fix: catch json parse error in fetchTokenList (#6278)

* fix: catch json parse error in fetchTokenList

* fix: refactor fetchTokenList and add more tests

* fix: import in test

* fix: comments and names

* fix: comment format

* fix: comment formatting

src/lib/hooks/useTokenList/fetchTokenList.test.ts

@@ -18,7 +18,9 @@ describe('fetchTokenList', () => {
     fetch.mockOnceIf(url, () => {
       throw new Error()
     })
-    await expect(fetchTokenList(url, resolver)).rejects.toThrow(`failed to fetch list: ${url}`)
+    await expect(fetchTokenList(url, resolver)).rejects.toThrow(
+      `No valid token list found at any URLs derived from ${url}.`
+    )
     expect(console.debug).toHaveBeenCalled()
     expect(resolver).not.toHaveBeenCalled()
   })
@@ -33,9 +35,63 @@ describe('fetchTokenList', () => {
     expect(resolver).toHaveBeenCalledWith(url)
   })
 
+  it('throws an error when the ENS resolver throws', async () => {
+    const url = 'example.eth'
+    const error = new Error('ENS resolver error')
+    resolver.mockRejectedValue(error)
+    await expect(fetchTokenList(url, resolver)).rejects.toThrow(`failed to resolve ENS name: ${url}`)
+    expect(resolver).toHaveBeenCalledWith(url)
+  })
+
+  it('fetches and validates a list from an ENS address', async () => {
+    jest.mock('../../utils/contenthashToUri', () =>
+      jest.fn().mockImplementation(() => 'ipfs://QmPgEqyV3m8SB52BS2j2mJpu9zGprhj2BGCHtRiiw2fdM1')
+    )
+    const url = 'example.eth'
+    const contenthash = '0xe3010170122013e051d1cfff20606de36845d4fe28deb9861a319a5bc8596fa4e610e8803918'
+    const translatedUri = 'https://cloudflare-ipfs.com/ipfs/QmPgEqyV3m8SB52BS2j2mJpu9zGprhj2BGCHtRiiw2fdM1/'
+    resolver.mockResolvedValue(contenthash)
+    fetch.mockOnceIf(translatedUri, () => Promise.resolve(JSON.stringify(defaultTokenList)))
+    await expect(fetchTokenList(url, resolver)).resolves.toStrictEqual(defaultTokenList)
+  })
+
+  it('throws for an unrecognized list URL protocol', async () => {
+    const url = 'unknown://example.com/invalid-tokenlist.json'
+    fetch.mockOnceIf(url, () => Promise.resolve(''))
+    await expect(fetchTokenList(url, resolver)).rejects.toThrow(`Unrecognized list URL protocol.`)
+  })
+
+  it('logs a debug statement if the response is not successful', async () => {
+    const url = 'https://example.com/invalid-tokenlist.json'
+    fetch.mockOnceIf(url, () => Promise.resolve({ status: 404 }))
+    await expect(fetchTokenList(url, resolver)).rejects.toThrow(
+      `No valid token list found at any URLs derived from ${url}.`
+    )
+    expect(console.debug).toHaveBeenCalled()
+    expect(resolver).not.toHaveBeenCalled()
+  })
+
   it('fetches and validates the default token list', async () => {
     fetch.mockOnceIf(DEFAULT_TOKEN_LIST, () => Promise.resolve(JSON.stringify(defaultTokenList)))
     await expect(fetchTokenList(DEFAULT_TOKEN_LIST, resolver)).resolves.toStrictEqual(defaultTokenList)
     expect(resolver).not.toHaveBeenCalled()
   })
+
+  it('throws for a list with invalid json response', async () => {
+    const url = 'https://example.com/invalid-tokenlist.json'
+    fetch.mockOnceIf(url, () => Promise.resolve('invalid json'))
+    await expect(fetchTokenList(url, resolver)).rejects.toThrow(
+      `No valid token list found at any URLs derived from ${url}.`
+    )
+    expect(console.debug).toHaveBeenCalled()
+    expect(resolver).not.toHaveBeenCalled()
+  })
+
+  it('uses cached value the second time', async () => {
+    const url = 'https://example.com/invalid-tokenlist.json'
+    fetch.mockOnceIf(url, () => Promise.resolve(JSON.stringify(defaultTokenList)))
+    await expect(fetchTokenList(url, resolver)).resolves.toStrictEqual(defaultTokenList)
+    await expect(fetchTokenList(url, resolver)).resolves.toStrictEqual(defaultTokenList)
+    expect(fetch).toHaveBeenCalledTimes(1)
+  })
 })

src/lib/hooks/useTokenList/fetchTokenList.ts

@@ -8,7 +8,11 @@ export const DEFAULT_TOKEN_LIST = 'https://gateway.ipfs.io/ipns/tokens.uniswap.o
 
 const listCache = new Map<string, TokenList>()
 
-/** Fetches and validates a token list. */
+/**
+ * Fetches and validates a token list.
+ * For a given token list URL, we try to fetch the list from all the possible HTTP URLs.
+ * For example, IPFS URLs can be fetched through multiple gateways.
+ */
 export default async function fetchTokenList(
   listUrl: string,
   resolveENSContentHash: (ensName: string) => Promise<string>,
@@ -43,31 +47,38 @@ export default async function fetchTokenList(
     urls = uriToHttp(listUrl)
   }
 
+  if (urls.length === 0) {
+    throw new Error('Unrecognized list URL protocol.')
+  }
+
+  // Try each of the derived URLs until one succeeds.
   for (let i = 0; i < urls.length; i++) {
     const url = urls[i]
-    const isLast = i === urls.length - 1
     let response
     try {
       response = await fetch(url, { credentials: 'omit' })
     } catch (error) {
-      const message = `failed to fetch list: ${listUrl}`
-      console.debug(message, error)
-      if (isLast) throw new Error(message)
+      console.debug(`failed to fetch list: ${listUrl} (${url})`, error)
       continue
     }
 
     if (!response.ok) {
-      const message = `failed to fetch list: ${listUrl}`
-      console.debug(message, response.statusText)
-      if (isLast) throw new Error(message)
+      console.debug(`failed to fetch list ${listUrl} (${url})`, response.statusText)
       continue
     }
 
+    try {
+      // The content of the result is sometimes invalid even with a 200 status code.
+      // A response can be invalid if it's not a valid JSON or if it doesn't match the TokenList schema.
       const json = await response.json()
       const list = skipValidation ? json : await validateTokenList(json)
       listCache?.set(listUrl, list)
       return list
+    } catch (error) {
+      console.debug(`failed to parse and validate list response: ${listUrl} (${url})`, error)
+      continue
+    }
   }
 
-  throw new Error('Unrecognized list URL protocol.')
+  throw new Error(`No valid token list found at any URLs derived from ${listUrl}.`)
 }