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[docs] Initial draft of the REST style guide - #1649
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Pull request overview
Adds a new REST documentation section to the Moodle DevDocs site, including an initial (but intended-to-be-normative) REST API style guide to standardize URI structure, naming, payload conventions, and HTTP semantics across Moodle components.
Changes:
- Introduces a comprehensive REST API style guide covering resource design, URI conventions, JSON conventions, pagination, errors, and idempotency.
- Adds a
RESTguide index page underdocs/guides/rest/.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 10 comments.
| File | Description |
|---|---|
| docs/guides/rest/style.md | Adds the initial REST style guide content and examples. |
| docs/guides/rest/index.md | Adds the REST guides section index frontmatter (and should include navigational content). |
Comments suppressed due to low confidence (2)
docs/guides/rest/style.md:998
- This TODO note also uses broken Markdown emphasis ("-*TO DO:**"). Formatting it consistently will improve readability of the draft.
-*TO DO:** this section is under revision; most of it is being removed as incorrect, so its rationale will be drafted once the replacement content is agreed.
docs/guides/rest/index.md:7
docs/guides/rest/index.mdcurrently contains only frontmatter, so the rendered page will be empty. Adding a short introduction and links (e.g. to the style guide) will make the section navigable.
---
| GET /courses/{courseid} | ||
| POST /courses | ||
| PATCH /courses/{courseid} | ||
| DELETE /courses/{courseid} |
| ### 7.1 Nested Resources | ||
| Nested resources MUST only be used only for direct ownership or containment relationships. |
| { | ||
| "courseId": 42, | ||
| "shortName": "math101", | ||
| "createdAt": 1779193800, | ||
| "startDate": 1779193800 | ||
| } |
| "pagination": { | ||
| "page": 1, | ||
| "pagesize": 25, | ||
| "totalitems": 1 | ||
| } | ||
| } |
| "pagination": { | ||
| "page": 1, | ||
| "pagesize": 25, | ||
| "totalitems": 100 | ||
| } | ||
| } |
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| #### RATIONALE | ||
| -*TO DO:** this rationale needs further work — the scope naming examples in this section are still under review and will be revised before this rationale is finalized. |
| - OAuth2 | ||
| - ****** Service tokens | ||
| #### RATIONALE | ||
| Declarative payloads describe what the resource should look like afterwards, which is idempotent, easy to validate against a schema, and safe to retry. Imperative payloads like "move": "up" encode a transition rather than a state, so retries or race conditions between two clients could produce different results depending on execution order, undermining PATCH's idempotency expectations from section 15.2. |
| /courses/{courseid}/sections | ||
| /mod_forum/It was /{discussionid}/posts/{postid} |
| | Canonical Patterns | reusable API patterns | | ||
| | Rationale | explanatory guidance | | ||
| Normative sections MUST use only: |
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Can we quote or reference RFC 2119 and 8174 here? I know, this is not an Internet Standard, but RFC 2119 was created for a reason, and IMHO it fits very well here, too.
| Normative sections MUST use only: | |
| Normative sections MUST use only the following key words, and they are to be interpreted as described in [BCP 14](https://datatracker.ietf.org/doc/html/bcp14)[[RFC2119](https://datatracker.ietf.org/doc/html/rfc2119)][[RFC8174](https://datatracker.ietf.org/doc/html/rfc8174)] when, and only when, they appear in all capitals: |
| ## 3. Core REST Principles | ||
| All Moodle APIs MUST satisfy **Richardson Maturity Model Level 2**. |
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We should include a link to a normative source so that people unfamiliar with the model can read about it.
| All Moodle APIs MUST satisfy **Richardson Maturity Model Level 2**. | |
| All Moodle APIs MUST satisfy **[Richardson Maturity Model Level 2](https://martinfowler.com/articles/richardsonMaturityModel.html)**. |
| | 404 | Resource not found | | ||
| | 409 | Conflict | | ||
| | 422 | Validation failure | |
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Section 15.1 also mentions 412 Precondition Failed, so we should include it here.
| | 404 | Resource not found | | |
| | 409 | Conflict | | |
| | 422 | Validation failure | | |
| | 404 | Resource not found | | |
| | 409 | Conflict | | |
| | 412 | Precondition Failed | | |
| | 422 | Validation failure | |
| | PUT | Yes | | ||
| | DELETE | Yes | | ||
| | POST | No | | ||
| | PATCH | No guarantee | |
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Minor: Can we simplify PATCH just "No" instead of "No guarantee"?
| | POST | No | | ||
| | PATCH | No guarantee | | ||
| Retryable POST operations SHOULD support: |
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Thoughts about upgrading Idempotency-Key from SHOULD to MUST?
- This would make retry safety a first principle. See my other comment below.
- In general, fewer optionality reduces ambiguity and thus complexity.
Of course, the downside is slightly more client-side complexity. But in my opinion is well worth not having to deal with support calls about duplicate records due to retries.
| #### RATIONALE | ||
| Clients on unreliable networks, particularly mobile, need to safely retry requests without accidentally creating duplicate resources; since POST is inherently non-idempotent, an explicit Idempotency-Key lets the server recognize and deduplicate a retried creation request as the same logical operation, rather than the client having to guess whether a prior request actually succeeded before retrying. |
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It's not just network unreliability but rather unreliability in general, which would include server overload, especially during the start of semester (leading to duplicate requests).
jtse
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Thanks for writing this! A general point: Consider having fewer SHOULDs, either upgrading them to MUST or removing them. SHOULD in specs tend to make things more complicated.
| Rules: | ||
| - must represent clear hierarchical ownership | ||
| - must remain shallow (maximum recommended depth: 2) |
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+1 to shallow resources (especially with respect to the technical reasons you outlined below). Where would a common resource like student submissions for an activity (assignment) go? If it's nested under activities it would be a depth of 3.
On the other hand, that nesting also feels intuitive to me as a dev. Maybe one way to resolve this is the top level resource courses (and enrollment) don't change often especially later in the school year/semester, so it's highly cacheable.
Thoughts?
jtse
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Looking forward to seeing how this evolves and prototype implementations.
This is the initial draft of the REST style guide for RFC.