feat: Cache JSON file loads

changelog.d/20250915_144507_markiewicz_cache_json.md

@@ -0,0 +1,47 @@
+<!--
+A new scriv changelog fragment.
+
+Uncomment the section that is right (remove the HTML comment wrapper).
+For top level release notes, leave all the headers commented out.
+-->
+
+<!--
+### Added
+
+- A bullet item for the Added category.
+
+-->
+### Changed
+
+- Parsed JSON files are now cached to reduce I/O and parsing costs.
+
+<!--
+### Fixed
+
+- A bullet item for the Fixed category.
+
+-->
+<!--
+### Deprecated
+
+- A bullet item for the Deprecated category.
+
+-->
+<!--
+### Removed
+
+- A bullet item for the Removed category.
+
+-->
+<!--
+### Security
+
+- A bullet item for the Security category.
+
+-->
+<!--
+### Infrastructure
+
+- A bullet item for the Infrastructure category.
+
+-->

src/files/json.test.ts

@@ -3,6 +3,7 @@ import type { BIDSFile } from '../types/filetree.ts'
 import type { FileIgnoreRules } from './ignore.ts'
 import { testAsyncFileAccess } from './access.test.ts'
 
+import { pathsToTree } from '../files/filetree.ts'
 import { loadJSON } from './json.ts'
 
 function encodeUTF16(text: string) {
@@ -18,9 +19,12 @@ function encodeUTF16(text: string) {
   return buffer
 }
 
-function makeFile(text: string, encoding: string): BIDSFile {
+function makeFile(path: string, text: string, encoding: string): BIDSFile {
   const bytes = encoding === 'utf-8' ? new TextEncoder().encode(text) : encodeUTF16(text)
+  const file = pathsToTree([path]).get(path) as BIDSFile
   return {
+    path: file.path,
+    parent: file.parent,
     readBytes: async (size: number) => {
       return new Uint8Array(bytes)
     },
@@ -30,13 +34,13 @@ function makeFile(text: string, encoding: string): BIDSFile {
 
 Deno.test('Test JSON error conditions', async (t) => {
   await t.step('Load valid JSON', async () => {
-    const JSONfile = makeFile('{"a": 1}', 'utf-8')
+    const JSONfile = makeFile('/valid-contents.json', '{"a": 1}', 'utf-8')
     const result = await loadJSON(JSONfile)
     assertObjectMatch(result, { a: 1 })
   })
 
   await t.step('Error on BOM', async () => {
-    const BOMfile = makeFile('\uFEFF{"a": 1}', 'utf-8')
+    const BOMfile = makeFile('/BOM.json', '\uFEFF{"a": 1}', 'utf-8')
     let error: any = undefined
     await loadJSON(BOMfile).catch((e) => {
       error = e
@@ -45,7 +49,7 @@ Deno.test('Test JSON error conditions', async (t) => {
   })
 
   await t.step('Error on UTF-16', async () => {
-    const UTF16file = makeFile('{"a": 1}', 'utf-16')
+    const UTF16file = makeFile('/utf16.json', '{"a": 1}', 'utf-16')
     let error: any = undefined
     await loadJSON(UTF16file).catch((e) => {
       error = e
@@ -54,13 +58,14 @@ Deno.test('Test JSON error conditions', async (t) => {
   })
 
   await t.step('Error on invalid JSON syntax', async () => {
-    const badJSON = makeFile('{"a": 1]', 'utf-8')
+    const badJSON = makeFile('/bad-syntax.json', '{"a": 1]', 'utf-8')
     let error: any = undefined
     await loadJSON(badJSON).catch((e) => {
       error = e
     })
     assertObjectMatch(error, { code: 'JSON_INVALID' })
   })
+  loadJSON.cache.clear()
 })
 
 testAsyncFileAccess('Test file access errors for loadJSON', loadJSON)

src/files/json.ts

@@ -1,3 +1,4 @@
+import { filememoizeAsync } from '../utils/memoize.ts'
 import type { BIDSFile } from '../types/filetree.ts'
 import { readBytes } from './access.ts'
 
@@ -21,7 +22,7 @@ async function readJSONText(file: BIDSFile): Promise<string> {
   }
 }
 
-export async function loadJSON(file: BIDSFile): Promise<Record<string, unknown>> {
+async function _loadJSON(file: BIDSFile): Promise<Record<string, unknown>> {
   const text = await readJSONText(file) // Raise encoding errors
   let parsedText
   try {
@@ -37,3 +38,5 @@ export async function loadJSON(file: BIDSFile): Promise<Record<string, unknown>>
   }
   return parsedText
 }
+
+export const loadJSON = filememoizeAsync(_loadJSON)

src/schema/walk.ts

@@ -2,6 +2,7 @@ import { BIDSContext, type BIDSContextDataset } from './context.ts'
 import type { BIDSFile, FileTree } from '../types/filetree.ts'
 import type { DatasetIssues } from '../issues/datasetIssues.ts'
 import { loadTSV } from '../files/tsv.ts'
+import { loadJSON } from '../files/json.ts'
 
 function* quickWalk(dir: FileTree): Generator<BIDSFile> {
   for (const file of dir.files) {
@@ -49,6 +50,7 @@ async function* _walkFileTree(
     }
   }
   loadTSV.cache.delete(fileTree.path)
+  loadJSON.cache.delete(fileTree.path)
 }
 
 /** Walk all files in the dataset and construct a context for each one */