Closure-compiler: @typedef and @template don't work together

[agrafix]

The following code does not work:

/**
 * @template S, T
 * @typedef {{
 *             type: string,
 *             humanName: string,
 *             keyboard: TriResourceRef,
 *             serverElems: Array.<S>,
 *             getSrvId: function(S): string,
 *             getTitle: function(S): string,
 *             getDescriptions: function(S): Array.<string>,
 *             getUseForGrouping: function(S): boolean,
 *             getDeleted: function(S): boolean,
 *             getCliId: function(T): string,
 *             convertToSrv: function(T): S,
 *             convertToCli: function(S): T,
 *             makeNewCli: function(string, Date): T,
 *             mergeSrvCli: function(S, T): S,
 *             getUpdateId: function(T): string,
 *             isSent: function(T): boolean,
 *             insertDescriptionIfMissing: function(S): S
 *          }}
 */
var DrgInterf;

Using the recent compiler version, it results this:

/var/folders/m0/8vx31n6j775g80_0pqhh47k40000gn/T/tmpbDmD3e:77568: ERROR - Bad type annotation. Unknown type S
 *             serverElems: Array.<S>,
                                   ^

Splitting the template in two template annotations does not help either.

[concavelenz]

we should warn about a misplaced annotation with the use of @template described here. The @record proposal might allow this.

[silverlyra]

Is this ever going to be supported? We've got:

/**
 * @param {!function(F, null=, (Object<string,*>|null)=): !goog.soy.data.SanitizedContent} template
 * @template F
 */

pasted all over our codebase because it's impossible to have a parameterized @typedef 😒

[dimvar]

maybe, but it's not high priority so it might be a while

[shicks]

I think TypeScript allows adding some sort of "call" property to their interfaces. That might be one way to handle this, but allowing to define an @record (which can, of course, be templated) with a typed call method. In any case, if any approach is taken, it's not going to happen until after NTI is fully rolled out.

[mbrukman]

I'm also running into this issue. I'm trying to translate the TypeScript type annotations in Preact to Closure Compiler-compatible JsDoc (to be able to use Preact from a project which is compiled with Closure Compiler).

However, I cannot translate some of the types completely due to limitations with Closure Compiler support for @typedef and @template.

For example, consider the following TypeScript type in Preact:

type ComponentType<P = {}> = ComponentClass<P> | FunctionComponent<P>;

I would like to translate this to JsDoc as follows (note: I'm using a namespace preact for my @externs file):

/**
 * @typedef {preact.ComponentClass<P> | preact.FunctionComponent<P>}
 * @template P
 */
preact.ComponentType;

This file is then used as an @externs file, but it fails compilation with:

ERROR - Bad type annotation. Type name(s) for @template annotation declared twice. See https://github.com/google/closure-compiler/wiki/Annotating-JavaScript-for-the-Closure-Compiler for more information.

Unfortunately, that page does not say anything on the topic:

• the @template section doesn't talk about @typedef
• the @typedef section doesn't mention @template

Also, https://github.com/google/closure-compiler/wiki/Generic-Types doesn't mention anything about the interaction between @template and @typedef.

Removing the @template P annotation results in a different error:

ERROR - Bad type annotation. Unknown type P

As a result, I'm stuck, because I don't see a way to make it work.

---

If you'd like an isolated test case independent of Preact, consider the following file, similar to the above, without any @externs or other complexities:

/**
 * @typedef {Array<P> | Array<Q>}
 * @template P, Q
 */
var customArray;

Now, let's try to compile it:

$ java -jar closure-compiler-v20200719.jar --compilation_level=ADVANCED --dependency_mode=PRUNE \
      foo.js --entry_point foo.js \
foo.js:2: WARNING - [JSC_UNRECOGNIZED_TYPE_ERROR] Bad type annotation. Unknown type P
  2|  * @typedef {Array<P> | Array<Q>}
                        ^

foo.js:2: WARNING - [JSC_UNRECOGNIZED_TYPE_ERROR] Bad type annotation. Unknown type Q
  2|  * @typedef {Array<P> | Array<Q>}
                                   ^

foo.js:3: WARNING - [JSC_TYPE_PARSE_ERROR] Bad type annotation. Type name(s) for @template annotation declared twice. See https://github.com/google/closure-compiler/wiki/Annotating-JavaScript-for-the-Closure-Compiler for more information.
  3|  * @template P, Q
        ^

0 error(s), 3 warning(s)

---

I found some test cases that appear to generate the errors that I'm seeing, and I'm confused as to why they're considered errors:

https://github.com/google/closure-compiler/blob/3a22cab6d6d66642c1fd3b78040973a9a293e34c/test/com/google/javascript/jscomp/parsing/JsDocInfoParserTest.java#L2659-L2673

To me, these code samples look like exactly the correct thing for someone to write and expect to work when composing the use of @typedef with @template.