#
Logging

These are just a few simple logging utilities provided to simplify and standardize the error facilities across the Ethers library.

The Logger library has zero dependencies and is intentionally very light so it can be easily included in each library.

The Censorship functionality relies on one instance of the Ethers library being included. In large bundled packages or when `npm link` is used, this may not be the case. If you require this functionality, ensure that your bundling is configured properly.

##
Logger
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new ethers.utils.Logger( version )
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Create a new logger which will include version in all errors thrown.

Logger.globalLogger( ) ⇒ Logger
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Returns the singleton global logger.

###
Logging Output

logger.debug( ...args ) ⇒ void
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Log debugging information.

logger.info( ...args ) ⇒ void
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Log generic information.

logger.warn( ...args ) ⇒ void
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Log warnings.

###
Errors

These functions honor the current Censorship and help create a standard error model for detecting and processing errors within Ethers.

logger.makeError( message [ , code = UNKNOWN_ERROR [ , params ] ] ) ⇒ Error
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Create an Error object with message and an optional code and additional params set. This is useful when an error is needed to be rejected instead of thrown.

logger.throwError( message [ , code = UNKNOWN_ERROR [ , params ] ] ) ⇒ never
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Throw an Error with message and an optional code and additional params set.

logger.throwArgumentError( message , name , value ) ⇒ never
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Throw an INVALID_ARGUMENT Error with name and value.

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Usage Validation

There can be used to ensure various properties and actions are safe.

logger.checkAbstract( target , kind ) ⇒ void
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Checks that target is not kind and performs the same operatons as `checkNew`. This is useful for ensuring abstract classes are not being instantiated.

logger.checkArgumentCount( count , expectedCound [ , message ) ⇒ void
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If count is not equal to expectedCount, throws a MISSING_ARGUMENT or UNEXPECTED_ARGUMENT error.

logger.checkNew( target , kind ) ⇒ void
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If target is not a valid `this` or `target` value, throw a MISSING_NEW error. This is useful to ensure callers of a Class are using `new`.

logger.checkNormalize( message ) ⇒ void
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Check that the environment has a correctly functioning String.normalize. If not, a UNSUPPORTED_OPERATION error is thrown.

logger.checkSafeUint53( value [ , message ] ) ⇒ void
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If value is not safe as a JavaScript number, throws a NUMERIC_FAULT error.

###
Censorship

Logger.setCensorship( censor [ , permanent = false ] ) ⇒ void
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Set error censorship, optionally preventing errors from being uncensored.

In production applications, this prevents any error from leaking information by masking the message and values of errors.

This can impact debugging, making it substantially more difficult.

Logger.setLogLevel( logLevel ) ⇒ void
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Set the log level, to suppress logging output below a particular log level.

##
Errors

Every error in Ethers has a `code` value, which is a string that will match one of the following error codes.

###
Generic Error Codes

Logger.errors.NOT_IMPLEMENTED

The operation is not implemented.

Logger.errors.SERVER_ERROR

There was an error communicating with a server.

Logger.errors.TIMEOUT

A timeout occurred.

Logger.errors.UNKNOWN_ERROR

A generic unknown error.

Logger.errors.UNSUPPORTED_OPERATION

The operation is not supported.

###
Safety Error Codes

Logger.errors.BUFFER_OVERRUN

The amount of data needed is more than the amount of data required, which would cause the data buffer to read past its end.

Logger.errors.NUMERIC_FAULT

There was an invalid operation done on numeric values.

Common cases of this occur when there is overflow, arithmetic underflow in fixed numeric types or division by zero.

###
Usage Error Codes

Logger.errors.INVALID_ARGUMENT

The type or value of an argument is invalid. This will generally also include the `name` and `value` of the argument. Any function which accepts sensitive data (such as a private key) will include the string `[[REDACTED]]` instead of the value passed in.

Logger.errors.MISSING_ARGUMENT

An expected parameter was not specified.

Logger.errors.MISSING_NEW

An object is a Class, but is now being called with `new`.

Logger.errors.UNEXPECTED_ARGUMENT

Too many parameters we passed into a function.

###
Ethereum Error Codes

Logger.errors.CALL_EXCEPTION

An attempt to call a blockchain contract (getter) resulted in a revert or other error.

Logger.errors.INSUFFICIENT_FUNDS

The account is attempting to make a transaction which costs more than is available.

A sending account must have enough ether to pay for the value, the gas limit (at the gas price) as well as the intrinsic cost of data. The intrinsic cost of data is 4 gas for each zero byte and 68 gas for each non-zero byte.

Logger.errors.NETWORK_ERROR

An Ethereum network validation error, such as an invalid chain ID.

Logger.errors.NONCE_EXPIRED

The nonce being specified has already been used in a mined transaction.

Logger.errors.REPLACEMENT_UNDERPRICED

When replacing a transaction, by using a nonce which has already been sent to the network, but which has not been mined yet the new transaction must specify a higher gas price.

This error occurs when the gas price is insufficient to bribe the transaction pool to prefer the new transaction over the old one. Generally, the new gas price should be about 50% + 1 wei more, so if a gas price of 10 gwei was used, the replacement should be 15.000000001 gwei.

Logger.errors.UNPREDICTABLE_GAS_LIMIT

When estimating the required amount of gas for a transaction, a node is queried for its best guess.

If a node is unable (or unwilling) to predict the cost, this error occurs.

The best remedy for this situation is to specify a gas limit in the transaction manually.

This error can also indicate that the transaction is expected to fail regardless, if for example an account with no tokens is attempting to send a token.

##
Log Levels

Logger.levels.DEBUG

Log all output, including debugging information.

Logger.levels.INFO

Only log output for infomational, warnings and errors.

Logger.levels.WARNING

Only log output for warnings and errors.

Logger.levels.ERROR

Only log output for errors.

Logger.levels.OFF

Do not output any logs.

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