No overload matches this call. Type 'string' is not assignable to type 'Signals'
Javascriptnode.jsTypescriptSignalsJavascript Problem Overview
I am using typescript to build a microservice and handling signals as well. The code was working fine till a few days ago but recently it started throwing errors. Couldn't find a fix for the issue.
code for handling signals. It is just part of the file.
src/main.ts
enum signals {
SIGHUP = 1,
SIGINT = 2,
SIGTERM = 15
}
const shutdown = (signal, value) => {
logger.warn("shutdown!")
Db.closeAll()
process.exit(value)
}
Object.values(signals).forEach(signal => {
process.on(signal, () => {
logger.warn(`process received a ${signal} signal`)
shutdown(signal, signals[signal])
})
})
When I do ts-node src/main.ts
The following error throws and exits.
/home/meraj/.nvm/versions/node/v8.10.0/lib/node_modules/ts-node/src/index.ts:245
return new TSError(diagnosticText, diagnosticCodes)
^
TSError: ⨯ Unable to compile TypeScript:
src/main.ts:35:16 - error TS2769: No overload matches this call.
The last overload gave the following error.
Argument of type 'string | signals' is not assignable to parameter of type 'Signals'.
Type 'string' is not assignable to type 'Signals'.
35 process.on(signal, () => {
~~~~~~
node_modules/@types/node/base.d.ts:653:9
653 on(event: Signals, listener: SignalsListener): this;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The last overload is declared here.
at createTSError (/home/meraj/.nvm/versions/node/v8.10.0/lib/node_modules/ts-node/src/index.ts:245:12)
at reportTSError (/home/meraj/.nvm/versions/node/v8.10.0/lib/node_modules/ts-node/src/index.ts:249:19)
at getOutput (/home/meraj/.nvm/versions/node/v8.10.0/lib/node_modules/ts-node/src/index.ts:362:34)
at Object.compile (/home/meraj/.nvm/versions/node/v8.10.0/lib/node_modules/ts-node/src/index.ts:395:32)
at Module.m._compile (/home/meraj/.nvm/versions/node/v8.10.0/lib/node_modules/ts-node/src/index.ts:473:43)
at Module._extensions..js (module.js:663:10)
at Object.require.extensions.(anonymous function) [as .ts] (/home/meraj/.nvm/versions/node/v8.10.0/lib/node_modules/ts-node/src/index.ts:476:12)
at Module.load (module.js:565:32)
at tryModuleLoad (module.js:505:12)
at Function.Module._load (module.js:497:3)
Any fix would be appreciated. Or If you can tell why it was working earlier just 2 days ago and not now.
Javascript Solutions
Solution 1 - Javascript
This sometimes happens when you have passed an incorrect number of arguments to an anonymous function:
Object.keys(data).reduce((key: string) => {
}, {});
will raise error:
> No overload matches this call. Overload 1 of 3
Pass it the correct number of arguments:
Object.keys(data).reduce((acc: any, key: string) => {
}, {});
Solution 2 - Javascript
I also had this strange issue, but I worked around it using type assertions (in my case using a string enum):
(Object.values(someEnum) as string[]).concat(otherStringArray);
Solution 3 - Javascript
numeric enum signals
Solution 1: Keep Object.values(signals)
// numeric enum includes reverse mapping, filter numbers out and keep "SIGHUP" etc.
.filter((s): s is NodeJS.Signals => typeof s !== "number")
.forEach(signal => {
process.on(signal, ...) // works now
})
Solution 2: Use pure signal string literal types
// these string literal items are strongly typed by built-in NodeJS.Signals type
Object.values<NodeJS.Signals>(["SIGHUP", "SIGINT", "SIGTERM"])
.forEach(signal => {
process.on(signal, ...) // works now
})
string enum (no reverse mapping)
Solution 3: Change toenum signals2 {
SIGHUP = "SIGHUP",
SIGINT = "SIGINT",
SIGTERM = "SIGTERM"
}
Object.values(signals2)
.forEach(signal => {
process.on(signal, ...) // works now
})
Why does the error happen?
Numeric enums like signals
include a reverse mapping. For example you can do the following:
const r1 = signals.SIGHUP // r1 value: 1
const r2 = signals[signals.SIGINT] // r2 value: "SIGINT"
const r3 = signals[15] // r3 value: "SIGTERM"
That is why you get (string | signals)[]
back for Object.values(signals)
, where string
stands for the enum keys and signals
for the enum values.
Now, parameter signal
in process.on(signal, ...)
must be one of the predefined Node.JS string literal types. However we pass in string | signals
item type, so TS yells at this point.
Solution 4 - Javascript
This happens when you do not assign your types properly.
Your variable data Type MUST match the passing data type.
organizationList: { id: string; name: string; }[] = [] //if you do this way it type error
organizationList: Organization[] = [] //correct defining method
get Org() {
return this.list.filter((org: Organization) => org.id == this.id) //this data type must defined data type
}