commands: add an alias for --check to be the same as --call=check

This adds an alias for `--check` that causes it to behave the same as
`--call=check`. This is done using `BoolFunc` to call a function when
the option is seen and to set it to the correct value. This should allow
command line flags like `--check --call=targets` to work correctly (even
though they conflict) by making it so the first invocation sets the
print function to `check` and the second overwrites the first. This is
the expected behavior for these types of boolean flags.

`BoolFunc` itself is part of the standard library flags package, but
never seems to have made it into pflag possibly because it was added in
go 1.21.

https://pkg.go.dev/flag#FlagSet.BoolFunc

Signed-off-by: Jonathan A. Sternberg <jonathan.sternberg@docker.com>

commands/build.go

@@ -629,6 +629,8 @@ func buildCmd(dockerCli command.Cli, rootOpts *rootOptions, debugConfig *debug.D
 	}
 
 	flags.StringVar(&options.printFunc, "call", "build", `Set method for evaluating build ("check", "outline", "targets")`)
+	flags.VarPF(callAlias(options, "check"), "check", "", `Shorthand for "--call=check"`)
+	flags.Lookup("check").NoOptDefVal = "true"
 
 	// hidden flags
 	var ignore string
@@ -1003,6 +1005,20 @@ func maybeJSONArray(v string) []string {
 	return []string{v}
 }
 
+func callAlias(options *buildOptions, value string) cobrautil.BoolFuncValue {
+	return func(s string) error {
+		v, err := strconv.ParseBool(s)
+		if err != nil {
+			return err
+		}
+
+		if v {
+			options.printFunc = value
+		}
+		return nil
+	}
+}
+
 // timeBuildCommand will start a timer for timing the build command. It records the time when the returned
 // function is invoked into a metric.
 func timeBuildCommand(mp metric.MeterProvider, attrs attribute.Set) func(err error) {

docs/reference/buildx_build.md

@@ -26,6 +26,7 @@ Start a build
 | [`--cache-to`](#cache-to)                                                                                                                          | `stringArray` |           | Cache export destinations (e.g., `user/app:cache`, `type=local,dest=path/to/dir`)                   |
 | `--call`                                                                                                                                           | `string`      | `build`   | Set method for evaluating build (`check`, `outline`, `targets`)                                     |
 | [`--cgroup-parent`](https://docs.docker.com/reference/cli/docker/image/build/#cgroup-parent)                                                       | `string`      |           | Set the parent cgroup for the `RUN` instructions during build                                       |
+| `--check`                                                                                                                                          |               |           | Shorthand for `--call=check`                                                                        |
 | `--detach`                                                                                                                                         |               |           | Detach buildx server (supported only on linux) (EXPERIMENTAL)                                       |
 | [`-f`](https://docs.docker.com/reference/cli/docker/image/build/#file), [`--file`](https://docs.docker.com/reference/cli/docker/image/build/#file) | `string`      |           | Name of the Dockerfile (default: `PATH/Dockerfile`)                                                 |
 | `--iidfile`                                                                                                                                        | `string`      |           | Write the image ID to a file                                                                        |

docs/reference/buildx_debug_build.md

@@ -22,6 +22,7 @@ Start a build
 | `--cache-to`                                                                                                                                       | `stringArray` |           | Cache export destinations (e.g., `user/app:cache`, `type=local,dest=path/to/dir`)                   |
 | `--call`                                                                                                                                           | `string`      | `build`   | Set method for evaluating build (`check`, `outline`, `targets`)                                     |
 | [`--cgroup-parent`](https://docs.docker.com/reference/cli/docker/image/build/#cgroup-parent)                                                       | `string`      |           | Set the parent cgroup for the `RUN` instructions during build                                       |
+| `--check`                                                                                                                                          |               |           | Shorthand for `--call=check`                                                                        |
 | `--detach`                                                                                                                                         |               |           | Detach buildx server (supported only on linux) (EXPERIMENTAL)                                       |
 | [`-f`](https://docs.docker.com/reference/cli/docker/image/build/#file), [`--file`](https://docs.docker.com/reference/cli/docker/image/build/#file) | `string`      |           | Name of the Dockerfile (default: `PATH/Dockerfile`)                                                 |
 | `--iidfile`                                                                                                                                        | `string`      |           | Write the image ID to a file                                                                        |

util/cobrautil/boolfunc.go

@@ -0,0 +1,11 @@
+package cobrautil
+
+type BoolFuncValue func(string) error
+
+func (f BoolFuncValue) Set(s string) error { return f(s) }
+
+func (f BoolFuncValue) String() string { return "" }
+
+func (f BoolFuncValue) Type() string { return "bool" }
+
+func (f BoolFuncValue) IsBoolFlag() bool { return true }