+ some configurations only accepting boolean now coerce null to `false`
(default).
+ some configurations only accepting an object now coerce null to
default.
+ The `tinymist.preview.invertColors` now now coerces null to `"never"`
(default).

crates/tinymist-query/src/analysis/completion.rs

@@ -70,17 +70,17 @@ type LspCompletion = CompletionItem;
 #[serde(rename_all = "camelCase")]
 pub struct CompletionFeat {
     /// Whether to trigger completions on arguments (placeholders) of snippets.
-    #[serde(default)]
+    #[serde(default, deserialize_with = "deserialize_null_default")]
     pub trigger_on_snippet_placeholders: bool,
     /// Whether supports trigger suggest completion, a.k.a. auto-completion.
-    #[serde(default)]
+    #[serde(default, deserialize_with = "deserialize_null_default")]
     pub trigger_suggest: bool,
     /// Whether supports trigger parameter hint, a.k.a. signature help.
-    #[serde(default)]
+    #[serde(default, deserialize_with = "deserialize_null_default")]
     pub trigger_parameter_hints: bool,
     /// Whether supports trigger the command combining suggest and parameter
     /// hints.
-    #[serde(default)]
+    #[serde(default, deserialize_with = "deserialize_null_default")]
     pub trigger_suggest_and_parameter_hints: bool,
 
     /// The Way to complete symbols.
@@ -995,6 +995,17 @@ fn is_arg_like_context(mut matching: &LinkedNode) -> bool {
 //     ctx.completions.push(compl);
 // }
 
+fn deserialize_null_default<'de, D, T>(deserializer: D) -> Result<T, D::Error>
+where
+    T: Default + Deserialize<'de>,
+    D: serde::Deserializer<'de>,
+{
+    let opt = Option::deserialize(deserializer)?;
+    Ok(opt.unwrap_or_default())
+}
+
+// todo: doesn't complete parameter now, which is not good.
+
 #[cfg(test)]
 mod tests {
     use super::slice_at;
@@ -1009,5 +1020,3 @@ mod tests {
         }
     }
 }
-
-// todo: doesn't complete parameter now, which is not good.

crates/tinymist/src/config.rs

@@ -862,19 +862,19 @@ pub enum SemanticTokensMode {
 #[serde(rename_all = "camelCase")]
 pub struct PreviewFeat {
     /// The browsing preview options.
-    #[serde(default)]
+    #[serde(default, deserialize_with = "deserialize_null_default")]
     pub browsing: BrowsingPreviewOpts,
     /// The background preview options.
-    #[serde(default)]
+    #[serde(default, deserialize_with = "deserialize_null_default")]
     pub background: BackgroundPreviewOpts,
     /// When to refresh the preview.
     #[serde(default)]
     pub refresh: Option<TaskWhen>,
     /// Whether to enable partial rendering.
-    #[serde(default)]
+    #[serde(default, deserialize_with = "deserialize_null_default")]
     pub partial_rendering: bool,
     /// Invert colors for the preview.
-    #[serde(default)]
+    #[serde(default, deserialize_with = "deserialize_null_default")]
     pub invert_colors: PreviewInvertColors,
 }
 
@@ -911,6 +911,7 @@ pub struct BrowsingPreviewOpts {
 #[serde(rename_all = "camelCase")]
 pub struct BackgroundPreviewOpts {
     /// Whether to run the preview in the background.
+    #[serde(default, deserialize_with = "deserialize_null_default")]
     pub enabled: bool,
     /// The arguments for the background preview.
     pub args: Option<Vec<String>>,
@@ -957,6 +958,15 @@ pub(crate) fn get_semantic_tokens_options() -> SemanticTokensOptions {
     }
 }
 
+fn deserialize_null_default<'de, D, T>(deserializer: D) -> Result<T, D::Error>
+where
+    T: Default + Deserialize<'de>,
+    D: serde::Deserializer<'de>,
+{
+    let opt = Option::deserialize(deserializer)?;
+    Ok(opt.unwrap_or_default())
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -1106,33 +1116,69 @@ mod tests {
     }
 
     #[test]
-    fn test_null_completion() {
+    fn test_null_args() {
-        let mut config = Config::default();
+        fn test_good_config(path: &str) -> Config {
-        let update = json!({
+            let mut obj = json!(null);
-            "completion": null
+            let path = path.split('.').collect::<Vec<_>>();
-        });
+            for p in path.iter().rev() {
-
+                obj = json!({ *p: obj });
-        good_config(&mut config, &update);
             }
 
-    #[test]
+            let mut c = Config::default();
-    fn test_null_root() {
+            good_config(&mut c, &obj);
-        let mut config = Config::default();
+            c
-        let update = json!({
-            "root": null
-        });
-
-        good_config(&mut config, &update);
         }
 
-    #[test]
+        test_good_config("root");
-    fn test_null_extra_args() {
+        test_good_config("rootPath");
-        let mut config = Config::default();
+        test_good_config("colorTheme");
-        let update = json!({
+        test_good_config("lint");
-            "typstExtraArgs": null
+        test_good_config("customizedShowDocument");
-        });
+        test_good_config("projectResolution");
+        test_good_config("exportPdf");
+        test_good_config("exportTarget");
+        test_good_config("fontPaths");
+        test_good_config("formatterMode");
+        test_good_config("formatterPrintWidth");
+        test_good_config("formatterIndentSize");
+        test_good_config("formatterProseWrap");
+        test_good_config("outputPath");
+        test_good_config("semanticTokens");
+        test_good_config("delegateFsRequests");
+        test_good_config("supportHtmlInMarkdown");
+        test_good_config("supportExtendedCodeAction");
+        test_good_config("development");
+        test_good_config("systemFonts");
 
-        good_config(&mut config, &update);
+        test_good_config("completion");
+        test_good_config("completion.triggerSuggest");
+        test_good_config("completion.triggerParameterHints");
+        test_good_config("completion.triggerSuggestAndParameterHints");
+        test_good_config("completion.triggerOnSnippetPlaceholders");
+        test_good_config("completion.symbol");
+        test_good_config("completion.postfix");
+        test_good_config("completion.postfixUfcs");
+        test_good_config("completion.postfixUfcsLeft");
+        test_good_config("completion.postfixUfcsRight");
+        test_good_config("completion.postfixSnippets");
+
+        test_good_config("lint");
+        test_good_config("lint.enabled");
+        test_good_config("lint.when");
+
+        test_good_config("preview");
+        test_good_config("preview.browsing");
+        test_good_config("preview.browsing.args");
+        test_good_config("preview.background");
+        test_good_config("preview.background.enabled");
+        test_good_config("preview.background.args");
+        test_good_config("preview.refresh");
+        test_good_config("preview.partialRendering");
+        let c = test_good_config("preview.invertColors");
+        assert_eq!(
+            c.preview.invert_colors,
+            PreviewInvertColors::Enum(PreviewInvertColor::Never)
+        );
     }
 
     #[test]