New plugin args option

Dockerfile

@@ -38,7 +38,7 @@ COPY --from=build /bin/gomplate_${TARGETOS}-${TARGETARCH}${TARGETVARIANT} /gompl
 
 ENTRYPOINT [ "/gomplate" ]
 
-FROM alpine:3.17 AS gomplate-alpine
+FROM alpine:3.17.3 AS gomplate-alpine
 
 ARG VCS_REF
 ARG TARGETOS

docs/content/config.md

@@ -304,15 +304,19 @@ See [`--plugin`](../usage/#plugin).
 A map that configures custom functions for use in the templates. The key is the
 name of the function, and the value configures the plugin. The value is a map
 containing the command (`cmd`) and the options `pipe` (boolean) and `timeout`
-(duration).
+(duration). A list of optional arguments to always pass to the plugin can be set
+with `args` (array of strings).
 
-Alternatively, the value can be a string, which sets `cmd`.
+Alternatively, the value can be a string, which sets only `cmd`.
 
 ```yaml
-in: '{{ "hello world" | figlet | lolcat }}'
+in: '{{ "world" | figlet | lolcat }}'
 plugins:
   figlet:
     cmd: /usr/local/bin/figlet
+    args:
+      - oh
+      - hello
     pipe: true
     timeout: 1s
   lolcat: /home/hairyhenderson/go/bin/lolcat
@@ -322,6 +326,33 @@ plugins:
 
 The path to the plugin executable (or script) to run.
 
+### `args`
+
+An array of optional arguments to always pass to the plugin. These arguments
+will be passed _before_ any arguments provided in the template.
+
+For example:
+
+```yaml
+plugins:
+  echo:
+    cmd: /bin/echo
+    args:
+      - foo
+      - bar
+```
+
+With this template:
+```
+{{ echo "baz" }}
+```
+
+Will result the command being called like this:
+
+```console
+$ /bin/echo foo bar baz
+```
+
 ### `pipe`
 
 Whether to pipe the final argument of the template function to the plugin's

internal/config/configfile.go

@@ -153,8 +153,9 @@ func (d DataSource) mergeFrom(o DataSource) DataSource {
 
 type PluginConfig struct {
 	Cmd     string
-	Timeout time.Duration
-	Pipe    bool
+	Args    []string      `yaml:"args,omitempty"`
+	Timeout time.Duration `yaml:"timeout,omitempty"`
+	Pipe    bool          `yaml:"pipe,omitempty"`
 }
 
 // UnmarshalYAML - satisfy the yaml.Umarshaler interface - plugin configs can
@@ -178,6 +179,7 @@ func (p *PluginConfig) UnmarshalYAML(value *yaml.Node) error {
 
 	type raw struct {
 		Cmd     string
+		Args    []string
 		Timeout time.Duration
 		Pipe    bool
 	}

internal/config/configfile_test.go

@@ -626,16 +626,17 @@ pluginTimeout: 500ms
 	c = &Config{
 		Plugins: map[string]PluginConfig{
 			"foo": {
-				Cmd:  "bar",
-				Pipe: true,
+				Cmd:     "bar",
+				Timeout: 1 * time.Second,
+				Pipe:    true,
 			},
 		},
 	}
 	expected = `---
 plugins:
   foo:
     cmd: bar
-    timeout: 0s
+    timeout: 1s
     pipe: true
 `
 

internal/tests/integration/plugins_test.go

@@ -111,3 +111,17 @@ plugins:
 	assert.Equal(t, "", e)
 	assert.Equal(t, "=hi=thZrZ", o)
 }
+
+func TestPlugins_Args(t *testing.T) {
+	tmpDir := setupPluginsTest(t)
+
+	writeConfig(t, tmpDir, `in: '{{ echo "world" }}'
+plugins:
+  echo:
+    cmd: echo
+    args: [ oh, hello ]
+`)
+
+	o, e, err := cmd(t).withDir(tmpDir.Path()).run()
+	assertSuccess(t, o, e, err, "oh hello world\n")
+}

plugins.go

@@ -37,6 +37,7 @@ func bindPlugins(ctx context.Context, cfg *config.Config, funcMap template.FuncM
 			Timeout: timeout,
 			Pipe:    v.Pipe,
 			Stderr:  cfg.Stderr,
+			Args:    v.Args,
 		})
 	}
 
@@ -49,6 +50,10 @@ type PluginOpts struct {
 	// Defaults to os.Stderr.
 	Stderr io.Writer
 
+	// Args are additional arguments to pass to the plugin. These precede any
+	// arguments passed to the plugin function at runtime.
+	Args []string
+
 	// Timeout is the maximum amount of time to wait for the plugin to complete.
 	// Defaults to 5 seconds.
 	Timeout time.Duration
@@ -74,6 +79,7 @@ func PluginFunc(ctx context.Context, cmd string, opts PluginOpts) func(...interf
 	plugin := &plugin{
 		ctx:     ctx,
 		path:    cmd,
+		args:    opts.Args,
 		timeout: timeout,
 		pipe:    opts.Pipe,
 		stderr:  stderr,
@@ -87,6 +93,7 @@ type plugin struct {
 	ctx     context.Context
 	stderr  io.Writer
 	path    string
+	args    []string
 	timeout time.Duration
 	pipe    bool
 }
@@ -122,6 +129,7 @@ func findPowershell() string {
 
 func (p *plugin) run(args ...interface{}) (interface{}, error) {
 	a := conv.ToStrings(args...)
+	a = append(p.args, a...)
 
 	name, a := p.buildCommand(a)
 

plugins_test.go

@@ -73,6 +73,30 @@ func TestRun(t *testing.T) {
 	require.NoError(t, err)
 	assert.Equal(t, "", stderr.String())
 	assert.Equal(t, "foo", strings.TrimSpace(out.(string)))
+
+	p = &plugin{
+		ctx:     ctx,
+		timeout: 500 * time.Millisecond,
+		stderr:  stderr,
+		path:    "echo",
+		args:    []string{"foo", "bar"},
+	}
+	out, err = p.run()
+	require.NoError(t, err)
+	assert.Equal(t, "", stderr.String())
+	assert.Equal(t, "foo bar", strings.TrimSpace(out.(string)))
+
+	p = &plugin{
+		ctx:     ctx,
+		timeout: 500 * time.Millisecond,
+		stderr:  stderr,
+		path:    "echo",
+		args:    []string{"foo", "bar"},
+	}
+	out, err = p.run("baz", "qux")
+	require.NoError(t, err)
+	assert.Equal(t, "", stderr.String())
+	assert.Equal(t, "foo bar baz qux", strings.TrimSpace(out.(string)))
 }
 
 func ExamplePluginFunc() {