feat: Add rule 'No absolute DataSource Uri' for CF platform

[aleksandr-suvorov]

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According to Best Practices oDataSources uri shouldn't start with a leading slash / - it must be relative to the base url, see:

• Develop a Full-Stack CAP Application Following SAP BTP Developer’s Guide
• Accessing Business Service UI

[cla-assistant]

All committers have signed the CLA.

[coveralls]

coverage: 86.827% (+0.05%) from 86.782%
when pulling 1507dba on aleksandr-suvorov:feat-no-absolute-data-source-uri
into 9236745 on UI5:main.

[RandomByte]

How sure can we be that this autofix won't break applications? I suspect that many absolute URLs would resolve incorrectly when removing the leading slash without considering the location of the app. For example most of our CAP sample projects use absolute URLs that would break the app: https://github.com/SAP-samples/ui5-cap-event-app/blob/85c2557080f2945727ba0cc2b932add808a19c99/packages/ui-admin/webapp/manifest.json#L15

I would expect this restriction to be at least mentioned, but ideally validated in the manifest schema.

UI5 MCP server currently does not allow for creating apps with relative paths, only absolute: https://github.com/UI5/mcp-server/blob/5f678208e3c03f35eaee57c1c6cccfe6ce26c22d/src/tools/create_ui5_app/create_ui5_app.ts#L87

CC: @akudev

[codeworrior]

I think the check for an existing service configuration in the "sap.cloud" section is meant as a safeguard here.
Would however be nice to refer to a documentation that proves this check to be sufficient.

Expressing / enforcing something like this in the schema is IMO nearly impossible with JSON schema as one cannot describe restrictions based on siblings in the JSON tree - at least to my knowledge.

[RandomByte]

I see, thanks. So this check should only be applied if "sap.cloud".service is set to a string? A comment in the code would help understand this connection better.

Btw. what happens if an absolute URL is used on CF? I.e. what makes this rule necessary? Is this a common issue?

[flovogt]

For CF it is required to ZIP the build result and therefore usually the ui5-task-zipper is used which has a dedicated logic to remove the heading slash. See https://github.com/petermuessig/ui5-ecosystem-showcase/blob/main/packages/ui5-task-zipper/lib/zipper.js#L30-L38

[aleksandr-suvorov]

For https://github.com/SAP/ui5-task-adaptation we require prerequisites among others to be validated for CF, for example:

1. Restrict use of deprecated sap.ui.loadLibrary() and sap.ui.getCore().loadLibrary();
2. Validation of forward slashes in dataSources uri.

Validation 1. is already implemented in ui5Linter, so the 2. is necessary to be implemented in order to have prerequisites in one place - linting. Using ui5-task-zipper is also a good option, but it distributes meeting prerequisites in 2 different places.