Fully deserialize as necessary to look up pointers

Fixes #66.

Co-authored-by: Mark Wubben <[email protected]>

lib/recursorUtils.js

@@ -24,6 +24,22 @@ function fork (recursor) {
 }
 exports.fork = fork
 
+function consumeDeep (recursor) {
+  const stack = [recursor]
+  while (stack.length > 0) {
+    const subject = stack[stack.length - 1]()
+    if (subject === null) {
+      stack.pop()
+      continue
+    }
+
+    if (typeof subject.createRecursor === 'function') {
+      stack.push(subject.createRecursor())
+    }
+  }
+}
+exports.consumeDeep = consumeDeep
+
 function map (recursor, mapFn) {
   return () => {
     const next = recursor()

lib/serialize.js

@@ -16,13 +16,15 @@ const promiseValue = require('./complexValues/promise')
 const regexpValue = require('./complexValues/regexp')
 const setValue = require('./complexValues/set')
 const typedArrayValue = require('./complexValues/typedArray')
+
 const encoder = require('./encoder')
 
 const itemDescriptor = require('./metaDescriptors/item')
 const mapEntryDescriptor = require('./metaDescriptors/mapEntry')
 const pointerDescriptor = require('./metaDescriptors/pointer')
 const propertyDescriptor = require('./metaDescriptors/property')
 const statsDescriptors = require('./metaDescriptors/stats')
+
 const pluginRegistry = require('./pluginRegistry')
 
 const bigIntValue = require('./primitiveValues/bigInt')
@@ -33,6 +35,8 @@ const stringValue = require('./primitiveValues/string')
 const symbolValue = require('./primitiveValues/symbol')
 const undefinedValue = require('./primitiveValues/undefined')
 
+const recursorUtils = require('./recursorUtils')
+
 // Increment if encoding layout, descriptor IDs, or value types change. Previous
 // Concordance versions will not be able to decode buffers generated by a newer
 // version, so changing this value will require a major version bump of
@@ -317,12 +321,27 @@ function deserialize (buffer, options) {
   const descriptorsByPointerIndex = new Map()
   const mapPointerDescriptor = descriptor => {
     if (descriptor.isPointer === true) {
-      if (!descriptorsByPointerIndex.has(descriptor.index)) throw new PointerLookupError(descriptor.index)
+      if (descriptorsByPointerIndex.has(descriptor.index)) {
+        return descriptorsByPointerIndex.get(descriptor.index)
+      }
+
+      if (typeof rootDescriptor.createRecursor === 'function') {
+        // The descriptor we're pointing to may be elsewhere in the serialized
+        // structure. Consume the entire structure and check again.
+        recursorUtils.consumeDeep(rootDescriptor.createRecursor())
+
+        if (descriptorsByPointerIndex.has(descriptor.index)) {
+          return descriptorsByPointerIndex.get(descriptor.index)
+        }
+      }
+
+      throw new PointerLookupError(descriptor.index)
+    }
 
-      return descriptorsByPointerIndex.get(descriptor.index)
-    } else if (descriptor.isComplex === true) {
+    if (descriptor.isComplex === true) {
       descriptorsByPointerIndex.set(descriptor.pointer, descriptor)
     }
+
     return descriptor
   }
 
@@ -335,6 +354,8 @@ function deserialize (buffer, options) {
       return mapPointerDescriptor(deserializeDescriptor(state, recursor))
     }
   }
-  return deserializeRecord(decoded.rootRecord, getDescriptorDeserializer, buffer)
+
+  const rootDescriptor = deserializeRecord(decoded.rootRecord, getDescriptorDeserializer, buffer)
+  return rootDescriptor
 }
 exports.deserialize = deserialize

test/diff.js

@@ -1,5 +1,6 @@
 const test = require('ava')
 
+const concordance = require('..')
 const { diff: _diff } = require('../lib/diff')
 
 const { theme, normalizedTheme, checkThemeUsage } = require('./_instrumentedTheme')
@@ -525,3 +526,24 @@ test('objects: effectively resets depth when formatting differences', t => {
   }
   t.snapshot(_diff(o1, o2, { maxDepth: 1, theme }))
 })
+
+// See <https://github.com/concordancejs/concordance/issues/66>.
+test('diff pointers hidden behind maxDepth', t => {
+  const value = {}
+  const descriptor = concordance.describe({
+    // `value` is encoded in the serialization of `a.b`. `c` is encoded as a
+    // pointer to the encoded `value`.
+    a: {
+      b: value,
+    },
+    c: value,
+  })
+  const serialized = concordance.serialize(descriptor)
+
+  t.notThrows(() => {
+    // `maxDepth: 1` means that `a.b` is not normally deserialized, and so the
+    // `c` pointer cannot be resolved, unless the resolution logic first
+    // deserializes the descriptor in its entirety.
+    concordance.diffDescriptors(concordance.deserialize(serialized), concordance.describe(undefined), { maxDepth: 1 })
+  })
+})

test/format.js

@@ -1,5 +1,6 @@
 const test = require('ava')
 
+const concordance = require('..')
 const { format: _format } = require('../lib/format')
 const { theme, normalizedTheme, checkThemeUsage } = require('./_instrumentedTheme')
 const customErrorPlugin = require('./fixtures/customErrorPlugin')
@@ -434,3 +435,24 @@ test('format with given plugin', t => {
   const actual2 = _format(new Error('error'), { plugins, theme })
   t.snapshot(actual2)
 })
+
+// See <https://github.com/concordancejs/concordance/issues/66>.
+test('format pointers hidden behind maxDepth', t => {
+  const value = {}
+  const descriptor = concordance.describe({
+    // `value` is encoded in the serialization of `a.b`. `c` is encoded as a
+    // pointer to the encoded `value`.
+    a: {
+      b: value,
+    },
+    c: value,
+  })
+  const serialized = concordance.serialize(descriptor)
+
+  t.notThrows(() => {
+    // `maxDepth: 1` means that `a.b` is not normally deserialized, and so the
+    // `c` pointer cannot be resolved, unless the resolution logic first
+    // deserializes the descriptor in its entirety.
+    concordance.formatDescriptor(concordance.deserialize(serialized), { maxDepth: 1 })
+  })
+})