[ZigPlanner] Add support for shell and build (#141)

## Summary

Adds basic support for shell and build.

Build Size optimization:
- If I include the `zig` nix package in the runtimePackages, then the
image size
is really large (700MB)
- But I believe the zig executable is standalone
ziglang/zig#3660 (comment)
- So, I get the zig-executable's name by:
- parsing the `build.zig` file (so unfortunate) to find the
`addExecutable` line
- fallback: if I fail to find exactly one `addExecutable`, then I
fallback to installing the `zig` nix package and invoking `zig build
run`
- the image size is 22MB 

## How was it tested?

shell:
in the testcase folder:
```
> devbox shell

(devbox)> zig build run
# see output
info: All your codebase are belong to us.
```
Don't be alarmed! Just a printout.

build:
```
> devbox build
> docker run devbox
info: All your codebase are belong to us.
```

planner/languages/zig/zig_planner.go

@@ -4,6 +4,11 @@
 package zig
 
 import (
+	"fmt"
+	"os"
+	"regexp"
+
+	"github.com/pkg/errors"
 	"go.jetpack.io/devbox/planner/plansdk"
 )
 
@@ -17,9 +22,65 @@ func (p *Planner) Name() string {
 }
 
 func (p *Planner) IsRelevant(srcDir string) bool {
-	return false
+	a, err := plansdk.NewAnalyzer(srcDir)
+	if err != nil {
+		// We should log that an error has occurred.
+		return false
+	}
+	return a.HasAnyFile("build.zig")
 }
 
 func (p *Planner) GetPlan(srcDir string) *plansdk.Plan {
-	return &plansdk.Plan{}
+
+	var runtimePkgs []string
+	var startStage *plansdk.Stage
+	exeName, err := getZigExecutableName(srcDir)
+	if err != nil {
+		runtimePkgs = []string{"zig"}
+		startStage = &plansdk.Stage{
+			InputFiles: plansdk.AllFiles(),
+			Command:    "zig build run",
+		}
+	} else {
+		runtimePkgs = []string{}
+		startStage = &plansdk.Stage{
+			InputFiles: []string{"./zig-out/bin/"},
+			Command:    fmt.Sprintf("./%s", exeName),
+		}
+	}
+
+	return &plansdk.Plan{
+		DevPackages:     []string{"zig"},
+		RuntimePackages: runtimePkgs,
+		BuildStage: &plansdk.Stage{
+			InputFiles: plansdk.AllFiles(),
+			Command:    "zig build install",
+		},
+		StartStage: startStage,
+	}
+}
+
+func getZigExecutableName(srcDir string) (string, error) {
+	a, err := plansdk.NewAnalyzer(srcDir)
+	if err != nil {
+		// We should log that an error has occurred.
+		return "", err
+	}
+	contents, err := os.ReadFile(a.AbsPath("build.zig"))
+	if err != nil {
+		return "", errors.WithStack(err)
+	}
+
+	r := regexp.MustCompile("addExecutable\\(\"(.*)\",.+\\)")
+	matches := r.FindStringSubmatch(string(contents))
+	if len(matches) != 2 {
+		errorPrefix := "Unable to resolve executable name"
+		if len(matches) < 2 {
+			return "", errors.Errorf("%s: did not find a matching addExecutable statement", errorPrefix)
+		} else {
+			return "", errors.Errorf("%s: found more than one addExecutable statement", errorPrefix)
+		}
+	}
+	return matches[1], nil
+
 }

planner/plansdk/analyzer.go

@@ -32,7 +32,7 @@ func NewAnalyzer(rootDir string) (*Analyzer, error) {
 // AbsPath resolves the given path and turns it into an absolute path relative
 // to the root directory of the analyzer. If the given path is already absolute
 // it leaves it as is.
-func (a *Analyzer) absPath(path string) string {
+func (a *Analyzer) AbsPath(path string) string {
 	if filepath.IsAbs(path) {
 		return path
 	}
@@ -47,7 +47,7 @@ func (a *Analyzer) GlobFiles(patterns ...string) []string {
 	results := []string{}
 
 	for _, p := range patterns {
-		pattern := a.absPath(p)
+		pattern := a.AbsPath(p)
 		matches, err := doublestar.FilepathGlob(pattern)
 		if err != nil {
 			continue
@@ -58,7 +58,7 @@ func (a *Analyzer) GlobFiles(patterns ...string) []string {
 }
 
 func (a *Analyzer) FileExists(relPath string) bool {
-	_, err := os.Stat(a.absPath(relPath))
+	_, err := os.Stat(a.AbsPath(relPath))
 	return err == nil
 }
 
@@ -68,6 +68,6 @@ func (a *Analyzer) HasAnyFile(patterns ...string) bool {
 }
 
 func (a *Analyzer) ParseFile(relPath string, ptr any) error {
-	abs := a.absPath(relPath)
+	abs := a.AbsPath(relPath)
 	return cuecfg.ParseFile(abs, ptr)
 }

testdata/zig/README.md

@@ -0,0 +1,14 @@
+To create a project, I followed the instructions at:
+https://ziglang.org/learn/getting-started/#installing-zig
+
+```
+mkdir <folder>
+cd <folder>
+zig init-exe # executable gets the folder name
+
+# build the project
+zig build install
+
+# run the project
+zig build run
+```

testdata/zig/zig-hello-world/.gitignore

@@ -0,0 +1,2 @@
+zig-cache/
+zig-out/

testdata/zig/zig-hello-world/build.zig

@@ -0,0 +1,34 @@
+const std = @import("std");
+
+pub fn build(b: *std.build.Builder) void {
+    // Standard target options allows the person running `zig build` to choose
+    // what target to build for. Here we do not override the defaults, which
+    // means any target is allowed, and the default is native. Other options
+    // for restricting supported target set are available.
+    const target = b.standardTargetOptions(.{});
+
+    // Standard release options allow the person running `zig build` to select
+    // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall.
+    const mode = b.standardReleaseOptions();
+
+    const exe = b.addExecutable("zig-hello-world", "src/main.zig");
+    exe.setTarget(target);
+    exe.setBuildMode(mode);
+    exe.install();
+
+    const run_cmd = exe.run();
+    run_cmd.step.dependOn(b.getInstallStep());
+    if (b.args) |args| {
+        run_cmd.addArgs(args);
+    }
+
+    const run_step = b.step("run", "Run the app");
+    run_step.dependOn(&run_cmd.step);
+
+    const exe_tests = b.addTest("src/main.zig");
+    exe_tests.setTarget(target);
+    exe_tests.setBuildMode(mode);
+
+    const test_step = b.step("test", "Run unit tests");
+    test_step.dependOn(&exe_tests.step);
+}

testdata/zig/zig-hello-world/devbox.json

@@ -0,0 +1,6 @@
+{
+  "packages": [],
+  "shell": {
+    "init_hook": null
+  }
+}

testdata/zig/zig-hello-world/plan.json

@@ -0,0 +1,22 @@
+{
+  "dev_packages": [
+    "zig"
+  ],
+  "runtime_packages": [],
+  "install_stage": {
+    "command": ""
+  },
+  "build_stage": {
+    "command": "zig build install",
+    "input_files": [
+      "."
+    ]
+  },
+  "start_stage": {
+    "command": "./zig-hello-world",
+    "input_files": [
+      "./zig-out/bin/"
+    ]
+  },
+  "definitions": null
+}

testdata/zig/zig-hello-world/src/main.zig

@@ -0,0 +1,9 @@
+const std = @import("std");
+
+pub fn main() anyerror!void {
+    std.log.info("Hello World! You are running zig.", .{});
+}
+
+test "basic test" {
+    try std.testing.expectEqual(10, 3 + 7);
+}