Check

Summary

./godelw check runs a set of static analysis checks on the project Go files.

Tutorial start state

${GOPATH}/src/${PROJECT_PATH} exists, is the working directory and is initialized as a Git repository and Go module
Project contains godel and godelw
Project contains main.go
Project contains .gitignore that ignores GoLand files
Project contains echo/echo.go

Run checks

When writing Go code, it can be useful to check code for errors and consistency issues using static code analysis.

The current echo program simply echoes the user's input exactly. We will extend the program to allow different types of echoes to be generated. As a first step to doing this, we will define an Echoer interface that defines an Echo function and refactor the current echo functionality to be a simple echoer that implements this interface.

Run the following to update the program to perform this refactor:

➜ echo 'package echo

type Echoer interface {
	Echo(in string) string
}' > echo/echoer.go
➜ echo 'package echo

func NewEchoer() Echoer {
	return &simpleEchoer{}
}

type simpleEchoer struct{}

func (_ *simpleEchoer) Echo(in string) string {
	return in
}' > echo/echo.go
➜ SRC='package main

import (
	"fmt"
	"os"
	"strings"

	"PROJECT_PATH/echo"
)

func main() {
	echoer := echo.NewEchoer()
	fmt.Println(echoer.Echo(strings.Join(os.Args[1:], " ")))
}' && SRC=${SRC//PROJECT_PATH/$PROJECT_PATH} && echo "$SRC" > main.go

These files are formatted correctly and form a fully functioning program. Run ./godelw check to run static code checks on the project:

➜ ./godelw check
[compiles]      Running compiles...
[importalias]   Running importalias...
[errcheck]      Running errcheck...
[golint]        Running golint...
[deadcode]      Running deadcode...
[govet]         Running govet...
[importalias]   Finished importalias
[ineffassign]   Running ineffassign...
[golint]        echo/echo.go:9:1: receiver name should not be an underscore, omit the name if it is unused
[golint]        Finished golint
[outparamcheck] Running outparamcheck...
[ineffassign]   Finished ineffassign
[unconvert]     Running unconvert...
[deadcode]      Finished deadcode
[varcheck]      Running varcheck...
[unconvert]     Finished unconvert
[varcheck]      Finished varcheck
[outparamcheck] Finished outparamcheck
[compiles]      Finished compiles
[errcheck]      Finished errcheck
[govet]         Finished govet
Check(s) produced output: [golint]

The output indicates that there was an issue identified by the golint check. Fix the issue by updating the receiver name:

➜ echo 'package echo

func NewEchoer() Echoer {
	return &simpleEchoer{}
}

type simpleEchoer struct{}

func (e *simpleEchoer) Echo(in string) string {
	return in
}' > echo/echo.go

Run ./godelw check again to verify that the issue has been resolved:

➜ ./godelw check
[govet]         Running govet...
[compiles]      Running compiles...
[deadcode]      Running deadcode...
[importalias]   Running importalias...
[golint]        Running golint...
[errcheck]      Running errcheck...
[importalias]   Finished importalias
[ineffassign]   Running ineffassign...
[ineffassign]   Finished ineffassign
[outparamcheck] Running outparamcheck...
[golint]        Finished golint
[unconvert]     Running unconvert...
[govet]         Finished govet
[deadcode]      Finished deadcode
[varcheck]      Running varcheck...
[unconvert]     Finished unconvert
[varcheck]      Finished varcheck
[compiles]      Finished compiles
[errcheck]      Finished errcheck
[outparamcheck] Finished outparamcheck

Commit the changes to the repository:

➜ git add main.go echo
➜ git commit -m "Add echoer interface"
[master b931784] Add echoer interface
 3 files changed, 14 insertions(+), 2 deletions(-)
 create mode 100644 echo/echoer.go

Refer to the "More" sections below for examples of configuring the checks in different ways.

Tutorial end state

${GOPATH}/src/${PROJECT_PATH} exists, is the working directory and is initialized as a Git repository and Go module
Project contains godel and godelw
Project contains main.go
Project contains .gitignore that ignores GoLand files
Project contains echo/echo.go and echo/echoer.go

Tutorial next step

Run tests

More

Suppress check issues based on output

In some instances, it may be desirable to suppress certain issues flagged by checks. As an example, modify echo/echoer.go as follows:

➜ echo 'package echo

// Echoes the input.
type Echoer interface {
	Echo(in string) string
}' > echo/echoer.go

Running ./godelw check flags the following:

➜ ./godelw check
[compiles]      Running compiles...
[importalias]   Running importalias...
[deadcode]      Running deadcode...
[golint]        Running golint...
[errcheck]      Running errcheck...
[govet]         Running govet...
[importalias]   Finished importalias
[ineffassign]   Running ineffassign...
[ineffassign]   Finished ineffassign
[golint]        echo/echoer.go:3:1: comment on exported type Echoer should be of the form "Echoer ..." (with optional leading article)
[golint]        Finished golint
[outparamcheck] Running outparamcheck...
[unconvert]     Running unconvert...
[govet]         Finished govet
[deadcode]      Finished deadcode
[varcheck]      Running varcheck...
[unconvert]     Finished unconvert
[varcheck]      Finished varcheck
[outparamcheck] Finished outparamcheck
[compiles]      Finished compiles
[errcheck]      Finished errcheck
Check(s) produced output: [golint]

Although this is a valid check performed by go lint, not all projects conform exactly with the Go style for comments. In some cases, it makes sense to disable specific checks like this. This can be done by updating the godel/config/check.yml file to configure the check command to ignore all output from the golint check that contains comment on exported type \w should be of the form in its message.

The default configuration for godel/config/check-plugin.yml is as follows:

➜ cat godel/config/check-plugin.yml
checks:
  golint:
    filters:
      - value: "should have comment or be unexported"
      - value: "or a comment on this block"

Add the line - value: "comment on exported type [[:word:]]+ should be of the form" to this configuration:

➜ echo 'checks:
  golint:
    filters:
      - value: "should have comment or be unexported"
      - value: "or a comment on this block"
      - value: "comment on exported type [[:word:]]+ should be of the form"' > godel/config/check-plugin.yml

Re-run ./godelw check with the updated configuration to verify that lines that match this output are no longer reported:

➜ ./godelw check
[importalias]   Running importalias...
[compiles]      Running compiles...
[golint]        Running golint...
[govet]         Running govet...
[errcheck]      Running errcheck...
[deadcode]      Running deadcode...
[importalias]   Finished importalias
[ineffassign]   Running ineffassign...
[ineffassign]   Finished ineffassign
[golint]        Finished golint
[outparamcheck] Running outparamcheck...
[unconvert]     Running unconvert...
[deadcode]      Finished deadcode
[govet]         Finished govet
[varcheck]      Running varcheck...
[unconvert]     Finished unconvert
[varcheck]      Finished varcheck
[compiles]      Finished compiles
[outparamcheck] Finished outparamcheck
[errcheck]      Finished errcheck

Revert the local changes by running the following:

➜ git checkout -- echo godel

Filters have a type and a value. When type is not specified (as in the examples above), it defaults to message, which means that the value is matched against the message of the output. Currently, message is the only filter.

Exclude specific file names or paths from a check

Checks have an optional exclude field that can be used to specify names or paths of files that should be excluded from the check.

For example, the following configuration will ignore all issues reported by errcheck for main.go:

checks:
  errcheck:
    exclude:
      paths:
        - main.go

Because the exclude type is path, this configuration would ignore errcheck issues in ./main.go. However, issues in other files named main.go in the project (for example, ./subproject/main.go) would still be reported. Setting the exclude type to names would change the behavior so that issues in all files named main.go would be ignored. Both names and paths can be specified in the same exclude configuration.

The name match values use Go regular expressions to perform matches. For example, the following configuration ignores all golint issues reported for any files that have the extension .pb.go:

checks:
  golint:
    exclude:
      names:
        - ".*.pb.go"

The checks configuration also supports specifying exclude as a top-level value that applies to all checks (rather than just an individual one).

Disable checks

Checks can be disabled completely for the entire project by setting the skip field to true.

For example, the following configuration will disable the golint check for the project:

➜ echo 'checks:
  golint:
    skip: true' > godel/config/check-plugin.yml

Run ./godelw check with the updated configuration to verify that the golint check is no longer run:

➜ ./godelw check
[compiles]      Running compiles...
[importalias]   Running importalias...
[ineffassign]   Running ineffassign...
[errcheck]      Running errcheck...
[govet]         Running govet...
[deadcode]      Running deadcode...
[ineffassign]   Finished ineffassign
[importalias]   Finished importalias
[outparamcheck] Running outparamcheck...
[unconvert]     Running unconvert...
[deadcode]      Finished deadcode
[varcheck]      Running varcheck...
[govet]         Finished govet
[unconvert]     Finished unconvert
[varcheck]      Finished varcheck
[outparamcheck] Finished outparamcheck
[errcheck]      Finished errcheck
[compiles]      Finished compiles

Revert the local changes by running the following:

➜ git checkout -- godel

Configure checks

Many checks offer customizable parameters for the checks. Such parameters are specified in the config field of the check's configuration. Refer to the documentation for the asset that provides the check for details on configuring a check.

Run individual checks

Individual checks can be run in isolation by specifying the name of the check as an argument to check. This can be useful when iterating on code in an attempt to fix an issue flagged by a specific check.

For example, the following runs only deadcode and govet:

➜ ./godelw check deadcode govet
[govet]    Running govet...
[deadcode] Running deadcode...
[deadcode] Finished deadcode
[govet]    Finished govet

Run an underlying check directly

Running an individual check using check runs just that check, but it still runs it through the check task, which uses the logic of the plugin and the asset to determine the arguments passed to the underlying check. However, sometimes we may want to run the underlying check directly -- possibly to run it on a specific file or package or to specify flags that are not available through configuration.

The run-check task can be used to do this. Running ./godelw run-check [check] [flags] [args] calls the "underlying" check directly. It is up to an asset to determine what this means, but most assets wrap a standalone check implemented as its own CLI, and "running" the check means invoking the CLI. If the underlying check accepts flags, it is safest to place a -- after the check so that all of the flags and arguments are passed directly to the underlying check.

For example, errcheck can be invoked directly as follows:

➜ ./godelw run-check errcheck -- --help
Usage of /root/.godel/assets/com.palantir.godel-okgo-asset-errcheck-errcheck-asset-1.8.0:
  -abspath
    	print absolute paths to files
  -asserts
    	if true, check for ignored type assertion results
  -blank
    	if true, check for errors assigned to blank identifier
  -exclude string
    	Path to a file containing a list of functions to exclude from checking
  -ignore value
    	[deprecated] comma-separated list of pairs of the form pkg:regex
    	            the regex is used to ignore names within pkg.
  -ignoregenerated
    	if true, checking of files with generated code is disabled
  -ignorepkg string
    	comma-separated list of package paths to ignore
  -ignoretests
    	if true, checking of _test.go files is disabled
  -tags value
    	space-separated list of build tags to include
  -verbose
    	produce more verbose logging

The help output printed here is that of errcheck, and we could have supplied the errcheck flags and arguments directly in place of --help. Also note the use of -- to indicate that all of the flags/arguments should be passed to the underlying command. In this instance, if -- was not used, the --help flag would have shown the output for run-check errcheck instead:

➜ ./godelw run-check errcheck --help
Usage:
  okgo run-check errcheck [flags]

Flags:
  -h, --help   help for errcheck

Global Flags:
      --assets strings        path(s) to the plugin asset(s)
      --config string         path to the plugin configuration file
      --debug                 run in debug mode
      --godel-config string   path to the godel.yml configuration file
      --project-dir string    path to project directory

Run checks sequentially

Checks can be run sequentially by running with the --parallel=false flag:

➜ ./godelw check --parallel=false
Running compiles...
Finished compiles
Running deadcode...
Finished deadcode
Running errcheck...
Finished errcheck
Running golint...
Finished golint
Running govet...
Finished govet
Running importalias...
Finished importalias
Running ineffassign...
Finished ineffassign
Running outparamcheck...
Finished outparamcheck
Running unconvert...
Finished unconvert
Running varcheck...
Finished varcheck

Constituent checks

gödel includes the following checks by default:

compiles verifies that all of the Go code in the project compiles, including code in test files (which is not checked by go build)
deadcode finds unused code
errcheck ensures that returned errors are checked
extimport verifies that all non-standard library packages that are imported by the project are present in a vendor directory within the project
govet runs go vet
importalias ensures that, if an import path in the package is imported using an alias, then all imports in the project that assign an alias for that path use the same alias
ineffassign flags ineffectual assignment statements
novendor flags projects that exist in the vendor directory but are not used by the project
outparamcheck checks that functions that are meant to take an output parameter defined as an interface{} are passed pointers to an object rather than a concrete object
unconvert flags unnecessary conversions
varcheck checks for unused global variables and constants

Add or remove checks

The checks that are available to the check task are determined by the assets provided to the okgo plugin. Checks can be added or removed by modifying the asset configuration for the okgo plugin.

For example, we can add the nobadfuncs check by adding the godel-okgo-asset-nobadfuncs asset. Modify the godel/config/godel.yml file as follows:

➜ echo 'default-tasks:
  resolvers:
    - https://github.com/{{index GroupParts 1}}/{{index GroupParts 2}}/releases/download/v{{Version}}/{{Product}}-{{Version}}-{{OS}}-{{Arch}}.tgz
  tasks:
    com.palantir.okgo:check-plugin:
      assets:
        - locator:
            id: "com.palantir.godel-okgo-asset-nobadfuncs:nobadfuncs-asset:1.5.0"
exclude:
  names:
    - "\\\\..+"
    - "vendor"
  paths:
    - "godel"' > godel/config/godel.yml

This adds the asset, which makes it available as a check:

➜ ./godelw check nobadfuncs
Getting package from https://github.com/palantir/godel-okgo-asset-nobadfuncs/releases/download/v1.5.0/nobadfuncs-asset-1.5.0-linux-amd64.tgz...

221.18 KiB / 4.76 MiB [-->_____________________________________________________________] 4.54% ? p/s
1.65 MiB / 4.76 MiB [---------------------->__________________________________________] 34.69% ? p/s
3.70 MiB / 4.76 MiB [-------------------------------------------------->______________] 77.70% ? p/s
4.76 MiB / 4.76 MiB [---------------------------------------------------------] 100.00% 9.23 MiB p/s
Running nobadfuncs...
Finished nobadfuncs

Although the skip configuration makes it easy to disable a check, it is also possible to remove the check entirely. This can be done by updating the exclude-default-assets configuration. For example, the following configuration removes the novendor check entirely:

➜ echo 'default-tasks:
  resolvers:
    - https://github.com/{{index GroupParts 1}}/{{index GroupParts 2}}/releases/download/v{{Version}}/{{Product}}-{{Version}}-{{OS}}-{{Arch}}.tgz
  tasks:
    com.palantir.okgo:check-plugin:
      exclude-default-assets:
        - "com.palantir.godel-okgo-asset-novendor:novendor-asset"
exclude:
  names:
    - "\\\\..+"
    - "vendor"
  paths:
    - "godel"' > godel/config/godel.yml

Verify that novendor is no longer present as a check:

➜ ./godelw check novendor
Error: provided checker type(s) [novendor] not valid: valid values are [compiles deadcode errcheck golint govet importalias ineffassign outparamcheck unconvert varcheck]

Revert the local changes by running the following:

➜ git checkout -- godel

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Check

Summary

Tutorial start state

Run checks

Tutorial end state

Tutorial next step

More

Suppress check issues based on output

Exclude specific file names or paths from a check

Disable checks

Configure checks

Run individual checks

Run an underlying check directly

Run checks sequentially

Constituent checks

Add or remove checks

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