feat: Make Build Entrypoint configurable

VJftw · VJftw · commit 2a2caeea5627 · 2025-09-06T01:16:22.000+01:00
Adds optional `build_entrypoint` fields to the `build_rule` builtin to
enable us to use binaries directly when building and support other
cross-platform shells (e.g. nushell).
diff --git a/rules/builtins.build_defs b/rules/builtins.build_defs
@@ -2,18 +2,65 @@
 
 
 # Do not change the order of arguments to this function without updating the iota in targets.go to match it.
-def build_rule(name:str, cmd:str|dict='', test_cmd:str|dict='', debug_cmd:str='', srcs:list|dict=None, data:list|dict=None,
-               debug_data:list|dict=None, outs:list|dict=None, deps:list=None, exported_deps:list=None, secrets:list|dict=None,
-               tools:str|list|dict=None, test_tools:str|list|dict=None, debug_tools:str|list|dict=None, labels:list=None,
-               visibility:list=CONFIG.DEFAULT_VISIBILITY, hashes:list=None, binary:bool=False, test:bool=False,
-               test_only:bool=CONFIG.DEFAULT_TESTONLY, building_description:str=None, needs_transitive_deps:bool=False,
-               output_is_complete:bool=False, sandbox:bool=CONFIG.BUILD_SANDBOX, test_sandbox:bool=CONFIG.TEST_SANDBOX,
-               no_test_output:bool=False, flaky:bool|int=0, build_timeout:int|str=0, test_timeout:int|str=0, pre_build:function=None,
-               post_build:function=None, requires:list=None, provides:dict=None, licences:list=CONFIG.DEFAULT_LICENCES,
-               test_outputs:list=None, system_srcs:list=None, stamp:bool=False, tag:str='', optional_outs:list=None, progress:bool=False,
-               size:str=None, _urls:list=None, internal_deps:list=None, pass_env:list=None, local:bool=False, output_dirs:list=[],
-               exit_on_error:bool=CONFIG.EXIT_ON_ERROR, entry_points:dict={}, env:dict={}, _file_content:str=None,
-               _subrepo:bool=False, no_test_coverage:bool=False):
+def build_rule(
+        name:str,
+        cmd:str|dict="",
+        test_cmd:str|dict="",
+        debug_cmd:str="",
+        srcs:list|dict=None,
+        data:list|dict=None,
+        debug_data:list|dict=None,
+        outs:list|dict=None,
+        deps:list=None,
+        exported_deps:list=None,
+        secrets:list|dict=None,
+        tools:str|list|dict=None,
+        test_tools:str|list|dict=None,
+        debug_tools:str|list|dict=None,
+        labels:list=None,
+        visibility:list=CONFIG.DEFAULT_VISIBILITY,
+        hashes:list=None,
+        binary:bool=False,
+        test:bool=False,
+        test_only:bool=CONFIG.DEFAULT_TESTONLY,
+        building_description:str=None,
+        needs_transitive_deps:bool=False,
+        output_is_complete:bool=False,
+        sandbox:bool=CONFIG.BUILD_SANDBOX,
+        test_sandbox:bool=CONFIG.TEST_SANDBOX,
+        no_test_output:bool=False,
+        flaky:bool|int=0,
+        build_timeout:int|str=0,
+        test_timeout:int|str=0,
+        pre_build:function=None,
+        post_build:function=None,
+        requires:list=None,
+        provides:dict=None,
+        licences:list=CONFIG.DEFAULT_LICENCES,
+        test_outputs:list=None,
+        system_srcs:list=None,
+        stamp:bool=False,
+        tag:str="",
+        optional_outs:list=None,
+        progress:bool=False,
+        size:str=None,
+        _urls:list=None,
+        internal_deps:list=None,
+        pass_env:list=None,
+        local:bool=False,
+        output_dirs:list=[],
+        exit_on_error:bool=CONFIG.EXIT_ON_ERROR,
+        entry_points:dict={},
+        env:dict={},
+        _file_content:str=None,
+        _subrepo:bool=False,
+        no_test_coverage:bool=False,
+        # This matches the default `BuildEntrypoint` is defined in
+        #`src/core/build_entrypoint.go`.
+        build_entry_point:list=None,
+        build_entry_point_exit_on_error_args:list=None,
+        build_entry_point_interactive_args:list=None,
+        build_entry_point_exec_command_args:list=None):
     pass
 
 def chr(i:int) -> str:
diff --git a/src/build/build_step.go b/src/build/build_step.go
@@ -3,6 +3,7 @@ package build
 
 import (
 	"bytes"
+	"context"
 	"encoding/hex"
 	"errors"
 	"fmt"
@@ -515,12 +516,28 @@ func runBuildCommand(state *core.BuildState, target *core.BuildTarget, command s
 	if target.IsTextFile {
 		return nil, buildTextFile(state, target)
 	}
+
 	env := core.StampedBuildEnvironment(state, target, inputHash, filepath.Join(core.RepoRoot, target.TmpDir()), target.Stamp).ToSlice()
 	log.Debug("Building target %s\nENVIRONMENT:\n%s\n%s", target.Label, env, command)
-	out, combined, err := state.ProcessExecutor.ExecWithTimeoutShell(target, target.TmpDir(), env, target.BuildTimeout, state.ShowAllOutput, false, process.NewSandboxConfig(target.Sandbox, target.Sandbox), command)
+
+	buildArgvOpts := []core.BuildArgvOpt{target.BuildEntryPoint.WithBuildArgvCommand(command)}
+	if target.ShouldExitOnError() {
+		buildArgvOpts = append(buildArgvOpts, target.BuildEntryPoint.WithBuildArgvExitOnError())
+	}
+	argv, err := target.BuildEntryPoint.BuildArgv(state, target, buildArgvOpts...)
+	if err != nil {
+		return nil, err
+	}
+	out, combined, err := state.ProcessExecutor.ExecWithTimeout(
+		context.Background(),
+		target, target.TmpDir(), env, target.BuildTimeout, state.ShowAllOutput,
+		false, false, false, process.NewSandboxConfig(target.Sandbox, target.Sandbox),
+		argv,
+	)
 	if err != nil {
 		return nil, fmt.Errorf("Error building target %s: %s\n%s", target.Label, err, combined)
 	}
+
 	return out, nil
 }
 
diff --git a/src/build/incrementality_test.go b/src/build/incrementality_test.go
@@ -26,6 +26,7 @@ var KnownFields = map[string]bool{
 	"IsTextFile":                  true,
 	"FileContent":                 true,
 	"IsRemoteFile":                true,
+	"BuildEntryPoint":             true,
 	"Command":                     true,
 	"Commands":                    true,
 	"NeedsTransitiveDependencies": true,
diff --git a/src/core/build_entrypoint.go b/src/core/build_entrypoint.go
@@ -0,0 +1,96 @@
+package core
+
+type BuildEntrypoint struct {
+	Entrypoint      []string
+	ExecCommandArgs []string
+	ExitOnErrorArgs []string
+	InteractiveArgs []string
+}
+
+type BuildEntrypointOpt func(*BuildEntrypoint)
+
+func WithBuildEntrypointEntrypoint(entrypoint []string) BuildEntrypointOpt {
+	return func(be *BuildEntrypoint) {
+		be.Entrypoint = entrypoint
+	}
+}
+
+func WithBuildEntrypointExitOnErrorArgs(args []string) BuildEntrypointOpt {
+	return func(be *BuildEntrypoint) {
+		be.ExitOnErrorArgs = args
+	}
+}
+
+func WithBuildEntrypointExecCommandArgs(args []string) BuildEntrypointOpt {
+	return func(be *BuildEntrypoint) {
+		be.ExecCommandArgs = args
+	}
+}
+
+func WithBuildEntrypointInteractiveArgs(args []string) BuildEntrypointOpt {
+	return func(be *BuildEntrypoint) {
+		be.InteractiveArgs = args
+	}
+}
+
+func NewBuildEntrypoint(opts ...BuildEntrypointOpt) *BuildEntrypoint {
+	be := &BuildEntrypoint{
+		Entrypoint:      []string{},
+		ExecCommandArgs: []string{},
+		ExitOnErrorArgs: []string{},
+		InteractiveArgs: []string{},
+	}
+
+	for _, opt := range opts {
+		opt(be)
+	}
+
+	// Default to Bash if Entrypoint not set.
+	if len(be.Entrypoint) < 1 {
+		be.Entrypoint = []string{"bash", "--noprofile", "--norc", "-u", "-o", "pipefail"}
+		be.ExecCommandArgs = []string{"-c"}
+		be.ExitOnErrorArgs = []string{"-e"}
+		be.InteractiveArgs = []string{}
+	}
+
+	return be
+}
+
+type BuildArgv struct{ Argv []string }
+type BuildArgvOpt func(*BuildArgv)
+
+func (be *BuildEntrypoint) WithBuildArgvExitOnError() BuildArgvOpt {
+	return func(ba *BuildArgv) {
+		ba.Argv = append(ba.Argv, be.ExitOnErrorArgs...)
+	}
+}
+
+func (be *BuildEntrypoint) WithBuildArgvInteractive() BuildArgvOpt {
+	return func(ba *BuildArgv) {
+		log.Debugf("pre interactive argv: %#v", ba.Argv)
+		ba.Argv = append(ba.Argv, be.InteractiveArgs...)
+
+		log.Debugf("post interactive argv: %#v", ba.Argv)
+	}
+}
+
+func (be *BuildEntrypoint) WithBuildArgvCommand(command string) BuildArgvOpt {
+	return func(ba *BuildArgv) {
+		ba.Argv = append(ba.Argv, append(be.ExecCommandArgs, command)...)
+	}
+}
+
+func (be *BuildEntrypoint) BuildArgv(buildState *BuildState, target *BuildTarget, opts ...BuildArgvOpt) ([]string, error) {
+	argv := &BuildArgv{Argv: be.Entrypoint}
+	for _, opt := range opts {
+		opt(argv)
+	}
+
+	newArg0, err := ReplaceSequences(buildState, target, argv.Argv[0])
+	if err != nil {
+		return nil, err
+	}
+	argv.Argv[0] = newArg0
+
+	return argv.Argv, nil
+}
diff --git a/src/core/build_entrypoint_test.go b/src/core/build_entrypoint_test.go
@@ -0,0 +1,75 @@
+package core
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNewBuildEntrypoint(t *testing.T) {
+	var tests = []struct {
+		description string
+		opts        []BuildEntrypointOpt
+		expected    *BuildEntrypoint
+	}{
+		{
+			"DefaultConfigIsBash",
+			nil,
+			&BuildEntrypoint{
+				Entrypoint:      []string{"bash", "--noprofile", "--norc", "-u", "-o", "pipefail"},
+				ExecCommandArgs: []string{"-c"},
+				ExitOnErrorArgs: []string{"-e"},
+				InteractiveArgs: []string{},
+			},
+		},
+		{
+			"NuShell",
+			[]BuildEntrypointOpt{
+				WithBuildEntrypointEntrypoint([]string{"nu", "--no-config-file", "--no-history"}),
+				WithBuildEntrypointInteractiveArgs([]string{"--execute", "$env.config.show_banner = false"}),
+				WithBuildEntrypointExecCommandArgs([]string{"--commands"}),
+			},
+			&BuildEntrypoint{
+				Entrypoint:      []string{"nu", "--no-config-file", "--no-history"},
+				ExecCommandArgs: []string{"--commands"},
+				ExitOnErrorArgs: []string{},
+				InteractiveArgs: []string{"--execute", "$env.config.show_banner = false"},
+			},
+		},
+		{
+			"Powershell",
+			[]BuildEntrypointOpt{
+				WithBuildEntrypointEntrypoint([]string{"pwsh", "-NoProfile"}),
+				WithBuildEntrypointInteractiveArgs([]string{"-Interactive"}),
+				WithBuildEntrypointExecCommandArgs([]string{"-Command"}),
+			},
+			&BuildEntrypoint{
+				Entrypoint:      []string{"pwsh", "-NoProfile"},
+				ExecCommandArgs: []string{"-Command"},
+				ExitOnErrorArgs: []string{},
+				InteractiveArgs: []string{"-Interactive"},
+			},
+		},
+		{
+			"Elvish",
+			[]BuildEntrypointOpt{
+				WithBuildEntrypointEntrypoint([]string{"elvish", "-norc"}),
+				WithBuildEntrypointInteractiveArgs([]string{"-i"}),
+				WithBuildEntrypointExecCommandArgs([]string{"-c"}),
+			},
+			&BuildEntrypoint{
+				Entrypoint:      []string{"elvish", "-norc"},
+				ExecCommandArgs: []string{"-c"},
+				ExitOnErrorArgs: []string{},
+				InteractiveArgs: []string{"-i"},
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.description, func(t *testing.T) {
+			actualBec := NewBuildEntrypoint(tt.opts...)
+			assert.Equal(t, tt.expected, actualBec)
+		})
+	}
+}
diff --git a/src/core/build_target.go b/src/core/build_target.go
@@ -134,7 +134,9 @@ type BuildTarget struct {
 	OptionalOutputs []string `name:"optional_outs"`
 	// Optional labels applied to this rule. Used for including/excluding rules.
 	Labels []string
-	// Shell command to run.
+	// Build Entrypoint configuration.
+	BuildEntryPoint *BuildEntrypoint `name:"build_entry_point" hide:"filegroup"`
+	// Shell command to run, this is passed as the last argument to the Binary.
 	Command string `name:"cmd" hide:"filegroup"`
 	// Per-configuration shell commands to run.
 	Commands map[string]string `name:"cmd" hide:"filegroup"`
@@ -384,6 +386,7 @@ func NewBuildTarget(label BuildLabel) *BuildTarget {
 		state:               int32(Inactive),
 		BuildingDescription: DefaultBuildingDescription,
 		finishedBuilding:    make(chan struct{}),
+		BuildEntryPoint:     NewBuildEntrypoint(),
 	}
 }
 
diff --git a/src/output/shell_output.go b/src/output/shell_output.go
@@ -443,11 +443,16 @@ func printTempDirs(state *core.BuildState, duration time.Duration, shell, shellR
 			fmt.Printf("   Expanded: %s\n", os.Expand(cmd, env.ReplaceEnvironment))
 		} else {
 			fmt.Printf("\n")
-			argv := []string{"bash", "--noprofile", "--norc", "-o", "pipefail"}
+			buildArgvOpts := []core.BuildArgvOpt{target.BuildEntryPoint.WithBuildArgvInteractive()}
 			if shellRun {
-				argv = append(argv, "-c", cmd)
+				buildArgvOpts = append(buildArgvOpts, target.BuildEntryPoint.WithBuildArgvCommand(cmd))
 			}
-			log.Debug("Full command: %s", strings.Join(argv, " "))
+			argv, err := target.BuildEntryPoint.BuildArgv(state, target, buildArgvOpts...)
+			if err != nil {
+				log.Errorf("Could not build shell args: %s", err)
+			}
+
+			log.Debug("Full command(shellRun: %v): %#v", shellRun, argv)
 			cmd := state.ProcessExecutor.ExecCommand(process.NewSandboxConfig(shouldSandbox, shouldSandbox), false, argv[0], argv[1:]...)
 			cmd.Dir = dir
 			cmd.Env = append(cmd.Env, env.ToSlice()...)
diff --git a/src/parse/asp/targets.go b/src/parse/asp/targets.go
@@ -72,6 +72,10 @@ const (
 	fileContentArgIdx
 	subrepoArgIdx
 	noTestCoverageArgIdx
+	buildEntryPointArgIdx
+	buildEntryPointExitOnErrorArgsArgIdx
+	buildEntryPointInteractiveArgsArgIdx
+	buildEntryPointExecCommandArgsArgIdx
 )
 
 // createTarget creates a new build target as part of build_rule().
@@ -140,6 +144,8 @@ func createTarget(s *scope, args []pyObject) *core.BuildTarget {
 		target.AddLabel("remote")
 	}
 	target.Command, target.Commands = decodeCommands(s, args[cmdBuildRuleArgIdx])
+	target.BuildEntryPoint = decodeBuildEntrypointFromArgs(s, args)
+
 	if test {
 		target.Test = new(core.TestFields)
 
@@ -252,6 +258,37 @@ func decodeCommands(s *scope, obj pyObject) (string, map[string]string) {
 	return "", m
 }
 
+// decodeBuildEntrypointFromArgs takes a Python object and returns it as a BuildEntrypoint.
+func decodeBuildEntrypointFromArgs(s *scope, args []pyObject) *core.BuildEntrypoint {
+	buildEntrypointOpts := []core.BuildEntrypointOpt{}
+
+	if obj := args[buildEntryPointArgIdx]; obj != nil && obj != None {
+		buildEntrypointOpts = append(buildEntrypointOpts,
+			core.WithBuildEntrypointEntrypoint(asStringList(s, mustList(obj), "build_entry_point")),
+		)
+	}
+
+	if obj := args[buildEntryPointExecCommandArgsArgIdx]; obj != nil && obj != None {
+		buildEntrypointOpts = append(buildEntrypointOpts,
+			core.WithBuildEntrypointExecCommandArgs(asStringList(s, mustList(obj), "build_entry_point_exec_command_args")),
+		)
+	}
+
+	if obj := args[buildEntryPointExitOnErrorArgsArgIdx]; obj != nil && obj != None {
+		buildEntrypointOpts = append(buildEntrypointOpts,
+			core.WithBuildEntrypointExitOnErrorArgs(asStringList(s, mustList(obj), "build_entry_point_exit_on_error_args")),
+		)
+	}
+
+	if obj := args[buildEntryPointInteractiveArgsArgIdx]; obj != nil && obj != None {
+		buildEntrypointOpts = append(buildEntrypointOpts,
+			core.WithBuildEntrypointInteractiveArgs(asStringList(s, mustList(obj), "build_entry_point_interactive_args")),
+		)
+	}
+
+	return core.NewBuildEntrypoint(buildEntrypointOpts...)
+}
+
 // populateTarget sets the assorted attributes on a build target.
 func populateTarget(s *scope, t *core.BuildTarget, args []pyObject) {
 	if t.IsRemoteFile {
diff --git a/test/build_entrypoints/BUILD b/test/build_entrypoints/BUILD
diff --git a/test/build_entrypoints/main.go b/test/build_entrypoints/main.go
diff --git a/test/build_entrypoints/test_build_entrypoint.sh b/test/build_entrypoints/test_build_entrypoint.sh
