fix: add support for resolving to the middle of an IPLD block (#1841)

refs ipfs-inactive/interface-js-ipfs-core#385
resolves #1763

BREAKING CHANGE: `ipfs.resolve` now supports resolving to the middle of an IPLD block instead of erroring.

Given:

```js
b = {"c": "some value"}
a = {"b": {"/": cidOf(b) }}
```

`ipfs resolve /ipld/cidOf(a)/b/c` should return `/ipld/cidOf(b)/c`. That is, it resolves the path as much as it can.

Previously it would simply fail with an error.

License: MIT
Signed-off-by: Alan Shaw <alan.shaw@protocol.ai>

Author: Stebalien

.aegir.js

@@ -15,7 +15,7 @@ module.exports = {
   },
   karma: {
     files: [{
-      pattern: 'node_modules/interface-ipfs-core/js/test/fixtures/**/*',
+      pattern: 'node_modules/interface-ipfs-core/test/fixtures/**/*',
       watched: false,
       served: true,
       included: false

package.json

@@ -68,7 +68,7 @@
     "execa": "^1.0.0",
     "form-data": "^2.3.3",
     "hat": "0.0.3",
-    "interface-ipfs-core": "~0.96.0",
+    "interface-ipfs-core": "~0.97.0",
     "ipfsd-ctl": "~0.41.0",
     "libp2p-websocket-star": "~0.10.2",
     "ncp": "^2.0.0",

src/core/components/resolve.js

@@ -34,17 +34,16 @@ module.exports = (self) => {
 
     const path = split.slice(3).join('/')
 
-    resolve(cid, path, (err, cid) => {
+    resolve(cid, path, (err, res) => {
       if (err) return cb(err)
-      if (!cid) return cb(new Error('found non-link at given path'))
-      cb(null, `/ipfs/${cidToString(cid, { base: opts.cidBase })}`)
+      const { cid, remainderPath } = res
+      cb(null, `/ipfs/${cidToString(cid, { base: opts.cidBase })}${remainderPath ? '/' + remainderPath : ''}`)
     })
   })
 
   // Resolve the given CID + path to a CID.
   function resolve (cid, path, callback) {
-    let value
-
+    let value, remainderPath
     doUntil(
       (cb) => {
         self.block.get(cid, (err, block) => {
@@ -59,28 +58,31 @@ module.exports = (self) => {
           r.resolver.resolve(block.data, path, (err, result) => {
             if (err) return cb(err)
             value = result.value
-            path = result.remainderPath
+            remainderPath = result.remainderPath
             cb()
           })
         })
       },
       () => {
-        const endReached = !path || path === '/'
-
-        if (endReached) {
-          return true
-        }
-
-        if (value) {
+        if (value && value['/']) {
+          // If we've hit a CID, replace the current CID.
           cid = new CID(value['/'])
+          path = remainderPath
+        } else if (CID.isCID(value)) {
+          // If we've hit a CID, replace the current CID.
+          cid = value
+          path = remainderPath
+        } else {
+          // We've hit a value. Return the current CID and the remaining path.
+          return true
         }
 
-        return false
+        // Continue resolving unless the path is empty.
+        return !path || path === '/'
       },
       (err) => {
         if (err) return callback(err)
-        if (value && value['/']) return callback(null, new CID(value['/']))
-        callback()
+        callback(null, { cid, remainderPath: path })
       }
     )
   }

test/gateway/index.js

@@ -12,7 +12,7 @@ const path = require('path')
 const hat = require('hat')
 const fileType = require('file-type')
 
-const bigFile = loadFixture('js/test/fixtures/15mb.random', 'interface-ipfs-core')
+const bigFile = loadFixture('test/fixtures/15mb.random', 'interface-ipfs-core')
 const directoryContent = {
   'index.html': loadFixture('test/gateway/test-folder/index.html'),
   'nested-folder/hello.txt': loadFixture('test/gateway/test-folder/nested-folder/hello.txt'),