refactor(linter/plugins): share ast between files (#14349)

Pure refactor. Remove `getAst` getter function, and share `ast` directly between files with `import` / `export`.

Author: overlookmotel

apps/oxlint/src-js/plugins/lint.ts

@@ -1,6 +1,6 @@
 import { diagnostics, setupContextForFile } from './context.js';
 import { registeredRules } from './load.js';
-import { getAst, resetSource, setupSourceForFile } from './source_code.js';
+import { ast, initAst, resetSource, setupSourceForFile } from './source_code.js';
 import { assertIs, getErrorMessage } from './utils.js';
 import { addVisitorToCompiled, compiledVisitor, finalizeCompiledVisitor, initCompiledVisitor } from './visitor.js';
 
@@ -134,8 +134,8 @@ function lintFileImpl(filePath: string, bufferId: number, buffer: Uint8Array | n
   // Some rules seen in the wild return an empty visitor object from `create` if some initial check fails
   // e.g. file extension is not one the rule acts on.
   if (needsVisit) {
-    const program = getAst();
-    walkProgram(program, compiledVisitor);
+    if (ast === null) initAst();
+    walkProgram(ast, compiledVisitor);
 
     // Lazy implementation
     /*

apps/oxlint/src-js/plugins/source_code.ts

@@ -30,10 +30,10 @@ let buffer: BufferWithArrays | null = null;
 let hasBOM = false;
 
 // Lazily populated when `SOURCE_CODE.text` or `SOURCE_CODE.ast` is accessed,
-// or `getAst()` is called before the AST is walked.
+// or `initAst()` is called before the AST is walked.
 let sourceText: string | null = null;
 let sourceByteLen: number = 0;
-let ast: Program | null = null;
+export let ast: Program | null = null;
 
 // Lazily populated when `SOURCE_CODE.lines` is accessed.
 // `lineStartOffsets` starts as `[0]`, and `resetSource` doesn't remove that initial element, so it's never empty.
@@ -66,21 +66,11 @@ function initSourceText(): void {
 /**
  * Deserialize AST from buffer.
  */
-function initAst(): void {
+export function initAst(): void {
   if (sourceText === null) initSourceText();
   ast = deserializeProgramOnly(buffer, sourceText, sourceByteLen);
 }
 
-/**
- * Get AST of the file being linted.
- * If AST has not already been deserialized, do it now.
- * @returns AST of the file being linted.
- */
-export function getAst(): Program {
-  if (ast === null) initAst();
-  return ast;
-}
-
 /**
  * Split source text into lines.
  */
@@ -151,7 +141,8 @@ export const SOURCE_CODE = Object.freeze({
 
   // Get AST of the file.
   get ast(): Program {
-    return getAst();
+    if (ast === null) initAst();
+    return ast;
   },
 
   // Get `ScopeManager` for the file.