feat(linter/plugins): RuleTester test fixes

apps/oxlint/src-js/bindings.d.ts

@@ -26,6 +26,20 @@ export declare const enum Severity {
   Warning = 'Warning',
   Advice = 'Advice'
 }
+/**
+ * Apply fixes to source text and return the fixed code.
+ *
+ * - `source_text` is the original source code.
+ * - `fixes_json` is a JSON string containing `Vec<Vec<JsFix>>` — an array of fix groups,
+ *    one group per diagnostic which provides fixes.
+ *    Each inner array should have length of 1 at minimum.
+ *
+ * Each group's fixes are merged, then all merged fixes are applied to `source_text`.
+ *
+ * Fix ranges are converted from UTF-16 code units to UTF-8 bytes.
+ */
+export declare function applyFixes(sourceText: string, fixesJson: string): string | null
+
 /**
  * Get offset within a `Uint8Array` which is aligned on `BUFFER_ALIGN`.
  *

apps/oxlint/src-js/bindings.js

@@ -579,8 +579,9 @@ if (!nativeBinding) {
   throw new Error(`Failed to load native binding`)
 }
 
-const { Severity, getBufferOffset, lint, parseRawSync, rawTransferSupported } = nativeBinding
+const { Severity, applyFixes, getBufferOffset, lint, parseRawSync, rawTransferSupported } = nativeBinding
 export { Severity }
+export { applyFixes }
 export { getBufferOffset }
 export { lint }
 export { parseRawSync }

apps/oxlint/src-js/package/rule_tester.ts

@@ -11,6 +11,7 @@ import { default as assert, AssertionError } from "node:assert";
 import { join as pathJoin, isAbsolute as isAbsolutePath, dirname } from "node:path";
 import util from "node:util";
 import stableJsonStringify from "json-stable-stringify-without-jsonify";
+import { applyFixes } from "../bindings.js";
 import { ecmaFeaturesOverride, setEcmaVersion, ECMA_VERSION } from "../plugins/context.ts";
 import { registerPlugin, registeredRules } from "../plugins/load.ts";
 import { lintFileImpl, resetStateAfterError } from "../plugins/lint.ts";
@@ -20,6 +21,7 @@ import { diagnostics, replacePlaceholders, PLACEHOLDER_REGEX } from "../plugins/
 import { parse } from "./parse.ts";
 
 import type { RequireAtLeastOne } from "type-fest";
+import type { FixReport } from "../plugins/fix.ts";
 import type { Plugin, Rule } from "../plugins/load.ts";
 import type { Options } from "../plugins/options.ts";
 import type { DiagnosticData, Suggestion } from "../plugins/report.ts";
@@ -347,6 +349,7 @@ interface Diagnostic {
   column: number;
   endLine: number;
   endColumn: number;
+  fixes: FixReport[] | null;
   suggestions: Suggestion[] | null;
 }
 
@@ -621,7 +624,37 @@ function assertInvalidTestCasePasses(test: InvalidTestCase, plugin: Plugin, conf
     }
   }
 
-  // TODO: Test output after fixes
+  // Test output after fixes
+  const fixGroups: FixReport[][] = [];
+  for (const diagnostic of diagnostics) {
+    if (diagnostic.fixes !== null) fixGroups.push(diagnostic.fixes);
+  }
+
+  const { code } = test;
+
+  let fixedCode;
+  if (fixGroups.length > 0) {
+    fixedCode = applyFixes(code, JSON.stringify(fixGroups));
+    if (fixedCode === null) throw new Error("Failed to apply fixes");
+  } else {
+    fixedCode = code;
+  }
+
+  if (Object.hasOwn(test, "output")) {
+    const expectedOutput = test.output;
+    if (expectedOutput === null) {
+      assert.strictEqual(fixedCode, code, "Expected no autofixes to be suggested");
+    } else {
+      assert.strictEqual(fixedCode, expectedOutput, "Output is incorrect");
+      assert.notStrictEqual(
+        code,
+        expectedOutput,
+        "Test property `output` matches `code`. If no autofix is expected, set output to `null`.",
+      );
+    }
+  } else {
+    assert.strictEqual(fixedCode, code, "The rule fixed the code. Please add `output` property.");
+  }
 }
 
 /**
@@ -1068,6 +1101,7 @@ function lint(test: TestCase, plugin: Plugin): Diagnostic[] {
         column,
         endLine,
         endColumn,
+        fixes: diagnostic.fixes,
         suggestions: null, // TODO
       };
     });

apps/oxlint/src/js_plugins/fix.rs

@@ -0,0 +1,40 @@
+use napi_derive::napi;
+
+use oxc_ast_visit::utf8_to_utf16::Utf8ToUtf16;
+use oxc_diagnostics::OxcDiagnostic;
+use oxc_linter::{Fixer, JsFix, Message, PossibleFixes, convert_and_merge_js_fixes};
+
+/// Apply fixes to source text and return the fixed code.
+///
+/// - `source_text` is the original source code.
+/// - `fixes_json` is a JSON string containing `Vec<Vec<JsFix>>` — an array of fix groups,
+///    one group per diagnostic which provides fixes.
+///    Each inner array should have length of 1 at minimum.
+///
+/// Each group's fixes are merged, then all merged fixes are applied to `source_text`.
+///
+/// Fix ranges are converted from UTF-16 code units to UTF-8 bytes.
+#[napi]
+#[allow(dead_code, clippy::needless_pass_by_value, clippy::allow_attributes)]
+pub fn apply_fixes(source_text: String, fixes_json: String) -> Option<String> {
+    // Deserialize fixes JSON
+    let fix_groups: Vec<Vec<JsFix>> = serde_json::from_str(&fixes_json).ok()?;
+
+    // Create `Utf8ToUtf16` converter
+    let span_converter = Utf8ToUtf16::new(&source_text);
+
+    // Merge fix groups into a single fix per group
+    let messages = fix_groups
+        .into_iter()
+        .map(|group| {
+            convert_and_merge_js_fixes(group, &source_text, &span_converter)
+                .ok()
+                .map(|fix| Message::new(OxcDiagnostic::error(""), PossibleFixes::Single(fix)))
+        })
+        .collect::<Option<Vec<_>>>()?;
+
+    // Apply all the fixes
+    let fixed_code = Fixer::new(&source_text, messages, None).fix().fixed_code.into_owned();
+
+    Some(fixed_code)
+}

apps/oxlint/src/js_plugins/mod.rs

@@ -1,5 +1,8 @@
 mod external_linter;
 
+#[cfg(all(target_pointer_width = "64", target_endian = "little"))]
+pub mod fix;
+
 #[cfg(all(target_pointer_width = "64", target_endian = "little"))]
 pub mod parse;