Answers.Body: <p>I had a stupid typo in my path, where instead of the <code>date</code> filter, I'd typed <code>dateCreated</code>:</p>
  
  <pre><code>/our-journal/{ entry.dateCreated|date('Y-m') ?: now|dateCreated('Y-m') }/{ slug }
  </code></pre>
  
  <p>Should be:</p>
  
  <pre><code>/our-journal/{ entry.dateCreated|date('Y-m') ?: now|date('Y-m') }/{ slug }
  </code></pre>
  
  <p>Which, with what I learnt about fallbacks (see below), can be shortened to:</p>
  
  <pre><code>/our-journal/{ entry.dateCreated|date('Y-m') }/{ slug }
  </code></pre>
  
  <p>And if you're doing this within a matrix field, the entry is referred to by <code>owner</code> - so you'd need:</p>
  
  <pre><code>/our-journal/{ owner.dateCreated|date('Y-m') }/{ owner.slug }/
  </code></pre>
  
  <p><strong>Fallbacks</strong></p>
  
  <p>I also found that I didn't need to provide fallbacks for entry tags - I'd thought that I'd need to provide a fallback for when a new entry hasn't yet been saved (to stop it falling over on e.g. <code>dateCreated</code>).</p>
  
  <p>It appears that Craft is clever enough to hold the image in some temporary store, then move it into the intended folder when the article is first saved.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-11-02T10:07:10.873Z
Answers.LastActivityDate: 2017-11-02T10:43:55.973Z
Answers.LastEditDate: 2017-11-02T10:43:55.973Z
Answers.UserDisplayName: Adam Hopkinson
Body: <p>I'm trying to set a default asset folder for a field, as per the Craft docs on <a href="https://craftcms.com/docs/assets-fields#dynamic-subfolder-paths" rel="nofollow noreferrer">Dynamic Subfolder Paths</a>.</p>
  
  <p>I'm trying to set the asset path for each blog article to be <code>/our-journal/{date}/{slug}</code>, where date is the creation date of the article, falling back to today's date otherwise.</p>
  
  <pre><code>/our-journal/{ entry.dateCreated|date('Y-m') ?: now|dateCreated('Y-m') }/{ slug }
  </code></pre>
  
  <p>I'm getting an internal server error:</p>
  
  <blockquote>
    <p>Could not resolve the subpath “our-journal/{ entry.dateCreated|date('Y-m') ?: now|dateCreated('Y-m') }/{ slug }”.</p>
  </blockquote>
  
  <p>I've tried using both single and double braces around the variables, as the docs are a bit ambiguous.</p>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-11-01T18:45:12.770Z
Comments.Text: Is Asset field inside of a Matrix field?
Comments.UserDisplayName: Brad Bell
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-11-02T09:06:22.497Z
Comments.Text: I've got the default path on two fields - one on the entry and one in a matrix field on the same entry type. As far as I can see, it's the field directly on the entry that is causing the issue (probably both are, but that one is hitting validation first).
Comments.UserDisplayName: Adam Hopkinson
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-11-02T10:07:53.373Z
Comments.Text: Thanks for your help @BradBell, I found a stupid typo. Also found something interesting about how Craft handles asset uploads on unsaved entries - see my answer below.
Comments.UserDisplayName: Adam Hopkinson
Tags: <assets><field><tags>
Title: Trying to set a default asset folder using Craft tags
ThreadText: # Trying to set a default asset folder using Craft tags
  
  (Asked by: username_0 on 2017-11-01)
  
  I'm trying to set a default asset folder for a field, as per the Craft docs on [Dynamic Subfolder Paths](https://craftcms.com/docs/assets-fields#dynamic-subfolder-paths).
  
  I'm trying to set the asset path for each blog article to be `/our-journal/{date}/{slug}`, where date is the creation date of the article, falling back to today's date otherwise.
  
  ```
  /our-journal/{ entry.dateCreated|date('Y-m') ?: now|dateCreated('Y-m') }/{ slug }
  
  ```
  
  I'm getting an internal server error:
  
  > Could not resolve the subpath “our-journal/{ entry.dateCreated|date('Y-m') ?: now|dateCreated('Y-m') }/{ slug }”.
  
  I've tried using both single and double braces around the variables, as the docs are a bit ambiguous.
  
  **Tags:** assets, field, tags
  
  > **Comments:**
  > **username_1**: Is Asset field inside of a Matrix field?  
  > **username_0**: I've got the default path on two fields - one on the entry and one in a matrix field on the same entry type. As far as I can see, it's the field directly on the entry that is causing the issue (probably both are, but that one is hitting validation first).  
  > **username_0**: Thanks for your help @username_1, I found a stupid typo. Also found something interesting about how Craft handles asset uploads on unsaved entries - see my answer below.  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_0 on 2017-11-02. Score: 1
  
  I had a stupid typo in my path, where instead of the `date` filter, I'd typed `dateCreated`:
  
  ```
  /our-journal/{ entry.dateCreated|date('Y-m') ?: now|dateCreated('Y-m') }/{ slug }
  
  ```
  
  Should be:
  
  ```
  /our-journal/{ entry.dateCreated|date('Y-m') ?: now|date('Y-m') }/{ slug }
  
  ```
  
  Which, with what I learnt about fallbacks (see below), can be shortened to:
  
  ```
  /our-journal/{ entry.dateCreated|date('Y-m') }/{ slug }
  
  ```
  
  And if you're doing this within a matrix field, the entry is referred to by `owner` - so you'd need:
  
  ```
  /our-journal/{ owner.dateCreated|date('Y-m') }/{ owner.slug }/
  
  ```
  
  **Fallbacks**
  
  I also found that I didn't need to provide fallbacks for entry tags - I'd thought that I'd need to provide a fallback for when a new entry hasn't yet been saved (to stop it falling over on e.g. `dateCreated`).
  
  It appears that Craft is clever enough to hold the image in some temporary store, then move it into the intended folder when the article is first saved.
  
  
  ---
  
  