config: urlencode interpolation function

This escapes all characters that might have a special interpretation when embedded into a portion of a URL, including slashes, equals signs and ampersands.

config/interpolate_funcs.go

@@ -14,6 +14,7 @@ import (
 	"io/ioutil"
 	"math"
 	"net"
+	"net/url"
 	"path/filepath"
 	"regexp"
 	"sort"
@@ -111,6 +112,7 @@ func Funcs() map[string]ast.Function {
 		"title":        interpolationFuncTitle(),
 		"trimspace":    interpolationFuncTrimSpace(),
 		"upper":        interpolationFuncUpper(),
+		"urlencode":    interpolationFuncURLEncode(),
 		"zipmap":       interpolationFuncZipMap(),
 	}
 }
@@ -1517,3 +1519,14 @@ func interpolationFuncFlatten() ast.Function {
 		},
 	}
 }
+
+func interpolationFuncURLEncode() ast.Function {
+	return ast.Function{
+		ArgTypes:   []ast.Type{ast.TypeString},
+		ReturnType: ast.TypeString,
+		Callback: func(args []interface{}) (interface{}, error) {
+			s := args[0].(string)
+			return url.QueryEscape(s), nil
+		},
+	}
+}

config/interpolate_funcs_test.go

@@ -2557,3 +2557,30 @@ func TestInterpolateFuncFlatten(t *testing.T) {
 		},
 	})
 }
+
+func TestInterpolateFuncURLEncode(t *testing.T) {
+	testFunction(t, testFunctionConfig{
+		Cases: []testFunctionCase{
+			{
+				`${urlencode("abc123-_")}`,
+				"abc123-_",
+				false,
+			},
+			{
+				`${urlencode("foo:bar@localhost?foo=bar&bar=baz")}`,
+				"foo%3Abar%40localhost%3Ffoo%3Dbar%26bar%3Dbaz",
+				false,
+			},
+			{
+				`${urlencode("mailto:email?subject=this+is+my+subject")}`,
+				"mailto%3Aemail%3Fsubject%3Dthis%2Bis%2Bmy%2Bsubject",
+				false,
+			},
+			{
+				`${urlencode("foo/bar")}`,
+				"foo%2Fbar",
+				false,
+			},
+		},
+	})
+}

website/docs/configuration/interpolation.html.md

@@ -386,6 +386,8 @@ The supported built-in functions are:
 
   * `upper(string)` - Returns a copy of the string with all Unicode letters mapped to their upper case.
 
+  * `urlencode(string)` - Returns an URL-safe copy of the string.
+
   * `uuid()` - Returns a UUID string in RFC 4122 v4 format. This string will change with every invocation of the function, so in order to prevent diffs on every plan & apply, it must be used with the [`ignore_changes`](/docs/configuration/resources.html#ignore-changes) lifecycle attribute.
 
   * `values(map)` - Returns a list of the map values, in the order of the keys