Parse the Metadata from an SAP OData Service

This is a work in progress!

Parse the metadata XML describing an SAP OData service and generate Rust entities for each EDM type:

TODO

Currently when generating a Rust struct, only the Name and Type properties are extracted from the XML <EntityType> declaration.
Consider how the other XML attribute values and SAP annotations could be made available within the Rust struct.

Usage

Declare Build Dependency

In the Cargo.toml of your application, define an entry in [build-dependencies] that points to the parse-sap-odata crate:

toml [build-dependencies] parse-sap-odata = "^1.1.0"

Your app will also require these dependencies

toml [dependencies] rust_decimal = "^1.30" uuid = "^1.4" chrono = "^0.4"

Create a Build Script

In your app's build.rs, run the generator for your desired OData service:

```rust use parsesapodata::utils::parseodata::gensrc;

fn main() { // gensrc() requires two arguments // 1) metadatafilename: String The name of the XML file in the ./odata directory // Do not include the '.xml' suffix in the file name! // 2) namespace: String The namespace defined in the attribute of the OData XML gensrc("gwsamplebasic", "GWSAMPLEBASIC"); } ```

See the Rust documentation page for build scripts for more information.

XML Input Files

All metadata XML for the OData services your app consumes must be located in the ./odata directory immediately under your app's top level directory.

Generated Output

If cargo detects a build.rs file in your project/crate, then it automatically populates the environment variable OUT_DIR. This variable then points to the directory into which all build script output is written.

The default directory name will be target/debug/build/<your_package_name>/out, and this is where you can find the generated struct declarations for the OData service.

You can specify your own value for OUT_DIR either by calling cargo with the --out_dir flag, or by creating your own config.toml file in the ./cargo directory. See Cargo Configuration for more details.

Referencing Generated Output

In the source code of your application, the generated OData structs can be referenced like this:

```rust use chrono::Utc;

include!(concat!(env!("OUTDIR"), "/gwsamplebasic.rs"));

fn main() { let now = Utc::now().naiveutc(); let bp = BusinessPartner { address: Address { addresstype: Some(String::from("Dummay addres type")), building: Some(String::from("Dummy building")), city: Some(String::from("Dummy city")), country: Some(String::from("Dummy country")), postalcode: Some(String::from("Dummy postal code")), street: Some(String::from("Dummy street")), }, businesspartnerid: String::from("Dummy business partner id"), businesspartnerrole: String::from("Dummy business partner role"), changedat: Some(now), companyname: String::from("Dummy company name"), createdat: Some(now), currencycode: String::from("GBP"), emailaddress: String::from("Dummy email address"), faxnumber: Some(String::from("Dummy fax number")), legalform: Some(String::from("Dummy legal form")), phonenumber: Some(String::from("0123456789")), webaddress: Some(String::from("Dummy website address")), };

println!("{:#?}", bp);

} ```

OData Complex Types

In the event an Entity Type definition uses a complex type, then the complex type is first created as a Rust struct. The field in Rust struct that has this complex type is then defined using this struct.

An example of this is the Address property.

```xml

```

The Rust struct name is generated by trimming the namespace qualifier and (if present) the CT_ prefix

xml <ComplexType Name="CT_Address"> <Property Name="City" Type="Edm.String" MaxLength="40" sap:label="City" sap:semantics="city"/> <Property Name="PostalCode" Type="Edm.String" MaxLength="10" sap:label="Postal Code" sap:semantics="zip"/> <Property Name="Street" Type="Edm.String" MaxLength="60" sap:label="Street" sap:semantics="street"/> <Property Name="Building" Type="Edm.String" MaxLength="10" sap:label="Building"/> <Property Name="Country" Type="Edm.String" MaxLength="3" sap:label="Country" sap:semantics="country"/> <Property Name="AddressType" Type="Edm.String" MaxLength="2" sap:label="Address Type"/> </ComplexType>

So the above XML definition becomes:

```rust

[derive(Clone, Copy, Debug)]

pub struct Address { pub addresstype: Option, pub building: Option, pub city: Option, pub country: Option, pub postalcode: Option, pub street: Option, } ```

OData "Simple" Complex Types

The metadata for the GWSAMPLE_BASIC OData service contains the following complex type:

xml <ComplexType Name="CT_String"> <Property Name="String" Type="Edm.String" Nullable="false" sap:creatable="false" sap:updatable="false" sap:sortable="false" sap:filterable="false"/> </ComplexType>

Allowing for the current situation in which additional attribute values and SAP Annotations are not preserved, this particular type turns out not to be complex at all — its just a String. In such cases, fields declared to be of these "simple" complex types (such as CT_String), are collapsed down to the Rust native type of the single inner property — which in this example is simply a String.

TODOs

  1. Consider fetching the metadata at build time — but this raises the question of whether allowing a build script to look outside its sandbox is an anti-pattern...
  2. Support Function Imports

Testing this Crate Locally

  1. Clone this repo
  2. Change into the repo's build_test_crate subdirectory.
  3. Run cargo build
  4. Run ./target/debug/build-test-crate and you will see output similar to this:

rust BusinessPartner { address: Address { address_type: Some( "Dummy address type", ), building: Some( "Dummy building", ), city: Some( "Dummy city", ), country: Some( "Dummy country", ), postal_code: Some( "Dummy postal code", ), street: Some( "Dummy street", ), }, business_partner_id: "Dummy business partner id", business_partner_role: "Dummy business partner role", changed_at: Some( 2023-08-03T10:42:57.532857, ), company_name: "Dummy company name", created_at: Some( 2023-08-03T10:42:57.532857, ), currency_code: "GBP", email_address: "Dummy email address", fax_number: Some( "Dummy fax number", ), legal_form: Some( "Dummy legal form", ), phone_number: Some( "0123456789", ), web_address: Some( "Dummy website address", ), }