feat: allow shared named snapshot close #443

README.md

@@ -157,6 +157,16 @@ exports['my name'] = 42
 
 **Note** you should make sure that the name is unique per spec file.
 
+### Shared snapshot name
+
+If you **do want** to share a named snapshot value from several places or tests in the same spec file, you need to pass an option when calling `snapshot`. The the first snapshot is saved, and the next ones will just compare against the value.
+
+```js
+snapshot('my shared snapshot', value, { allowSharedSnapshot : true })
+// some time later
+snapshot('my shared snapshot', value, { allowSharedSnapshot : true })
+```
+
 ## Pruning
 
 If the test run is successful and executed _all_ tests (there was no `.only`) then snapshots without a test are pruned. You can skip pruning by running with environment variable

__snapshots__/named-snapshots-spec.js

@@ -5,3 +5,5 @@ exports['my snap name'] = 41
 exports['second snapshot'] = 2
 
 exports['third snapshot'] = 3
+
+exports['shared snapshot'] = 42

src/duplicate-key-spec.js

@@ -40,6 +40,8 @@ describe('duplicate key', () => {
           }
         )
       )
+      // it is fine to use the same snapshot name if passed an option
+      snapshot('diff values', 1, { allowSharedSnapshot: true })
     })
   })
 })

src/index.js

@@ -52,23 +52,26 @@ const isPruneInfo = is.schema({
   specFile: is.unemptyString,
   key: is.unemptyString,
   testTitle: is.unemptyString,
-  titleParts: is.strings
+  titleParts: is.strings,
+  allowDuplicate: is.bool
 })
 
 function addToPrune (info) {
   la(isPruneInfo(info), 'wrong info for pruning snapshot', info)
 
   const prevInfo = findExistingSnapshotKey(info)
-  if (prevInfo) {
-    debug('found duplicate snapshot name: %s', prevInfo.key)
+  if (prevInfo && !info.allowDuplicate) {
+    debug('add to prune: found duplicate snapshot name: %s', prevInfo.key)
+    debug('%o', info)
+
     throwDuplicateSnapshotKeyError(info, prevInfo)
   }
 
   seenSpecs.push(info)
 }
 
 const findExistingSnapshotKey = info => {
-  la(isPruneInfo(info), 'wrong snapshot info', info)
+  la(isPruneInfo(info), 'wrong snapshot prune info', info)
   return R.find(R.propEq('key', info.key))(seenSpecs)
 }
 
@@ -183,6 +186,7 @@ function snapshot (value) {
 
   // eslint-disable-next-line immutable/no-let
   let savedTestTitle = fullTitle
+  let snapshotOptions = {}
 
   if (isDataDriven(arguments)) {
     // value is a function
@@ -194,6 +198,8 @@ function snapshot (value) {
   } else if (isNamedSnapshotArguments(arguments)) {
     savedTestTitle = arguments[0]
     value = arguments[1]
+    // and there could be additional arguments for named snapshots
+    snapshotOptions = arguments[2] || {}
     debug('named snapshots "%s"', savedTestTitle)
   } else {
     debug('snapshot value %j', value)
@@ -290,6 +296,7 @@ function snapshot (value) {
     la('key' in coreResult, 'core result should have key', coreResult)
 
     const pruneInfo = R.assoc('key', coreResult.key, snapshotInfo)
+    pruneInfo.allowDuplicate = Boolean(snapshotOptions.allowSharedSnapshot)
     debug('prune info %o', pruneInfo)
 
     addToPrune(pruneInfo)
@@ -307,7 +314,9 @@ function snapshot (value) {
       // })
       //
       // check if we have a collision
+      // the code is duplicate from above to get just the key collision error
       const info = R.assoc('key', e.key, snapshotInfo)
+      info.allowDuplicate = Boolean(snapshotOptions.allowSharedSnapshot)
       debug('current snapshot info %o', info)
 
       const prevInfo = findExistingSnapshotKey(info)

src/named-snapshots-spec.js

@@ -18,4 +18,22 @@ describe('named snapshots', () => {
       la(e.message.includes(mySnapshotName), e.message)
     }
   })
+
+  context('allows several tests to use same name', () => {
+    const snapshotName = 'shared snapshot'
+
+    // as long as the value is the same, these two tests
+    // should be allowed to use same snapshot name
+    const snapshotOptions = {
+      allowSharedSnapshot: true
+    }
+
+    it('test a', () => {
+      snapshot(snapshotName, 42, snapshotOptions)
+    })
+
+    it('test b', () => {
+      snapshot(snapshotName, 42, snapshotOptions)
+    })
+  })
 })

src/named-snapshots.js

@@ -1,7 +1,12 @@
 const is = require('check-more-types')
 
+/**
+ * If we called snapshot like `snapshot('name', value)`
+ * or like `snapshot('name', value, options)` then this is
+ * a named snapshot.
+ */
 function isNamedSnapshotArguments (args) {
-  return args.length === 2 && is.string(args[0])
+  return (args.length === 2 || args.length === 3) && is.string(args[0])
 }
 
 // eslint-disable-next-line immutable/no-mutation