fix(oxfmt): Support .editorconfig tab_width fallback

apps/oxfmt/src-js/config.generated.ts

@@ -197,7 +197,7 @@ export interface Oxfmtrc {
    * Specify the number of spaces per indentation-level.
    *
    * - Default: `2`
-   * - Overrides `.editorconfig.indent_size`
+   * - Overrides `.editorconfig.indent_size` (falls back to `.editorconfig.tab_width`)
    */
   tabWidth?: number;
   /**
@@ -474,7 +474,7 @@ export interface FormatConfig {
    * Specify the number of spaces per indentation-level.
    *
    * - Default: `2`
-   * - Overrides `.editorconfig.indent_size`
+   * - Overrides `.editorconfig.indent_size` (falls back to `.editorconfig.tab_width`)
    */
   tabWidth?: number;
   /**

apps/oxfmt/src/core/config.rs

@@ -611,6 +611,7 @@ fn load_editorconfig(
 /// - end_of_line
 /// - indent_style
 /// - indent_size
+/// - tab_width
 /// - insert_final_newline
 fn has_editorconfig_overrides(editorconfig: &EditorConfig, path: &Path) -> bool {
     let sections = editorconfig.sections();
@@ -632,6 +633,7 @@ fn has_editorconfig_overrides(editorconfig: &EditorConfig, path: &Path) -> bool
                 || resolved.end_of_line != root.end_of_line
                 || resolved.indent_style != root.indent_style
                 || resolved.indent_size != root.indent_size
+                || resolved.tab_width != root.tab_width
                 || resolved.insert_final_newline != root.insert_final_newline
         }
         // No `[*]` section means any resolved property is an override
@@ -640,6 +642,7 @@ fn has_editorconfig_overrides(editorconfig: &EditorConfig, path: &Path) -> bool
                 || resolved.end_of_line != EditorConfigProperty::Unset
                 || resolved.indent_style != EditorConfigProperty::Unset
                 || resolved.indent_size != EditorConfigProperty::Unset
+                || resolved.tab_width != EditorConfigProperty::Unset
                 || resolved.insert_final_newline != EditorConfigProperty::Unset
         }
     }
@@ -676,11 +679,17 @@ fn apply_editorconfig(config: &mut FormatConfig, props: &EditorConfigProperties)
         });
     }
 
-    #[expect(clippy::cast_possible_truncation)]
-    if config.tab_width.is_none()
-        && let EditorConfigProperty::Value(size) = props.indent_size
-    {
-        config.tab_width = Some(size as u8);
+    if config.tab_width.is_none() {
+        // Match Prettier's behavior: Only use `indent_size` when `useTabs: false`.
+        // https://github.com/prettier/prettier/blob/90983f40dce5e20beea4e5618b5e0426a6a7f4f0/src/config/editorconfig/editorconfig-to-prettier.js#L25-L30
+        #[expect(clippy::cast_possible_truncation)]
+        if config.use_tabs == Some(false)
+            && let EditorConfigProperty::Value(size) = props.indent_size
+        {
+            config.tab_width = Some(size as u8);
+        } else if let EditorConfigProperty::Value(size) = props.tab_width {
+            config.tab_width = Some(size as u8);
+        }
     }
 
     if config.insert_final_newline.is_none()

apps/oxfmt/src/core/oxfmtrc/format_config.rs

@@ -63,7 +63,7 @@ pub struct FormatConfig {
     /// Specify the number of spaces per indentation-level.
     ///
     /// - Default: `2`
-    /// - Overrides `.editorconfig.indent_size`
+    /// - Overrides `.editorconfig.indent_size` (falls back to `.editorconfig.tab_width`)
     #[serde(skip_serializing_if = "Option::is_none")]
     pub tab_width: Option<u8>,
     /// Which end of line characters to apply.

apps/oxfmt/test/cli/editorconfig/__snapshots__/editorconfig.test.ts.snap

@@ -153,3 +153,17 @@ nested/deep/test.json
 
 --------------------"
 `;
+
+exports[`editorconfig > tab_width fallback when indent_size is not set 1`] = `
+"--- FILE -----------
+test.js
+--- BEFORE ---------
+if (condition) { console.log("hello world"); }
+
+--- AFTER ----------
+if (condition) {
+        console.log("hello world");
+}
+
+--------------------"
+`;

apps/oxfmt/test/cli/editorconfig/editorconfig.test.ts

@@ -78,6 +78,18 @@ describe("editorconfig", () => {
     expect(snapshot).toMatchSnapshot();
   });
 
+  // .editorconfig:
+  //   [*] indent_style=space, tab_width=8
+  //   (no indent_size)
+  //
+  // Expected: useTabs=false, tabWidth=8 (tab_width used as fallback for indent_size)
+  // - Indentation should use 8 spaces
+  it("tab_width fallback when indent_size is not set", async () => {
+    const cwd = join(fixturesDir, "tab_width_fallback");
+    const snapshot = await runWriteModeAndSnapshot(cwd, ["test.js"]);
+    expect(snapshot).toMatchSnapshot();
+  });
+
   // .editorconfig: (empty file)
   //
   // Expected: default settings (useTabs=false, tabWidth=2)

apps/oxfmt/test/cli/editorconfig/fixtures/tab_width_fallback/.editorconfig

@@ -0,0 +1,3 @@
+[*]
+indent_style = space
+tab_width = 8

apps/oxfmt/test/cli/editorconfig/fixtures/tab_width_fallback/test.js

@@ -0,0 +1 @@
+if (condition) { console.log("hello world"); }

npm/oxfmt/configuration_schema.json

@@ -162,11 +162,11 @@
       "markdownDescription": "Sort Tailwind CSS classes.\n\nUsing the same algorithm as [prettier-plugin-tailwindcss](https://github.com/tailwindlabs/prettier-plugin-tailwindcss).\nOption names omit the `tailwind` prefix used in the original plugin (e.g., `config` instead of `tailwindConfig`).\nFor details, see each field's documentation.\n\nPass `true` or an object to enable with defaults, or omit/set `false` to disable.\n\n- Default: Disabled"
     },
     "tabWidth": {
-      "description": "Specify the number of spaces per indentation-level.\n\n- Default: `2`\n- Overrides `.editorconfig.indent_size`",
+      "description": "Specify the number of spaces per indentation-level.\n\n- Default: `2`\n- Overrides `.editorconfig.indent_size` (falls back to `.editorconfig.tab_width`)",
       "type": "integer",
       "format": "uint8",
       "minimum": 0.0,
-      "markdownDescription": "Specify the number of spaces per indentation-level.\n\n- Default: `2`\n- Overrides `.editorconfig.indent_size`"
+      "markdownDescription": "Specify the number of spaces per indentation-level.\n\n- Default: `2`\n- Overrides `.editorconfig.indent_size` (falls back to `.editorconfig.tab_width`)"
     },
     "trailingComma": {
       "description": "Print trailing commas wherever possible in multi-line comma-separated syntactic structures.\n\nA single-line array, for example, never gets trailing commas.\n\n- Default: `\"all\"`",
@@ -391,11 +391,11 @@
           "markdownDescription": "Sort Tailwind CSS classes.\n\nUsing the same algorithm as [prettier-plugin-tailwindcss](https://github.com/tailwindlabs/prettier-plugin-tailwindcss).\nOption names omit the `tailwind` prefix used in the original plugin (e.g., `config` instead of `tailwindConfig`).\nFor details, see each field's documentation.\n\nPass `true` or an object to enable with defaults, or omit/set `false` to disable.\n\n- Default: Disabled"
         },
         "tabWidth": {
-          "description": "Specify the number of spaces per indentation-level.\n\n- Default: `2`\n- Overrides `.editorconfig.indent_size`",
+          "description": "Specify the number of spaces per indentation-level.\n\n- Default: `2`\n- Overrides `.editorconfig.indent_size` (falls back to `.editorconfig.tab_width`)",
           "type": "integer",
           "format": "uint8",
           "minimum": 0.0,
-          "markdownDescription": "Specify the number of spaces per indentation-level.\n\n- Default: `2`\n- Overrides `.editorconfig.indent_size`"
+          "markdownDescription": "Specify the number of spaces per indentation-level.\n\n- Default: `2`\n- Overrides `.editorconfig.indent_size` (falls back to `.editorconfig.tab_width`)"
         },
         "trailingComma": {
           "description": "Print trailing commas wherever possible in multi-line comma-separated syntactic structures.\n\nA single-line array, for example, never gets trailing commas.\n\n- Default: `\"all\"`",

tasks/website_formatter/src/snapshots/schema_json.snap

@@ -166,11 +166,11 @@ expression: json
       "markdownDescription": "Sort Tailwind CSS classes.\n\nUsing the same algorithm as [prettier-plugin-tailwindcss](https://github.com/tailwindlabs/prettier-plugin-tailwindcss).\nOption names omit the `tailwind` prefix used in the original plugin (e.g., `config` instead of `tailwindConfig`).\nFor details, see each field's documentation.\n\nPass `true` or an object to enable with defaults, or omit/set `false` to disable.\n\n- Default: Disabled"
     },
     "tabWidth": {
-      "description": "Specify the number of spaces per indentation-level.\n\n- Default: `2`\n- Overrides `.editorconfig.indent_size`",
+      "description": "Specify the number of spaces per indentation-level.\n\n- Default: `2`\n- Overrides `.editorconfig.indent_size` (falls back to `.editorconfig.tab_width`)",
       "type": "integer",
       "format": "uint8",
       "minimum": 0.0,
-      "markdownDescription": "Specify the number of spaces per indentation-level.\n\n- Default: `2`\n- Overrides `.editorconfig.indent_size`"
+      "markdownDescription": "Specify the number of spaces per indentation-level.\n\n- Default: `2`\n- Overrides `.editorconfig.indent_size` (falls back to `.editorconfig.tab_width`)"
     },
     "trailingComma": {
       "description": "Print trailing commas wherever possible in multi-line comma-separated syntactic structures.\n\nA single-line array, for example, never gets trailing commas.\n\n- Default: `\"all\"`",
@@ -395,11 +395,11 @@ expression: json
           "markdownDescription": "Sort Tailwind CSS classes.\n\nUsing the same algorithm as [prettier-plugin-tailwindcss](https://github.com/tailwindlabs/prettier-plugin-tailwindcss).\nOption names omit the `tailwind` prefix used in the original plugin (e.g., `config` instead of `tailwindConfig`).\nFor details, see each field's documentation.\n\nPass `true` or an object to enable with defaults, or omit/set `false` to disable.\n\n- Default: Disabled"
         },
         "tabWidth": {
-          "description": "Specify the number of spaces per indentation-level.\n\n- Default: `2`\n- Overrides `.editorconfig.indent_size`",
+          "description": "Specify the number of spaces per indentation-level.\n\n- Default: `2`\n- Overrides `.editorconfig.indent_size` (falls back to `.editorconfig.tab_width`)",
           "type": "integer",
           "format": "uint8",
           "minimum": 0.0,
-          "markdownDescription": "Specify the number of spaces per indentation-level.\n\n- Default: `2`\n- Overrides `.editorconfig.indent_size`"
+          "markdownDescription": "Specify the number of spaces per indentation-level.\n\n- Default: `2`\n- Overrides `.editorconfig.indent_size` (falls back to `.editorconfig.tab_width`)"
         },
         "trailingComma": {
           "description": "Print trailing commas wherever possible in multi-line comma-separated syntactic structures.\n\nA single-line array, for example, never gets trailing commas.\n\n- Default: `\"all\"`",

tasks/website_formatter/src/snapshots/schema_markdown.snap

@@ -970,7 +970,7 @@ type: `integer`
 Specify the number of spaces per indentation-level.
 
 - Default: `2`
-- Overrides `.editorconfig.indent_size`
+- Overrides `.editorconfig.indent_size` (falls back to `.editorconfig.tab_width`)
 
 
 ##### overrides[n].options.trailingComma
@@ -1443,7 +1443,7 @@ type: `integer`
 Specify the number of spaces per indentation-level.
 
 - Default: `2`
-- Overrides `.editorconfig.indent_size`
+- Overrides `.editorconfig.indent_size` (falls back to `.editorconfig.tab_width`)
 
 
 ## trailingComma