test: update examples to use latest chomp combinators and test through nix (#91)

Closes #90

Signed-off-by: purpleclay <purpleclaygh@gmail.com>

Author: purpleclay

.github/workflows/nix.yml

@@ -0,0 +1,59 @@
+name: nix
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - "**.go"
+      - "**.nix"
+      - "flake.lock"
+      - "examples/**"
+  pull_request:
+    branches:
+      - main
+    paths:
+      - "**.go"
+      - "**.nix"
+      - "flake.lock"
+      - "examples/**"
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+  examples:
+    runs-on: ${{ matrix.os }}
+    name: examples (${{ matrix.os }})
+    strategy:
+      matrix:
+        os: [ubuntu-24.04, macos-latest]
+    steps:
+      - name: Checkout
+        uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
+
+      - name: Install Nix
+        uses: cachix/install-nix-action@4e002c8ec80594ecd40e759629461e26c8abed15 # v31
+        with:
+          github_access_token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Setup Cachix
+        uses: cachix/cachix-action@3ba601ff5bbb07c7220846facfa2cd81eeee15a1 # v16
+        with:
+          name: purpleclay
+          authToken: "${{ secrets.GH_CACHIX }}"
+          skipPush: true
+          useDaemon: false
+
+      - name: Build and run git-diff example
+        run: |
+          nix build .#git-diff
+          ./result/bin/git-diff
+
+      - name: Build and run gpg example
+        run: |
+          nix build .#gpg
+          ./result/bin/gpg

.gitignore

@@ -19,11 +19,13 @@
 !.envrc
 !flake.nix
 !flake.lock
+!*.nix
 
 # Allow Go files
 !*.go
 !go.sum
 !go.mod
+!govendor.toml
 
 # Recurse through sub-directories applying the same patterns
 !*/

default.nix

@@ -0,0 +1,33 @@
+{
+  lib,
+  buildGoApplication,
+  go-bin,
+}: let
+  examples = [
+    "git-diff"
+    "gpg"
+  ];
+
+  mkExample = name:
+    buildGoApplication {
+      pname = "chomp-example-${name}";
+      version = "0.1.0";
+      src = ./examples;
+      go = go-bin.fromGoMod ./examples/go.mod;
+      modules = ./examples/govendor.toml;
+      subPackages = [name];
+
+      # Provide the chomp library source for the local replace directive
+      # (go.mod has: replace github.com/purpleclay/chomp => ../)
+      localReplaces = {
+        "github.com/purpleclay/chomp" = ./.;
+      };
+
+      meta = with lib; {
+        description = "Chomp parser combinator example: ${name}";
+        homepage = "https://github.com/purpleclay/chomp";
+        license = licenses.mit;
+      };
+    };
+in
+  lib.genAttrs examples mkExample

examples/git-diff/main.go

@@ -95,21 +95,27 @@ func Parse(in string) (FileDiff, error) {
 	}, nil
 }
 
+// diffPath parses the diff header line and extracts the file path.
+// Uses Recognize to capture the raw path text from "a/path" format.
 func diffPath() chomp.Combinator[string] {
 	return func(s string) (string, string, error) {
 		// diff --git a/scan/scanner.go b/scan/scanner.go
-		var rem string
-		var err error
-
-		if rem, _, err = chomp.Tag("diff --git ")(s); err != nil {
-			return rem, "", err
+		rem, _, err := chomp.Tag("diff --git ")(s)
+		if err != nil {
+			return s, "", err
 		}
 
-		var path string
-		if rem, path, err = chomp.Until(" ")(rem); err != nil {
+		// Use Recognize to capture "a/path" as raw text, then extract path after "/"
+		var rawPath string
+		rem, rawPath, err = chomp.Recognize(
+			chomp.Pair(chomp.Tag("a/"), chomp.Until(" ")),
+		)(rem)
+		if err != nil {
 			return rem, "", err
 		}
-		path = path[strings.Index(path, "/")+1:]
+
+		// Strip the "a/" prefix
+		path := rawPath[2:]
 
 		rem, _, err = chomp.Eol()(rem)
 		return rem, path, err
@@ -166,11 +172,7 @@ func diffChunk() chomp.Combinator[[]string] {
 			+       "bytes"
 			+)
 		*/
-		var rem string
-		var err error
-
-		var changes []string
-		rem, changes, err = chomp.Delimited(
+		rem, changes, err := chomp.Delimited(
 			chomp.Tag(hdrDelim+" "),
 			chomp.SepPair(diffChunkHeaderChange(remPrefix), chomp.Tag(" "), diffChunkHeaderChange(addPrefix)),
 			chomp.Eol(),
@@ -201,16 +203,24 @@ func diffChunk() chomp.Combinator[[]string] {
 	}
 }
 
+// diffChunkHeaderChange parses line number and optional count from chunk header.
+// Uses Verify to ensure line numbers are valid positive integers.
 func diffChunkHeaderChange(prefix string) chomp.Combinator[[]string] {
 	return func(s string) (string, []string, error) {
+		// Matches patterns like "-25" or "+3,3"
 		rem, _, err := chomp.Tag(prefix)(s)
 		if err != nil {
 			return rem, nil, err
 		}
 
 		return chomp.All(
-			chomp.While(chomp.IsDigit),
-			chomp.Opt(chomp.Prefixed(chomp.While(chomp.IsDigit), chomp.Tag(","))),
+			// Line number - verify it's a valid positive integer
+			chomp.Verify(chomp.Digit(), func(s string) bool {
+				n, err := strconv.Atoi(s)
+				return err == nil && n >= 0
+			}),
+			// Optional count (,N) - defaults to empty string if not present
+			chomp.Opt(chomp.Prefixed(chomp.Digit(), chomp.Tag(","))),
 		)(rem)
 	}
 }

examples/govendor.toml

@@ -0,0 +1,58 @@
+# Generated by govendor. DO NOT EDIT.
+
+schema = 2
+hash = "sha256-yYymUduCjOVIgSynlI/pyuLsq8JO57L4CYiuq/do7nk="
+
+[mod]
+  [mod."github.com/aymanbagabas/go-osc52/v2"]
+    version = "v2.0.1"
+    hash = "sha256-6Bp0jBZ6npvsYcKZGHHIUSVSTAMEyieweAX2YAKDjjg="
+    go = "1.16"
+    packages = ["github.com/aymanbagabas/go-osc52/v2"]
+  [mod."github.com/charmbracelet/lipgloss"]
+    version = "v0.12.1"
+    hash = "sha256-Uqv5hbHAxe7u94iBbAhR/de4VwWbIAw+t89We4ufiss="
+    go = "1.18"
+    packages = ["github.com/charmbracelet/lipgloss"]
+  [mod."github.com/charmbracelet/x/ansi"]
+    version = "v0.1.4"
+    hash = "sha256-hfyC3QY43qeXJGngTKdCDMoawfIJHeAC3BW4Wj461KQ="
+    go = "1.18"
+    packages = ["github.com/charmbracelet/x/ansi", "github.com/charmbracelet/x/ansi/parser"]
+  [mod."github.com/lucasb-eyer/go-colorful"]
+    version = "v1.2.0"
+    hash = "sha256-Gg9dDJFCTaHrKHRR1SrJgZ8fWieJkybljybkI9x0gyE="
+    go = "1.12"
+    packages = ["github.com/lucasb-eyer/go-colorful"]
+  [mod."github.com/mattn/go-isatty"]
+    version = "v0.0.20"
+    hash = "sha256-qhw9hWtU5wnyFyuMbKx+7RB8ckQaFQ8D+8GKPkN3HHQ="
+    go = "1.15"
+    packages = ["github.com/mattn/go-isatty"]
+  [mod."github.com/mattn/go-runewidth"]
+    version = "v0.0.15"
+    hash = "sha256-WP39EU2UrQbByYfnwrkBDoKN7xzXsBssDq3pNryBGm0="
+    go = "1.9"
+    packages = ["github.com/mattn/go-runewidth"]
+  [mod."github.com/muesli/termenv"]
+    version = "v0.15.2"
+    hash = "sha256-Eum/SpyytcNIchANPkG4bYGBgcezLgej7j/+6IhqoMU="
+    go = "1.17"
+    packages = ["github.com/muesli/termenv"]
+  [mod."github.com/purpleclay/chomp"]
+    version = "v0.0.0-20240108065605-b5889a9b1ff2"
+    hash = "sha256-F5lIAlrnoWNlRq6mNMmgEK+zXTtQLFZhDTyoWF7nSHc="
+    go = "1.22.12"
+    packages = ["github.com/purpleclay/chomp"]
+    replaced = "github.com/purpleclay/chomp"
+    local = "../"
+  [mod."github.com/rivo/uniseg"]
+    version = "v0.4.7"
+    hash = "sha256-rDcdNYH6ZD8KouyyiZCUEy8JrjOQoAkxHBhugrfHjFo="
+    go = "1.18"
+    packages = ["github.com/rivo/uniseg"]
+  [mod."golang.org/x/sys"]
+    version = "v0.19.0"
+    hash = "sha256-cmuL31TYLJmDm/fDnI2Sn0wB88cpdOHV1+urorsJWx4="
+    go = "1.18"
+    packages = ["golang.org/x/sys/unix", "golang.org/x/sys/windows"]

examples/gpg/main.go

@@ -133,18 +133,13 @@ func key() chomp.Combinator[[]string] {
 	}
 }
 
+// colon parses a colon-delimited field, using Suffixed to consume the trailing colon.
 func colon() chomp.Combinator[string] {
-	return func(s string) (string, string, error) {
-		// <any>:
-		rem, ext, err := chomp.Pair(chomp.Until(":"), chomp.Tag(":"))(s)
-		if err != nil {
-			return rem, "", err
-		}
-
-		return rem, ext[0], nil
-	}
+	return chomp.Suffixed(chomp.Until(":"), chomp.Tag(":"))
 }
 
+// fingerprint parses the fingerprint line (fpr) and validates it is 40 hex characters.
+// Uses Verify to ensure the fingerprint has the correct format.
 func fingerprint() chomp.Combinator[string] {
 	return func(s string) (string, string, error) {
 		// fpr:::::::::28BF65E18407FD2966565284AAC7E54CBD73F690:
@@ -155,8 +150,12 @@ func fingerprint() chomp.Combinator[string] {
 			return rem, "", err
 		}
 
+		// Use Verify to ensure fingerprint is exactly 40 hex characters
 		var fpr string
-		if rem, fpr, err = chomp.Until(":")(rem); err != nil {
+		if rem, fpr, err = chomp.Verify(
+			chomp.HexDigit(),
+			func(s string) bool { return len(s) == 40 },
+		)(rem); err != nil {
 			return rem, "", err
 		}
 
@@ -167,6 +166,8 @@ func fingerprint() chomp.Combinator[string] {
 	}
 }
 
+// keygrip parses the keygrip line (grp) and validates it is 40 hex characters.
+// Uses Verify to ensure the keygrip has the correct format.
 func keygrip() chomp.Combinator[string] {
 	return func(s string) (string, string, error) {
 		// grp:::::::::12E86CE47CEB942D2A65B4D02106657BA8D0C92B:
@@ -177,8 +178,12 @@ func keygrip() chomp.Combinator[string] {
 			return rem, "", err
 		}
 
+		// Use Verify to ensure keygrip is exactly 40 hex characters
 		var grp string
-		if rem, grp, err = chomp.Until(":")(rem); err != nil {
+		if rem, grp, err = chomp.Verify(
+			chomp.HexDigit(),
+			func(s string) bool { return len(s) == 40 },
+		)(rem); err != nil {
 			return rem, "", err
 		}
 

flake.lock

@@ -51,8 +51,15 @@
             };
           };
         };
+        examples = pkgs.callPackage ./default.nix {};
       in
         with pkgs; {
+          packages =
+            examples
+            // {
+              default = examples.git-diff;
+            };
+
           devShells.default = mkShell {
             inherit (pre-commit-check) shellHook;
 
@@ -62,6 +69,7 @@
                 (go-bin.fromGoMod "${self}/go.mod")
                 gofumpt
                 golangci-lint
+                go-overlay.packages.${system}.govendor
                 nil
                 typos
               ]