Merge pull request #31220 from FooBartn/string-starts-ends-with-funcs

feat: add startswith and endswith funcs

Author: alisdair

internal/lang/funcs/string.go

@@ -8,6 +8,58 @@ import (
 	"github.com/zclconf/go-cty/cty/function"
 )
 
+// StartsWithFunc constructs a function that checks if a string starts with
+// a specific prefix using strings.HasPrefix
+var StartsWithFunc = function.New(&function.Spec{
+	Params: []function.Parameter{
+		{
+			Name: "str",
+			Type: cty.String,
+		},
+		{
+			Name: "prefix",
+			Type: cty.String,
+		},
+	},
+	Type: function.StaticReturnType(cty.Bool),
+	Impl: func(args []cty.Value, retType cty.Type) (cty.Value, error) {
+		str := args[0].AsString()
+		prefix := args[1].AsString()
+
+		if strings.HasPrefix(str, prefix) {
+			return cty.True, nil
+		}
+
+		return cty.False, nil
+	},
+})
+
+// EndsWithFunc constructs a function that checks if a string ends with
+// a specific suffix using strings.HasSuffix
+var EndsWithFunc = function.New(&function.Spec{
+	Params: []function.Parameter{
+		{
+			Name: "str",
+			Type: cty.String,
+		},
+		{
+			Name: "suffix",
+			Type: cty.String,
+		},
+	},
+	Type: function.StaticReturnType(cty.Bool),
+	Impl: func(args []cty.Value, retType cty.Type) (cty.Value, error) {
+		str := args[0].AsString()
+		suffix := args[1].AsString()
+
+		if strings.HasSuffix(str, suffix) {
+			return cty.True, nil
+		}
+
+		return cty.False, nil
+	},
+})
+
 // ReplaceFunc constructs a function that searches a given string for another
 // given substring, and replaces each occurence with a given replacement string.
 var ReplaceFunc = function.New(&function.Spec{

internal/lang/functions.go

@@ -59,6 +59,7 @@ func (s *Scope) Functions() map[string]function.Function {
 			"dirname":          funcs.DirnameFunc,
 			"distinct":         stdlib.DistinctFunc,
 			"element":          stdlib.ElementFunc,
+			"endswith":         funcs.EndsWithFunc,
 			"chunklist":        stdlib.ChunklistFunc,
 			"file":             funcs.MakeFileFunc(s.BaseDir, false),
 			"fileexists":       funcs.MakeFileExistsFunc(s.BaseDir),
@@ -115,6 +116,7 @@ func (s *Scope) Functions() map[string]function.Function {
 			"slice":            stdlib.SliceFunc,
 			"sort":             stdlib.SortFunc,
 			"split":            stdlib.SplitFunc,
+			"startswith":       funcs.StartsWithFunc,
 			"strrev":           stdlib.ReverseFunc,
 			"substr":           stdlib.SubstrFunc,
 			"sum":              funcs.SumFunc,

internal/lang/functions_test.go

@@ -314,6 +314,47 @@ func TestFunctions(t *testing.T) {
 			},
 		},
 
+		"endswith": {
+			{
+				`endswith("hello world", "world")`,
+				cty.True,
+			},
+			{
+				`endswith("hello world", "hello")`,
+				cty.False,
+			},
+			{
+				`endswith("hello world", "")`,
+				cty.True,
+				// Completely empty suffix value  ( "" )
+				// will always evaluate to true for all strings.
+			},
+			{
+				`endswith("hello world", " ")`,
+				cty.False,
+			},
+			{
+				`endswith("", "")`,
+				cty.True,
+			},
+			{
+				`endswith("", " ")`,
+				cty.False,
+			},
+			{
+				`endswith(" ", "")`,
+				cty.True,
+			},
+			{
+				`endswith("", "hello")`,
+				cty.False,
+			},
+			{
+				`endswith(" ", "hello")`,
+				cty.False,
+			},
+		},
+
 		"file": {
 			{
 				`file("hello.txt")`,
@@ -816,6 +857,47 @@ func TestFunctions(t *testing.T) {
 			},
 		},
 
+		"startswith": {
+			{
+				`startswith("hello world", "hello")`,
+				cty.True,
+			},
+			{
+				`startswith("hello world", "world")`,
+				cty.False,
+			},
+			{
+				`startswith("hello world", "")`,
+				cty.True,
+				// Completely empty prefix value  ( "" )
+				// will always evaluate to true for all strings.
+			},
+			{
+				`startswith("hello world", " ")`,
+				cty.False,
+			},
+			{
+				`startswith("", "")`,
+				cty.True,
+			},
+			{
+				`startswith("", " ")`,
+				cty.False,
+			},
+			{
+				`startswith(" ", "")`,
+				cty.True,
+			},
+			{
+				`startswith("", "hello")`,
+				cty.False,
+			},
+			{
+				`startswith(" ", "hello")`,
+				cty.False,
+			},
+		},
+
 		"strrev": {
 			{
 				`strrev("hello world")`,

website/data/language-nav-data.json

@@ -319,6 +319,10 @@
             "title": "<code>chomp</code>",
             "href": "/language/functions/chomp"
           },
+          {
+            "title": "<code>endswith</code>",
+            "href": "/language/functions/endswith"
+          },
           {
             "title": "<code>format</code>",
             "href": "/language/functions/format"
@@ -352,6 +356,10 @@
             "title": "<code>split</code>",
             "href": "/language/functions/split"
           },
+          {
+            "title": "<code>startswith</code>",
+            "href": "/language/functions/startswith"
+          },
           {
             "title": "<code>strrev</code>",
             "href": "/language/functions/strrev"
@@ -776,6 +784,7 @@
       { "title": "dirname", "path": "functions/dirname", "hidden": true },
       { "title": "distinct", "path": "functions/distinct", "hidden": true },
       { "title": "element", "path": "functions/element", "hidden": true },
+      { "title": "endswith", "path": "functions/endswith", "hidden": true },
       { "title": "file", "path": "functions/file", "hidden": true },
       { "title": "filebase64", "path": "functions/filebase64", "hidden": true },
       {
@@ -851,6 +860,7 @@
       { "title": "slice", "path": "functions/slice", "hidden": true },
       { "title": "sort", "path": "functions/sort", "hidden": true },
       { "title": "split", "path": "functions/split", "hidden": true },
+      { "title": "startswith", "path": "functions/startswith", "hidden": true },
       { "title": "strrev", "path": "functions/strrev", "hidden": true },
       { "title": "substr", "path": "functions/substr", "hidden": true },
       { "title": "sum", "path": "functions/sum", "hidden": true },

website/docs/language/functions/endswith.mdx

@@ -0,0 +1,27 @@
+---
+page_title: endswith - Functions - Configuration Language
+description: |-
+  The endswith function takes two values: a string to check and a suffix string. It returns true if the first string ends with that exact suffix.
+---
+
+# `endswith` Function
+
+`endswith` takes two values: a string to check and a suffix string. The function returns true if the first string ends with that exact suffix.
+
+```hcl
+endswith(string, suffix)
+```
+
+## Examples
+
+```
+> endswith("hello world", "world")
+true
+
+> endswith("hello world", "hello")
+false
+```
+
+## Related Functions
+
+- [`startswith`](/language/functions/startswith) takes two values: a string to check and a prefix string. The function returns true if the string begins with that exact prefix.

website/docs/language/functions/startswith.mdx

@@ -0,0 +1,27 @@
+---
+page_title: startsswith - Functions - Configuration Language
+description: |-
+  The startswith function  takes two values: a string to check and a prefix string. It returns true if the string begins with that exact prefix.
+---
+
+# `startswith` Function
+
+`startswith` takes two values: a string to check and a prefix string. The function returns true if the string begins with that exact prefix.
+
+```hcl
+startswith(string, prefix)
+```
+
+## Examples
+
+```
+> startswith("hello world", "hello")
+true
+
+> startswith("hello world", "world")
+false
+```
+
+## Related Functions
+
+- [`endswith`](/language/functions/endswith) takes two values: a string to check and a suffix string. The function returns true if the first string ends with that exact suffix.

website/layouts/language.erb

@@ -370,6 +370,10 @@
                 <a href="/docs/language/functions/chomp.html">chomp</a>
               </li>
 
+              <li>
+                <a href="/docs/language/functions/endswith.html">endswith</a>
+              </li>
+
               <li>
                 <a href="/docs/language/functions/format.html">format</a>
               </li>
@@ -406,6 +410,10 @@
                 <a href="/docs/language/functions/split.html">split</a>
               </li>
 
+              <li>
+                <a href="/docs/language/functions/startswith.html">startswith</a>
+              </li>
+
               <li>
                 <a href="/docs/language/functions/strrev.html">strrev</a>
               </li>