feat: add nix-shell segment

src/config/segment_types.go

@@ -128,6 +128,8 @@ const (
 	NPM SegmentType = "npm"
 	// NX writes which Nx version us currently active
 	NX SegmentType = "nx"
+	// NIX writes the active nix shell details
+	NixShell SegmentType = "nix_shell"
 	// OCAML writes the active Ocaml version
 	OCAML SegmentType = "ocaml"
 	// OS write os specific icon
@@ -266,6 +268,7 @@ var Segments = map[SegmentType]func() SegmentWriter{
 	NIGHTSCOUT:      func() SegmentWriter { return &segments.Nightscout{} },
 	NODE:            func() SegmentWriter { return &segments.Node{} },
 	NPM:             func() SegmentWriter { return &segments.Npm{} },
+	NixShell:        func() SegmentWriter { return &segments.NixShell{} },
 	NX:              func() SegmentWriter { return &segments.Nx{} },
 	OCAML:           func() SegmentWriter { return &segments.OCaml{} },
 	OS:              func() SegmentWriter { return &segments.Os{} },

src/segments/nixshell.go

@@ -0,0 +1,67 @@
+package segments
+
+import (
+	"path/filepath"
+	"strings"
+
+	"github.com/jandedobbeleer/oh-my-posh/src/properties"
+	"github.com/jandedobbeleer/oh-my-posh/src/runtime"
+)
+
+type NixShellType string
+
+const (
+	PURE    NixShellType = "pure"
+	IMPURE  NixShellType = "impure"
+	UNKNOWN NixShellType = "unknown"
+	NONE    NixShellType = "none"
+)
+
+type NixShell struct {
+	props properties.Properties
+	env   runtime.Environment
+
+	ShellType string
+}
+
+func (n *NixShell) Template() string {
+	return "via {{ .ShellType }}-shell"
+}
+
+func (n *NixShell) DetectShellType() NixShellType {
+	switch n.env.Getenv("IN_NIX_SHELL") {
+	case "pure":
+		return PURE
+	case "impure":
+		return IMPURE
+	default:
+		if n.InNewNixShell() {
+			return UNKNOWN
+		}
+		return NONE
+	}
+}
+
+// Hack to detect if we're in a `nix shell` (in contrast to a `nix-shell`).
+func (n *NixShell) InNewNixShell() bool {
+	paths := filepath.SplitList(n.env.Getenv("PATH"))
+
+	for _, p := range paths {
+		if strings.Contains(p, "/nix/store") {
+			return true
+		}
+	}
+
+	return false
+}
+
+func (n *NixShell) Init(props properties.Properties, env runtime.Environment) {
+	n.props = props
+	n.env = env
+
+	n.ShellType = string(n.DetectShellType())
+}
+
+func (n *NixShell) Enabled() bool {
+	return n.ShellType != string(NONE)
+}

src/segments/nixshell_test.go

@@ -0,0 +1,76 @@
+package segments
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/alecthomas/assert"
+	"github.com/jandedobbeleer/oh-my-posh/src/properties"
+	"github.com/jandedobbeleer/oh-my-posh/src/runtime/mock"
+)
+
+const (
+	nixPath     = "/nix/store/zznw8fnzss1vaqfg5hmv3y79s3hkqczi-devshell-dir/bin"
+	defaultPath = "/users/xyz/testing"
+	fullNixPath = defaultPath + ":" + nixPath
+)
+
+func setupMockEnvironment(shellType string) *mock.Environment {
+	env := new(mock.Environment)
+	env.On("Getenv", "IN_NIX_SHELL").Return(shellType)
+	path := defaultPath
+	if shellType != "" {
+		path = fullNixPath
+	}
+	env.On("Getenv", "PATH").Return(path)
+	return env
+}
+
+func TestNixShellSegment(t *testing.T) {
+	cases := []struct {
+		name           string
+		expectedString string
+		shellType      string
+		enabled        bool
+	}{
+		{
+			name:           "Pure Nix Shell",
+			expectedString: "via pure-shell",
+			shellType:      "pure",
+			enabled:        true,
+		},
+		{
+			name:           "Impure Nix Shell",
+			expectedString: "via impure-shell",
+			shellType:      "impure",
+			enabled:        true,
+		},
+		{
+			name:           "Unknown Nix Shell",
+			expectedString: "via unknown-shell",
+			shellType:      "unknown",
+			enabled:        true,
+		},
+		{
+			name:           "No Nix Shell",
+			expectedString: "",
+			shellType:      "",
+			enabled:        false,
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			env := setupMockEnvironment(tc.shellType)
+			n := NixShell{}
+			n.Init(properties.Map{}, env)
+
+			if tc.enabled {
+				assert.True(t, n.Enabled(), fmt.Sprintf("Failed in case: %s", tc.name))
+				assert.Equal(t, tc.expectedString, renderTemplate(env, n.Template(), n), tc.name)
+			} else {
+				assert.False(t, n.Enabled())
+			}
+		})
+	}
+}

themes/schema.json

@@ -4723,6 +4723,31 @@
               }
             }
           }
+        },
+        {
+          "if": {
+            "properties": {
+              "type": {
+                "const": "nix_shell"
+              }
+            }
+          },
+          "then": {
+            "title": "Nix Shell Segment",
+            "description": "https://ohmyposh.dev/docs/segments/nix-shell",
+            "properties": {
+              "properties": {
+                "properties": {
+                  "newprop": {
+                    "type": "string",
+                    "title": "New Property",
+                    "description": "the default text to display",
+                    "default": "Hello"
+                  }
+                }
+              }
+            }
+          }
         }
       ]
     }

website/docs/segments/cli/nix-shell.mdx

@@ -0,0 +1,39 @@
+---
+id: nix-shell
+title: Nix Shell
+sidebar_label: Nix Shell
+---
+
+## What
+
+Display the [nix shell](https://nixos.org/guides/nix-pills/developing-with-nix-shell.html) status if inside a nix-shell environment.
+
+## Sample Configuration
+
+import Config from "@site/src/components/Config.js";
+
+<Config
+  data={{
+    type: "nix_shell",
+    style: "powerline",
+    foreground: "blue",
+    background: "transparent",
+    template: "(nix-{{ .ShellType }})",
+  }}
+/>
+
+## Template ([info][templates])
+
+:::note default template
+
+```template
+via {{ .ShellType }}-shell"
+```
+
+:::
+
+### Properties
+
+| Name         | Type     | Description                                                 |
+| ------------ | -------- | ----------------------------------------------------------- |
+| `.ShellType` | `string` | the type of nix shell, can be `pure`, `impure` or `unknown` |

website/sidebars.js

@@ -71,6 +71,7 @@ module.exports = {
             "segments/cli/kubectl",
             "segments/cli/mvn",
             "segments/cli/nbgv",
+            "segments/cli/nix-shell",
             "segments/cli/npm",
             "segments/cli/nx",
             "segments/cli/pnpm",