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spec: allow import to merge service definitions #504

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merged 5 commits into from
Dec 15, 2023
Merged

spec: allow import to merge service definitions #504

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39fa4c2
spec: allow import to merge service definitions
chenyan-dfinity Dec 13, 2023
63145ef
rename to import_service, and disallow service constructor
chenyan-dfinity Dec 13, 2023
abdc405
rename to import service
chenyan-dfinity Dec 14, 2023
65d21a3
Update spec/Candid.md
chenyan-dfinity Dec 15, 2023
b539b86
Merge branch 'master' into import-spec
chenyan-dfinity Dec 15, 2023
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13 changes: 7 additions & 6 deletions spec/Candid.md
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Expand Up @@ -64,7 +64,7 @@ The purpose of an IDL is defining the signature, and thereby the *type* of an ac
This is a summary of the grammar proposed:
```
<prog> ::= <def>;* <actor>?
<def> ::= type <id> = <datatype> | import <text> | import* <text>
<def> ::= type <id> = <datatype> | import service? <text>
<actor> ::= service <id>? : (<tuptype> ->)? (<actortype> | <id>) ;?

<actortype> ::= { <methtype>;* }
Expand Down Expand Up @@ -519,14 +519,15 @@ type B = A; // error: cyclic type definition
In order to allow splitting interface definitions up into multiple files or share common definitions between multiple interfaces, *import* declarations are provided.

```
<def> ::= ... | import <text> | import* <text>
<def> ::= ... | import service? <text>
```

There are two forms of import: `import` and `import*`. Both `import` and `import*` refer to another interface file by URL. The type definitions from the imported file are textually included in the importing file. The definitions from the imported file must not refer to definitions from the importing file.
An import refers to another interface file by URL. The type definitions from the imported file are textually included in the importing file. The definitions from the imported file must not refer to definitions from the importing file.

In addition, `import*` includes the main service from the imported file and merges the service definition with the main service in the importing file. The methods in the imported file must not have the same name as the importing file.
`import` ignores the main service definition from the imported file, while `import service` includes the main service from the imported file and merges the service definition with the main service in the importing file. There are two constraints with the main service definition in the imported file:

`import` ignores the main service definition from the imported file.
* The main service cannot be a service constructor.
* The methods from the imported file must not have the same method name as the importing file.

##### Example

Expand All @@ -537,7 +538,7 @@ service : A
```
File `B.did`:
```
import "A.did"; // Cannot use import* because of method name duplication
import "A.did"; // Cannot use import_service because of method name duplication
service B : A ;
```

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