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Fix/@typescript eslint/no unnecessary condition #1483

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d4fd2e5
docs(binding-coap): document PSK usage with CoAPs
Pranav-0440 Feb 12, 2026
477dc14
docs(binding-coap): document PSK usage with CoAPs
Pranav-0440 Feb 13, 2026
bf19d2f
fix(binding-coap): align affordance forms typing and enable no-unnece…
Pranav-0440 Feb 15, 2026
583c2ce
style(binding-coap): fix prettier formatting
Pranav-0440 Feb 20, 2026
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69 changes: 69 additions & 0 deletions packages/binding-coap/README.md
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Expand Up @@ -52,6 +52,75 @@ servient
});
```

## Using PSK with CoAPs (DTLS)

The CoAP binding also supports secure communication over `coaps://` using DTLS with Pre-Shared Keys (PSK).

To use PSK security, define a `psk` security scheme in the Thing Description and provide the credentials when consuming the Thing.

### Thing Description Example (PSK)

```json
{
"title": "SecureThing",
"securityDefinitions": {
"psk_sc": {
"scheme": "psk"
}
},
"security": ["psk_sc"],
"properties": {
"count": {
"type": "integer",
"forms": [
{
"href": "coaps://localhost:5684/count"
}
]
}
}
}
```

### Client Example with PSK

```js
const { Servient } = require("@node-wot/core");
const { CoapClientFactory } = require("@node-wot/binding-coap");

const servient = new Servient();
servient.addClientFactory(new CoapClientFactory());

servient
.start()
.then(async (WoT) => {
try {
const td = await WoT.requestThingDescription("coaps://localhost:5684/secureThing");
const thing = await WoT.consume(td);

// configure PSK security
thing.setSecurity(td.securityDefinitions, {
identity: "Client_identity",
psk: "secretPSK",
});

const value = await thing.readProperty("count");
console.log("count value is:", await value.value());
} catch (err) {
console.error("Script error:", err);
}
})
.catch((err) => {
console.error("Start error:", err);
});
```

### Notes

- The `identity` must match the server configuration.
- The `psk` must match the server's configured secret.
- Currently, only the `psk` security scheme is supported for `coaps://` in this binding.

### Server Example

The server example produces a thing that allows for setting a property `count`. The thing is reachable through CoAP.
Expand Down
10 changes: 10 additions & 0 deletions packages/binding-coap/eslint.config.mjs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
import rootConfig from "../../eslint.config.mjs";

export default [
...rootConfig,
{
rules: {
"@typescript-eslint/no-unnecessary-condition": "warn",
},
},
];
21 changes: 15 additions & 6 deletions packages/binding-coap/src/coap-client.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -65,7 +65,9 @@ export default class CoapClient implements ProtocolClient {
debug(`CoapClient received Content-Format: ${res.headers["Content-Format"]}`);

// FIXME does not work with blockwise because of node-coap
const contentType = (res.headers["Content-Format"] as string) ?? form.contentType;
const rawContentType = res.headers["Content-Format"];
const contentType =
typeof rawContentType === "string" ? rawContentType : (form.contentType ?? ContentSerdes.DEFAULT);

resolve(new Content(contentType, Readable.from(res.payload)));
});
Expand Down Expand Up @@ -109,8 +111,11 @@ export default class CoapClient implements ProtocolClient {
debug(`CoapClient received ${res.code} from ${form.href}`);
debug(`CoapClient received Content-Format: ${res.headers["Content-Format"]}`);
debug(`CoapClient received headers: ${JSON.stringify(res.headers)}`);
const contentType = res.headers["Content-Format"] as string;
resolve(new Content(contentType ?? "", Readable.from(res.payload)));

const rawContentType = res.headers["Content-Format"];
const contentType = typeof rawContentType === "string" ? rawContentType : ContentSerdes.DEFAULT;

resolve(new Content(contentType, Readable.from(res.payload)));
});
req.on("error", (err: Error) => reject(err));
(async () => {
Expand Down Expand Up @@ -156,10 +161,12 @@ export default class CoapClient implements ProtocolClient {
debug(`CoapClient received Content-Format: ${res.headers["Content-Format"]}`);

// FIXME does not work with blockwise because of node-coap
const contentType = res.headers["Content-Format"] ?? form.contentType ?? ContentSerdes.DEFAULT;
const rawContentType = res.headers["Content-Format"];
const contentType =
typeof rawContentType === "string" ? rawContentType : (form.contentType ?? ContentSerdes.DEFAULT);

res.on("data", (data: Buffer) => {
next(new Content(`${contentType}`, Readable.from(res.payload)));
next(new Content(contentType, Readable.from(res.payload)));
});

resolve(
Expand Down Expand Up @@ -190,7 +197,9 @@ export default class CoapClient implements ProtocolClient {
req.setOption("Accept", "application/td+json");
return new Promise<Content>((resolve, reject) => {
req.on("response", (res: IncomingMessage) => {
const contentType = (res.headers["Content-Format"] as string) ?? "application/td+json";
const rawContentType = res.headers["Content-Format"];
const contentType = typeof rawContentType === "string" ? rawContentType : "application/td+json";

resolve(new Content(contentType, Readable.from(res.payload)));
});
req.on("error", (err: Error) => reject(err));
Expand Down
90 changes: 37 additions & 53 deletions packages/binding-coap/src/coap-server.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -41,7 +41,7 @@ const { debug, warn, info, error } = createLoggers("binding-coap", "coap-server"

type CoreLinkFormatParameters = Map<string, string[] | number[]>;

type AffordanceElement = PropertyElement | ActionElement | EventElement;
type AffordanceElement = Omit<PropertyElement, "forms"> | Omit<ActionElement, "forms"> | Omit<EventElement, "forms">;

// TODO: Move to core?
type AugmentedInteractionOptions = WoT.InteractionOptions & { formIndex: number };
Expand Down Expand Up @@ -145,11 +145,6 @@ export default class CoapServer implements ProtocolServer {
const port = this.getPort();
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Copilot AI Feb 15, 2026

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expose() now proceeds even when getPort() returns -1 (server not listening). That will generate invalid coap://...:-1/... URLs and register mDNS with an invalid port. Consider restoring the guard (warn + return) or throwing a clear error when port === -1 to prevent exposing before start() completes.

Suggested change
const port = this.getPort();
const port = this.getPort();
if (port === -1) {
warn(
`CoapServer expose() called for '${thing.title}' but server is not listening (port -1). ` +
"Did you forget to call start()?"
);
return;
}

Copilot uses AI. Check for mistakes.
const urlPath = this.createThingUrlPath(thing);

if (port === -1) {
warn("CoapServer is assigned an invalid port, aborting expose process.");
return;
}

this.fillInBindingData(thing, port, urlPath);

debug(`CoapServer on port ${port} exposes '${thing.title}' as unique '/${urlPath}'`);
Expand Down Expand Up @@ -236,12 +231,8 @@ export default class CoapServer implements ProtocolServer {
}

private addFormToAffordance(form: Form, affordance: AffordanceElement): void {
const affordanceForms = affordance.forms;
if (affordanceForms == null) {
affordance.forms = [form];
} else {
affordanceForms.push(form);
}
const withForms = affordance as AffordanceElement & { forms?: Form[] };
(withForms.forms ??= []).push(form);
}

private fillInPropertyBindingData(thing: ExposedThing, base: string, offeredMediaType: string) {
Expand Down Expand Up @@ -354,9 +345,8 @@ export default class CoapServer implements ProtocolServer {

public async destroy(thingId: string): Promise<boolean> {
debug(`CoapServer on port ${this.getPort()} destroying thingId '${thingId}'`);
for (const name of this.things.keys()) {
const exposedThing = this.things.get(name);
if (exposedThing?.id === thingId) {
for (const [name, exposedThing] of this.things.entries()) {
if (exposedThing.id === thingId) {
this.things.delete(name);
this.coreResources.delete(name);
this.mdnsIntroducer?.delete(name);
Expand All @@ -374,7 +364,7 @@ export default class CoapServer implements ProtocolServer {
return Array.from(this.coreResources.values())
.map((resource) => {
const formattedPath = `</${resource.urlPath}>`;
const parameters = Array.from(resource.parameters?.entries() ?? []);
const parameters = resource.parameters ? Array.from(resource.parameters.entries()) : [];

const parameterValues = parameters.map((parameter) => {
const key = parameter[0];
Expand Down Expand Up @@ -499,20 +489,24 @@ export default class CoapServer implements ProtocolServer {
const { thingKey, affordanceType, affordanceKey } = this.parseUriSegments(requestUri);
const thing = this.things.get(thingKey);

if (thing == null) {
if (thing === undefined) {
this.sendNotFoundResponse(res);
return;
}

// TODO: Remove support for trailing slashes (or rather: trailing empty URI path segments)
if (affordanceType == null || affordanceType === "") {
if (!affordanceType) {
await this.handleTdRequest(req, res, thing);
return;
}

switch (affordanceType) {
case this.PROPERTY_DIR:
this.handlePropertyRequest(thing, affordanceKey, req, res, contentType);
if (!affordanceKey) {
this.handlePropertiesRequest(req, contentType, thing, res);
} else {
this.handlePropertyRequest(thing, affordanceKey, req, res, contentType);
}
break;
case this.ACTION_DIR:
this.handleActionRequest(thing, affordanceKey, req, res, contentType);
Expand Down Expand Up @@ -554,11 +548,6 @@ export default class CoapServer implements ProtocolServer {
) {
const property = thing.properties[affordanceKey];

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thing.properties[affordanceKey] can be undefined for unknown property names, but the method now passes it straight into handleReadProperty/handleWriteProperty and later reads property.readOnly, which will throw. Add a not-found handling branch when property is undefined (likely a 4.04), instead of continuing.

Suggested change
if (!property) {
this.sendResponse(res, "4.04", "Property not found");
return;
}

Copilot uses AI. Check for mistakes.
if (property == null) {
this.handlePropertiesRequest(req, contentType, thing, res);
return;
}

switch (req.method) {
case "GET":
if (req.headers.Observe == null) {
Expand Down Expand Up @@ -588,7 +577,7 @@ export default class CoapServer implements ProtocolServer {
) {
const forms = thing.forms;

if (forms == null) {
if (!forms || forms.length === 0) {
this.sendNotFoundResponse(res);
return;
}
Expand Down Expand Up @@ -618,26 +607,30 @@ export default class CoapServer implements ProtocolServer {
contentType,
thing.uriVariables
);
const readablePropertyKeys = this.getReadableProperties(thing).map(([key, _]) => key);

const readablePropertyKeys = this.getReadableProperties(thing).map(([key]) => key);

const contentMap = await thing.handleReadMultipleProperties(readablePropertyKeys, interactionOptions);

const recordResponse: Record<string, DataSchemaValue> = {};
for (const [key, content] of contentMap.entries()) {
const value = ContentSerdes.get().contentToValue(
{ type: ContentSerdes.DEFAULT, body: await content.toBuffer() },
{}
);

if (value == null) {
// TODO: How should this case be handled?
try {
if (content.type !== ContentSerdes.DEFAULT && content.type !== "application/json") {
continue;
}
const buffer = await content.toBuffer();
const parsed = JSON.parse(buffer.toString());

recordResponse[key] = parsed;
} catch {
// Ignore non-JSON properties
Comment on lines +622 to +626
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Using JSON.parse here changes behavior compared to ContentSerdes.contentToValue/JsonCodec: it will throw on non-JSON payloads (e.g. plain strings without quotes) and the catch block then drops that property entirely. This breaks the prior relaxed decoding behavior (and will omit string-valued properties encoded as non-JSON). Consider switching back to ContentSerdes.get().contentToValue({ type: content.type, body: buffer }, /* schema */ ...) so decoding is consistent with the rest of the stack.

Suggested change
const parsed = JSON.parse(buffer.toString());
recordResponse[key] = parsed;
} catch {
// Ignore non-JSON properties
const parsed = ContentSerdes.get().contentToValue(
{ type: content.type, body: buffer },
undefined
);
recordResponse[key] = parsed;
} catch {
// Ignore non-JSON properties or decoding errors

Copilot uses AI. Check for mistakes.
continue;
}

recordResponse[key] = value;
}

const content = ContentSerdes.get().valueToContent(recordResponse, undefined, contentType);
this.streamContentResponse(res, content);
const responseContent = ContentSerdes.get().valueToContent(recordResponse, undefined, contentType);

this.streamContentResponse(res, responseContent);
} catch (err) {
const errorMessage = `${err}`;
error(`CoapServer on port ${this.getPort()} got internal error on read '${req.url}': ${errorMessage}`);
Expand Down Expand Up @@ -775,11 +768,6 @@ export default class CoapServer implements ProtocolServer {
) {
const action = thing.actions[affordanceKey];

if (action == null) {
this.sendNotFoundResponse(res);
return;
}

if (req.method !== "POST") {
this.sendMethodNotAllowedResponse(res);
return;
Comment on lines 769 to 773
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action can be undefined when an unknown action name (or missing segment) is requested, but handleActionRequest later dereferences action.forms / action.uriVariables unconditionally. Please add/restore a not-found guard (e.g., 4.04) when action is undefined to avoid runtime exceptions.

Copilot uses AI. Check for mistakes.
Expand Down Expand Up @@ -837,19 +825,14 @@ export default class CoapServer implements ProtocolServer {
) {
const event = thing.events[affordanceKey];

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event can be undefined when an unknown event name (or missing segment) is requested, but the code later dereferences event.forms / event.uriVariables unconditionally. Please add/restore a not-found guard (4.04) when event is undefined to prevent runtime exceptions.

Suggested change
if (!event) {
debug(
`CoapServer on port ${this.getPort()} received request for unknown event '${affordanceKey}' from ${Helpers.toUriLiteral(
req.rsinfo.address
)}:${req.rsinfo.port}`
);
this.sendResponse(res, "4.04", "Not Found");
return;
}

Copilot uses AI. Check for mistakes.
if (event == null) {
this.sendNotFoundResponse(res);
return;
}

if (req.method !== "GET") {
this.sendMethodNotAllowedResponse(res);
return;
}

const observe = req.headers.Observe as number;
const observe = req.headers.Observe as number | undefined;

if (observe == null) {
if (observe === undefined) {
debug(
`CoapServer on port ${this.getPort()} rejects '${affordanceKey}' event subscription from ${Helpers.toUriLiteral(
req.rsinfo.address
Expand Down Expand Up @@ -923,17 +906,18 @@ export default class CoapServer implements ProtocolServer {
}

private getContentTypeFromRequest(req: IncomingMessage): string {
const contentType = req.headers["Content-Format"] as string;
const contentType = req.headers["Content-Format"] as string | undefined;

if (contentType == null) {
if (contentType === undefined) {
warn(
`CoapServer on port ${this.getPort()} received no Content-Format from ${Helpers.toUriLiteral(
req.rsinfo.address
)}:${req.rsinfo.port}`
);
return ContentSerdes.DEFAULT;
}

return contentType ?? ContentSerdes.DEFAULT;
return contentType;
}

private checkContentTypeSupportForInput(method: string, contentType: string): boolean {
Expand Down Expand Up @@ -974,7 +958,7 @@ export default class CoapServer implements ProtocolServer {
}

// TODO: The name of this method might not be ideal yet.
private streamContentResponse(res: OutgoingMessage, content: Content, options?: { end?: boolean | undefined }) {
private streamContentResponse(res: OutgoingMessage, content: Content, options?: { end?: boolean }) {
res.setOption("Content-Format", content.type);
res.code = "2.05";
content.body.pipe(res, options);
Expand Down
10 changes: 5 additions & 5 deletions packages/binding-coap/src/coaps-client.ts
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Expand Up @@ -110,13 +110,13 @@ export default class CoapsClient implements ProtocolClient {
): Promise<Subscription> {
return new Promise<Subscription>((resolve, reject) => {
const requestUri = new URL(form.href.replace(/$coaps/, "https"));
if (this.authorization != null) {
if (this.authorization !== undefined) {
coaps.setSecurityParams(requestUri.hostname, this.authorization);
}

const callback = (resp: CoapResponse) => {
if (resp.payload != null) {
next(new Content(form?.contentType ?? ContentSerdes.DEFAULT, Readable.from(resp.payload)));
next(new Content(form.contentType ?? ContentSerdes.DEFAULT, Readable.from(resp.payload)));
}
};

Expand Down Expand Up @@ -163,14 +163,14 @@ export default class CoapsClient implements ProtocolClient {
}

public setSecurity(metadata: Array<SecurityScheme>, credentials?: pskSecurityParameters): boolean {
if (metadata === undefined || !Array.isArray(metadata) || metadata.length === 0) {
if (!Array.isArray(metadata) || metadata.length === 0) {
warn(`CoapsClient received empty security metadata`);
return false;
}

const security: SecurityScheme = metadata[0];

if (security.scheme === "psk" && credentials != null) {
if (security.scheme === "psk" && credentials !== undefined) {
this.authorization = { psk: {} };
this.authorization.psk[credentials.identity] = credentials.psk;
} else if (security.scheme === "apikey") {
Comment on lines +173 to 176
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credentials is typed as pskSecurityParameters (currently an index-signature map), but it is used as if it had { identity: string; psk: string } properties (credentials.identity / credentials.psk). This is inconsistent with the typing and can lead to incorrect usage by callers; consider updating the pskSecurityParameters type (or adjusting the code) so the type matches the actual expected shape.

Copilot uses AI. Check for mistakes.
Expand Down Expand Up @@ -224,7 +224,7 @@ export default class CoapsClient implements ProtocolClient {
): Promise<CoapResponse> {
// url only works with http*
const requestUri = new URL(form.href.replace(/$coaps/, "https"));
if (this.authorization != null) {
if (this.authorization !== undefined) {
coaps.setSecurityParams(requestUri.hostname, this.authorization);
}

Expand Down
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