Add template function for returning the path to the pack's directory

CHANGELOG.md

@@ -1,5 +1,8 @@
 ## UNRELEASED
 
+IMPROVEMENTS:
+* template: Add template function for returning the path to the pack's directory [[GH-574](https://github.com/hashicorp/nomad-pack/pull/574)]
+
 ## 0.2.0 (October 16, 2024)
 
 BREAKING CHANGES:

docs/writing-packs.md

@@ -189,7 +189,8 @@ Custom Nomad-specific and debugging functions are also provided:
 - `nomadNamespace` takes a single string parameter of a namespace ID which will be read via `/v1/namespace/:namespace`.
 - `spewDump` dumps the entirety of the passed object as a string. The output includes the content types and values. This uses the `spew.SDump` function.
 - `spewPrintf` dumps the supplied arguments into a string according to the supplied format. This utilises the `spew.Printf` function.
-- `fileContents` takes an argument to a file of the local host, reads its contents and provides this as a string.
+- `fileContents` takes an argument to a file on the local host relative to the directory `nomad-pack` is invoked in, reads its contents and provides the output as a string.
+- `packPath` returns the path to the pack being invoked.
 
 A custom function within a template is called like any other:
 

internal/pkg/manager/manager.go

@@ -118,6 +118,7 @@ func (pm *PackManager) ProcessTemplates(renderAux bool, format bool, ignoreMissi
 
 	r := new(renderer.Renderer)
 	r.Client = pm.client
+	r.PackPath = pm.cfg.Path
 	pm.renderer = r
 
 	// should auxiliary files be rendered as well?

internal/pkg/renderer/funcs.go

@@ -51,6 +51,12 @@ func funcMap(r *Renderer) template.FuncMap {
 		f["nomadRegions"] = nomadRegions(r.Client)
 	}
 
+	if r != nil && r.PackPath != "" {
+		f["packPath"] = func() (string, error) {
+			return r.PackPath, nil
+		}
+	}
+
 	// Add additional custom functions.
 	f["fileContents"] = fileContents
 	f["toStringList"] = toStringList

internal/pkg/renderer/renderer.go

@@ -27,6 +27,9 @@ type Renderer struct {
 	// set to true error will be used, otherwise zero is used.
 	Strict bool
 
+	// PackPath is the path to the pack being rendered.
+	PackPath string
+
 	// Client is the Nomad API client used when running the Nomad template
 	// functions. It can potentially be nil, therefore care should be taken
 	// when accessing it.