jonasz-lasut · Sep 17, 2026 · Sep 17, 2026 · Sep 17, 2026 · Sep 17, 2026 · Sep 18, 2026
@@ -53,6 +53,7 @@ const (
 	SchemaLanguageJSON   = "json"
 	SchemaLanguageKCL    = "kcl"
 	SchemaLanguagePython = "python"
+	SchemaLanguageRust   = "rust"
 )
 
 // SupportedSchemaLanguages returns the set of language identifiers accepted
@@ -63,6 +64,7 @@ func SupportedSchemaLanguages() []string {
 		SchemaLanguageJSON,
 		SchemaLanguageKCL,
 		SchemaLanguagePython,
+		SchemaLanguageRust,
 	}
 }
 
@@ -133,7 +135,7 @@ type ProjectPackageMetadata struct {
 // produced both for the project's own XRDs and for its declared dependencies.
 type ProjectSchemas struct {
 	// Languages restricts schema generation to the listed languages.
-	// Supported values are "go", "json", "kcl", and "python". If not
+	// Supported values are "go", "json", "kcl", "python", and "rust". If not
 	// specified, schemas are generated for all supported languages.
 	Languages []string `json:"languages,omitempty"`
 }

@@ -57,6 +57,9 @@ var (
 	kclTemplates embed.FS
 	//go:embed all:templates/python
 	pythonTemplates embed.FS
+	// The rust template contains a .gitignore, which embed skips without all.
+	//go:embed all:templates/rust
+	rustTemplates embed.FS
 	//go:embed templates/go-templating/*
 	goTemplatingTemplates embed.FS
 
@@ -70,7 +73,7 @@ var (
 type generateCmd struct {
 	Name         string `arg:""                    help:"Name of the function to generate. Must be a valid DNS-1035 label."`
 	PipelinePath string `arg:""                    help:"Path to a Composition YAML file to add a pipeline step to."        optional:""`
-	Language     string `default:"go-templating"   enum:"go,go-templating,kcl,python"                                       help:"Language to use for the function." short:"l"`
+	Language     string `default:"go-templating"   enum:"go,go-templating,kcl,python,rust"                                  help:"Language to use for the function." short:"l"`
 	ProjectFile  string `default:"${project_file}" help:"Path to project definition file."                                  short:"f"`
 
 	projFS            afero.Fs
@@ -180,6 +183,7 @@ func (c *generateCmd) Run(sp terminal.SpinnerPrinter, cfg *config.Config) error
 		"go-templating": c.generateGoTemplatingFiles,
 		"kcl":           c.generateKCLFiles,
 		"python":        c.generatePythonFiles,
+		"rust":          c.generateRustFiles,
 	}
 
 	generator, ok := generators[c.Language]
@@ -297,48 +301,85 @@ func (c *generateCmd) generateKCLFiles(fs afero.Fs) error {
 	return renderTemplates(fs, tmpls, tmplData)
 }
 
-type pythonTemplateData struct {
-	HasSchemas  bool
-	SchemasPath string
-}
-
-func (c *generateCmd) generatePythonFiles(targetFS afero.Fs) error {
-	hasSchemas, err := afero.DirExists(c.schemasFS, "python")
+// schemasInfo reports whether the project has generated models for a language
+// and the path at which a function of this project depends on them, relative
+// to the function's directory. A schemas directory that exists but is empty
+// counts as no models.
+func (c *generateCmd) schemasInfo(lang string) (bool, string, error) {
+	hasSchemas, err := afero.DirExists(c.schemasFS, lang)
 	if err != nil {
-		return errors.Wrap(err, "cannot inspect python schemas directory")
+		return false, "", errors.Wrapf(err, "cannot inspect %s schemas directory", lang)
 	}
 	if hasSchemas {
-		entries, err := afero.ReadDir(c.schemasFS, "python")
+		entries, err := afero.ReadDir(c.schemasFS, lang)
 		if err != nil {
-			return errors.Wrap(err, "cannot read python schemas directory")
+			return false, "", errors.Wrapf(err, "cannot read %s schemas directory", lang)
 		}
 		hasSchemas = len(entries) > 0
 	}
 
-	// Compute the relative path from the function dir to schemas/python/.
 	fnDir := filepath.Join("/", c.proj.Spec.Paths.Functions, c.Name)
 	relRoot, err := filepath.Rel(fnDir, "/")
 	if err != nil {
-		return errors.Wrap(err, "cannot determine path to schemas directory")
+		return false, "", errors.Wrap(err, "cannot determine path to schemas directory")
+	}
+
+	return hasSchemas, filepath.ToSlash(filepath.Join(relRoot, c.proj.Spec.Paths.Schemas, lang)), nil
+}
+
+// renderTemplateTree renders the templates in root into targetFS, and the
+// templates in root's sub directory into that directory of targetFS.
+// template.ParseFS does not walk subdirectories, so a scaffold laid out on two
+// levels is rendered in two passes.
+func renderTemplateTree(targetFS afero.Fs, templates fs.FS, root, sub string, data any) error {
+	tmpls := template.Must(template.ParseFS(templates, path.Join(root, "*.*")))
+	if err := renderTemplates(targetFS, tmpls, data); err != nil {
+		return err
+	}
+
+	if err := targetFS.Mkdir(sub, 0o755); err != nil {
+		return errors.Wrapf(err, "cannot create %s directory", sub)
+	}
+	tmpls = template.Must(template.ParseFS(templates, path.Join(root, sub, "*.*")))
+	return renderTemplates(afero.NewBasePathFs(targetFS, sub), tmpls, data)
+}
+
+type pythonTemplateData struct {
+	HasSchemas  bool
+	SchemasPath string
+}
+
+func (c *generateCmd) generatePythonFiles(targetFS afero.Fs) error {
+	hasSchemas, schemasPath, err := c.schemasInfo("python")
+	if err != nil {
+		return err
 	}
-	schemasPath := filepath.ToSlash(filepath.Join(relRoot, c.proj.Spec.Paths.Schemas, "python"))
 
-	// template.ParseFS doesn't handle subdirectories, so we need to template
-	// the top-level directory and the 'function' sub-directory separately.
 	data := pythonTemplateData{
 		HasSchemas:  hasSchemas,
 		SchemasPath: schemasPath,
 	}
-	tmpls := template.Must(template.ParseFS(pythonTemplates, "templates/python/*.*"))
-	if err := renderTemplates(targetFS, tmpls, data); err != nil {
+	return renderTemplateTree(targetFS, pythonTemplates, "templates/python", "function", data)
+}
+
+type rustTemplateData struct {
+	Name        string
+	HasSchemas  bool
+	SchemasPath string
+}
+
+func (c *generateCmd) generateRustFiles(targetFS afero.Fs) error {
+	hasSchemas, schemasPath, err := c.schemasInfo("rust")
+	if err != nil {
 		return err
 	}
 
-	if err := targetFS.Mkdir("function", 0o755); err != nil {
-		return errors.Wrap(err, "cannot create function directory")
+	data := rustTemplateData{
+		Name:        c.Name,
+		HasSchemas:  hasSchemas,
+		SchemasPath: schemasPath,
 	}
-	tmpls = template.Must(template.ParseFS(pythonTemplates, "templates/python/function/*.*"))
-	return renderTemplates(afero.NewBasePathFs(targetFS, "function"), tmpls, data)
+	return renderTemplateTree(targetFS, rustTemplates, "templates/rust", "src", data)
 }
 
 type goTemplateData struct {

@@ -186,6 +186,104 @@ func TestGenerateKCLFiles(t *testing.T) {
 	}
 }
 
+func TestSchemasInfo(t *testing.T) {
+	cases := map[string]struct {
+		reason string
+		args   struct {
+			lang           string
+			seedSchemas    map[string][]byte
+			seedSchemaDirs []string
+			paths          v1alpha1.ProjectPaths
+		}
+		want struct {
+			hasSchemas  bool
+			schemasPath string
+		}
+	}{
+		"NoSchemasDirectory": {
+			reason: "A project without models for the language has no schemas, but the path is computed all the same.",
+			args: struct {
+				lang           string
+				seedSchemas    map[string][]byte
+				seedSchemaDirs []string
+				paths          v1alpha1.ProjectPaths
+			}{lang: "rust", paths: v1alpha1.ProjectPaths{Functions: "functions", Schemas: "schemas"}},
+			want: struct {
+				hasSchemas  bool
+				schemasPath string
+			}{hasSchemas: false, schemasPath: "../../schemas/rust"},
+		},
+		"EmptySchemasDirectory": {
+			reason: "A schemas directory with nothing in it counts as no models.",
+			args: struct {
+				lang           string
+				seedSchemas    map[string][]byte
+				seedSchemaDirs []string
+				paths          v1alpha1.ProjectPaths
+			}{lang: "python", seedSchemaDirs: []string{"python"}, paths: v1alpha1.ProjectPaths{Functions: "functions", Schemas: "schemas"}},
+			want: struct {
+				hasSchemas  bool
+				schemasPath string
+			}{hasSchemas: false, schemasPath: "../../schemas/python"},
+		},
+		"GeneratedModels": {
+			reason: "A populated schemas directory means the function can depend on the models.",
+			args: struct {
+				lang           string
+				seedSchemas    map[string][]byte
+				seedSchemaDirs []string
+				paths          v1alpha1.ProjectPaths
+			}{lang: "rust", seedSchemas: map[string][]byte{"rust/Cargo.toml": nil}, paths: v1alpha1.ProjectPaths{Functions: "functions", Schemas: "schemas"}},
+			want: struct {
+				hasSchemas  bool
+				schemasPath string
+			}{hasSchemas: true, schemasPath: "../../schemas/rust"},
+		},
+		"ProjectPaths": {
+			reason: "The path follows the project's own functions and schemas directories.",
+			args: struct {
+				lang           string
+				seedSchemas    map[string][]byte
+				seedSchemaDirs []string
+				paths          v1alpha1.ProjectPaths
+			}{lang: "python", seedSchemas: map[string][]byte{"python/models/__init__.py": nil}, paths: v1alpha1.ProjectPaths{Functions: "src/functions", Schemas: "generated/models"}},
+			want: struct {
+				hasSchemas  bool
+				schemasPath string
+			}{hasSchemas: true, schemasPath: "../../../generated/models/python"},
+		},
+	}
+
+	for name, tc := range cases {
+		t.Run(name, func(t *testing.T) {
+			schemasFS := seedFS(t, tc.args.seedSchemas)
+			for _, dir := range tc.args.seedSchemaDirs {
+				if err := schemasFS.MkdirAll(dir, 0o755); err != nil {
+					t.Fatal(err)
+				}
+			}
+			paths := tc.args.paths
+			c := &generateCmd{
+				Name:      "my-func",
+				schemasFS: schemasFS,
+				proj:      &v1alpha1.Project{Spec: v1alpha1.ProjectSpec{Paths: &paths}},
+			}
+
+			hasSchemas, schemasPath, err := c.schemasInfo(tc.args.lang)
+			if err != nil {
+				t.Fatalf("\n%s\nschemasInfo(%q): %v", tc.reason, tc.args.lang, err)
+			}
+			got := struct {
+				hasSchemas  bool
+				schemasPath string
+			}{hasSchemas: hasSchemas, schemasPath: schemasPath}
+			if diff := cmp.Diff(tc.want, got, cmp.AllowUnexported(got)); diff != "" {
+				t.Errorf("\n%s\nschemasInfo(%q): -want, +got:\n%s", tc.reason, tc.args.lang, diff)
+			}
+		})
+	}
+}
+
 func TestGeneratePythonFiles(t *testing.T) {
 	cases := map[string]struct {
 		seedSchemas     map[string][]byte
@@ -233,6 +331,75 @@ func TestGeneratePythonFiles(t *testing.T) {
 	}
 }
 
+func TestGenerateRustFiles(t *testing.T) {
+	cases := map[string]struct {
+		seedSchemas     map[string][]byte
+		seedSchemaDirs  []string
+		wantFiles       []string
+		wantContains    map[string][]byte
+		wantNotContains map[string][]byte
+	}{
+		"NoSchemas": {
+			wantFiles: []string{
+				".gitignore",
+				"Cargo.toml",
+				"README.md",
+				"rust-toolchain.toml",
+				"src/main.rs",
+				"src/function.rs",
+			},
+			wantContains: map[string][]byte{
+				"Cargo.toml": []byte(`name = "my-func"`),
+				"README.md":  []byte("# my-func"),
+			},
+			wantNotContains: map[string][]byte{
+				"Cargo.toml":      []byte("crossplane-models"),
+				"README.md":       []byte("crossplane-models"),
+				"src/function.rs": []byte("crossplane_models"),
+			},
+		},
+		"WithSchemas": {
+			seedSchemas: map[string][]byte{
+				"rust/Cargo.toml": nil,
+			},
+			wantContains: map[string][]byte{
+				"Cargo.toml":      []byte(`crossplane-models = { path = "../../schemas/rust" }`),
+				"README.md":       []byte("`../../schemas/rust`"),
+				"src/function.rs": []byte("use crossplane_models::"),
+			},
+		},
+		"EmptySchemasDirectory": {
+			seedSchemaDirs: []string{"rust"},
+			wantNotContains: map[string][]byte{
+				"Cargo.toml": []byte("crossplane-models"),
+			},
+		},
+	}
+
+	for name, tc := range cases {
+		t.Run(name, func(t *testing.T) {
+			schemasFS := seedFS(t, tc.seedSchemas)
+			for _, dir := range tc.seedSchemaDirs {
+				if err := schemasFS.MkdirAll(dir, 0o755); err != nil {
+					t.Fatal(err)
+				}
+			}
+
+			c := &generateCmd{
+				Name:      "my-func",
+				schemasFS: schemasFS,
+				proj:      testProject(),
+			}
+			fs := afero.NewMemMapFs()
+			if err := c.generateRustFiles(fs); err != nil {
+				t.Fatal(err)
+			}
+			assertFiles(t, fs, tc.wantFiles)
+			assertContains(t, fs, tc.wantContains, tc.wantNotContains)
+		})
+	}
+}
+
 func TestGenerateGoFiles(t *testing.T) {
 	cases := map[string]struct {
 		seedSchemas  map[string][]byte

@@ -11,6 +11,7 @@ The following are valid arguments to the `--language` / `-l` flag:
 - `go`
 - `kcl`
 - `python`
+- `rust`
 
 ## Examples
 
@@ -27,6 +28,12 @@ Create a Python function in `functions/fn2`:
 crossplane function generate fn2 --language python
 ```
 
+Create a Rust function in `functions/fn3`:
+
+```shell
+crossplane function generate fn3 --language rust
+```
+
 Create a Go function in `functions/compose-cluster` and add it as a pipeline
 step in the given Composition:
 

@@ -0,0 +1 @@
+target/