Merge default language data with section language data (#2039)

* Merge language data in config.toml

components/config/src/config/languages.rs

@@ -30,6 +30,91 @@ pub struct LanguageOptions {
     pub translations: HashMap<String, String>,
 }
 
+impl LanguageOptions {
+    /// Merges self with another LanguageOptions, panicking if 2 equivalent fields are not None,
+    /// empty or of default value.
+    pub fn merge(&mut self, other: &LanguageOptions) -> Result<()> {
+        match &self.title {
+            None => self.title = other.title.clone(),
+            Some(self_title) => match &other.title {
+                Some(other_title) => bail!(
+                    "`title` for default language is specified twice, as {:?} and {:?}.",
+                    self_title,
+                    other_title
+                ),
+                None => (),
+            },
+        };
+
+        match &self.description {
+            None => self.description = other.description.clone(),
+            Some(self_description) => match &other.description {
+                Some(other_description) => bail!(
+                    "`description` for default language is specified twice, as {:?} and {:?}.",
+                    self_description,
+                    other_description
+                ),
+                None => (),
+            },
+        };
+
+        self.generate_feed = self.generate_feed || other.generate_feed;
+
+        match &self.feed_filename == "atom.xml" {
+            // "atom.xml" is default value.
+            true => self.feed_filename = other.feed_filename.clone(),
+            false => match &other.feed_filename.is_empty() {
+                false => bail!(
+                    "`feed filename` for default language is specifiec twice, as {:?} and {:?}.",
+                    self.feed_filename,
+                    other.feed_filename
+                ),
+                true => (),
+            },
+        };
+
+        match &self.taxonomies.is_empty() {
+            true => self.taxonomies = other.taxonomies.clone(),
+            false => match &other.taxonomies.is_empty() {
+                false => bail!(
+                    "`taxonomies` for default language is specifiec twice, as {:?} and {:?}.",
+                    self.taxonomies,
+                    other.taxonomies
+                ),
+                true => (),
+            },
+        };
+
+        self.build_search_index = self.build_search_index || other.build_search_index;
+
+        match self.search == search::Search::default() {
+            true => self.search = other.search.clone(),
+            false => match self.search == other.search {
+                false => bail!(
+                    "`search` for default language is specified twice, as {:?} and {:?}.",
+                    self.search,
+                    other.search
+                ),
+                true => (),
+            },
+        };
+
+        match &self.translations.is_empty() {
+            true => self.translations = other.translations.clone(),
+            false => match &other.translations.is_empty() {
+                false => bail!(
+                    "`translations` for default language is specified twice, as {:?} and {:?}.",
+                    self.translations,
+                    other.translations
+                ),
+                true => (),
+            },
+        };
+
+        Ok(())
+    }
+}
+
 /// We want to ensure the language codes are valid ones
 pub fn validate_code(code: &str) -> Result<()> {
     if LanguageIdentifier::from_bytes(code.as_bytes()).is_err() {
@@ -38,3 +123,65 @@ pub fn validate_code(code: &str) -> Result<()> {
 
     Ok(())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn merge_without_conflict() {
+        let mut base_default_language_options = LanguageOptions {
+            title: Some("Site's title".to_string()),
+            description: None,
+            generate_feed: true,
+            feed_filename: "atom.xml".to_string(),
+            taxonomies: vec![],
+            build_search_index: true,
+            search: search::Search::default(),
+            translations: HashMap::new(),
+        };
+
+        let section_default_language_options = LanguageOptions {
+            title: None,
+            description: Some("Site's description".to_string()),
+            generate_feed: false,
+            feed_filename: "rss.xml".to_string(),
+            taxonomies: vec![],
+            build_search_index: true,
+            search: search::Search::default(),
+            translations: HashMap::new(),
+        };
+
+        base_default_language_options.merge(&section_default_language_options).unwrap();
+    }
+
+    #[test]
+    #[should_panic]
+    fn merge_with_conflict() {
+        let mut base_default_language_options = LanguageOptions {
+            title: Some("Site's title".to_string()),
+            description: Some("Duplicate site description".to_string()),
+            generate_feed: true,
+            feed_filename: "".to_string(),
+            taxonomies: vec![],
+            build_search_index: true,
+            search: search::Search::default(),
+            translations: HashMap::new(),
+        };
+
+        let section_default_language_options = LanguageOptions {
+            title: None,
+            description: Some("Site's description".to_string()),
+            generate_feed: false,
+            feed_filename: "Some feed_filename".to_string(),
+            taxonomies: vec![],
+            build_search_index: true,
+            search: search::Search::default(),
+            translations: HashMap::new(),
+        };
+
+        base_default_language_options
+            .merge(&section_default_language_options)
+            .expect("This should lead to panic");
+    }
+}

components/config/src/config/markup.rs

@@ -130,8 +130,11 @@ impl Markdown {
                     )
                 }
             } else {
-                bail!("Highlight theme {} not available.\n\
-                You can load custom themes by configuring `extra_syntaxes_and_themes` to include a list of folders containing '.tmTheme' files", self.highlight_theme)
+                bail!(
+                    "Highlight theme {} not available.\n\
+                You can load custom themes by configuring `extra_syntaxes_and_themes` to include a list of folders containing '.tmTheme' files",
+                    self.highlight_theme
+                )
             }
         }
 
@@ -142,8 +145,11 @@ impl Markdown {
                 // Check extra themes
                 if let Some(extra) = &*self.extra_theme_set {
                     if !extra.themes.contains_key(theme_name) {
-                        bail!("Can't export highlight theme {}, as it does not exist.\n\
-                        Make sure it's spelled correctly, or your custom .tmTheme' is defined properly.", theme_name)
+                        bail!(
+                            "Can't export highlight theme {}, as it does not exist.\n\
+                        Make sure it's spelled correctly, or your custom .tmTheme' is defined properly.",
+                            theme_name
+                        )
                     }
                 }
             }

components/config/src/config/mod.rs

@@ -127,7 +127,7 @@ impl Config {
             languages::validate_code(code)?;
         }
 
-        config.add_default_language();
+        config.add_default_language()?;
         config.slugify_taxonomies();
 
         if !config.ignored_content.is_empty() {
@@ -153,7 +153,7 @@ impl Config {
 
     pub fn default_for_test() -> Self {
         let mut config = Config::default();
-        config.add_default_language();
+        config.add_default_language().unwrap();
         config.slugify_taxonomies();
         config
     }
@@ -206,26 +206,37 @@ impl Config {
         }
     }
 
-    /// Adds the default language to the list of languages if not present
-    pub fn add_default_language(&mut self) {
+    /// Adds the default language to the list of languages if options for it are specified at base level of config.toml.
+    /// If section for the same language also exists, the options at this section and base are merged and then adds it
+    /// to list.
+    pub fn add_default_language(&mut self) -> Result<()> {
         // We automatically insert a language option for the default language *if* it isn't present
         // TODO: what to do if there is like an empty dict for the lang? merge it or use the language
         // TODO: as source of truth?
-        if !self.languages.contains_key(&self.default_language) {
-            self.languages.insert(
-                self.default_language.clone(),
-                languages::LanguageOptions {
-                    title: self.title.clone(),
-                    description: self.description.clone(),
-                    generate_feed: self.generate_feed,
-                    feed_filename: self.feed_filename.clone(),
-                    build_search_index: self.build_search_index,
-                    taxonomies: self.taxonomies.clone(),
-                    search: self.search.clone(),
-                    translations: self.translations.clone(),
-                },
-            );
+
+        let mut base_default_language_options = languages::LanguageOptions {
+            title: self.title.clone(),
+            description: self.description.clone(),
+            generate_feed: self.generate_feed,
+            feed_filename: self.feed_filename.clone(),
+            build_search_index: self.build_search_index,
+            taxonomies: self.taxonomies.clone(),
+            search: self.search.clone(),
+            translations: self.translations.clone(),
+        };
+
+        if let Some(section_default_language_options) = self.languages.get(&self.default_language) {
+            if base_default_language_options != languages::LanguageOptions::default() {
+                println!("Warning: config.toml contains both default language specific information at base and under section `[languages.{}]`, \
+                    which may cause merge conflicts. Please use only one to specify language specific information", self.default_language);
+                base_default_language_options.merge(section_default_language_options)?;
+            } else {
+                return Ok(());
+            }
         }
+        self.languages.insert(self.default_language.clone(), base_default_language_options);
+
+        Ok(())
     }
 
     /// Merges the extra data from the theme with the config extra data
@@ -390,6 +401,74 @@ mod tests {
     use super::*;
     use utils::slugs::SlugifyStrategy;
 
+    #[test]
+    fn can_add_default_language_with_data_only_at_base_section() {
+        let title_base = Some("Base section title".to_string());
+        let description_base = Some("Base section description".to_string());
+
+        let mut config = Config::default();
+        config.title = title_base.clone();
+        config.description = description_base.clone();
+        config.add_default_language().unwrap();
+
+        let default_language_options =
+            config.languages.get(&config.default_language).unwrap().clone();
+        assert_eq!(default_language_options.title, title_base);
+        assert_eq!(default_language_options.description, description_base);
+    }
+
+    #[test]
+    fn can_add_default_language_with_data_at_base_and_language_section() {
+        let title_base = Some("Base section title".to_string());
+        let description_lang_section = Some("Language section description".to_string());
+
+        let mut config = Config::default();
+        config.title = title_base.clone();
+        config.languages.insert(
+            config.default_language.clone(),
+            languages::LanguageOptions {
+                title: None,
+                description: description_lang_section.clone(),
+                generate_feed: true,
+                feed_filename: config.feed_filename.clone(),
+                taxonomies: config.taxonomies.clone(),
+                build_search_index: false,
+                search: search::Search::default(),
+                translations: config.translations.clone(),
+            },
+        );
+        config.add_default_language().unwrap();
+
+        let default_language_options =
+            config.languages.get(&config.default_language).unwrap().clone();
+        assert_eq!(default_language_options.title, title_base);
+        assert_eq!(default_language_options.description, description_lang_section);
+    }
+
+    #[test]
+    fn errors_when_same_field_present_at_base_and_language_section() {
+        let title_base = Some("Base section title".to_string());
+        let title_lang_section = Some("Language section title".to_string());
+
+        let mut config = Config::default();
+        config.title = title_base.clone();
+        config.languages.insert(
+            config.default_language.clone(),
+            languages::LanguageOptions {
+                title: title_lang_section.clone(),
+                description: None,
+                generate_feed: true,
+                feed_filename: config.feed_filename.clone(),
+                taxonomies: config.taxonomies.clone(),
+                build_search_index: false,
+                search: search::Search::default(),
+                translations: config.translations.clone(),
+            },
+        );
+        let result = config.add_default_language();
+        assert!(result.is_err());
+    }
+
     #[test]
     fn can_import_valid_config() {
         let config = r#"