Model resolution registry #91
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Toucan allows to query a model by either the model itself or the symbol of the model `(db/select 'User :id 1)`. This lookup will look at `models/root-namespace` for a model namespace. But this lookup will obviously fail if you define models in namespaces that do not follow this convention. For example multiple models in the same namespace cannot possibly work. This branch was added under the standard lookup so as not to be a breaking change. In either order there is the chance for ambiguity. Defining two models with the same name will never be well-defined. Under this change, it will always find the model defined by convention and never the one in a non-standard location. This ambiguity cannot actually be fixed since there is no disambiguating information in the query `(select 'Foo :id 1)`.
If there are multiple namespaces defining a model by the same name right now, it will always resolve to one at the conventional location. Before this change, no unconventional location models would ever be found by using the symbol. This explains why the lookup by model symbol is the second branch (so the current behavior, while unspecified before, continues in the same manner), and why we do not choose an item if multiple namespaces are registered (arbitrary model by set order, or last namespace read if we just keep one namespace).
dpsutton
force-pushed
the
model-resolution-registry
branch
from
0a39bf5
to
e955ccc
Compare
|
If we're willing to break a bit to error when there are multiple models and a query uses a model symbol, (defn- resolve-model-from-symbol
[symb]
(letfn [(sym->model-var [ns' symb']
(try
(requiring-resolve (symbol (str ns') (str symb')))
(catch java.io.FileNotFoundException _e nil)))]
(let [inferred-ns (model-symb->ns symb)
registered-nss (get @models/model-sym->namespace-sym symb)
[model-var & ambig] (->> (conj registered-nss inferred-ns)
(keep #(sym->model-var % symb)))]
(cond
(not model-var)
(throw (ex-info (format "Could not find model for: %s" symb)
{:symbol symb
:configured-namespace inferred-ns
:registered-namespaces registered-nss}))
(seq ambig)
(throw (ex-info (format "Found multiple models for: %s" symb)
{:symbol symb
:configured-namespace inferred-ns
:registered-namespaces registered-nss
:vars (conj ambig model-var)}))
:else
(deref model-var))))) |
|
I think the expectation is that models are unique anyway so erroring if there are duplicates would be fine if you wanted to open a follow-on PR to do that... but I'll merge this as-is and cut a new release |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Changes:
add a model registry from model symbol to set of namespaces that defines it. Use this registry to look up when model is used as a symbol, eg
(db/select 'Foo :id 1).Suggested breaking change
Before this change, defining multiple models with the same name and querying by model symbol would always resolve to the model defined in the "conventional" namespace as constructed with
model/root-namespace. If there were multiple models defined in "unconventional" locations, it would never find either of them. The registry is checked after the inferred namespace to preserve this behavior. But it might be better to change this behavior. Rather than allowing multiple model definitions like this, perhaps we could check the inferred location and also the registered locations and ensure we do not have an ambiguous model reference.There is probably a small chance of this happening but having models findable in non-standard locations might increase the odds of it a little bit.
ie, if you define a normal model
Userin the conventional location ((defmodel User :production_user_table)) and a test file defines(defmodel User :test_user_table), usages of'Useras a symbol would resolve to the production user table. It might be better to throw in this case, even if this is a remote scenario.