chore: add github action to check diffs on generated bits

For now, we're checking the diff of:
    go mod tidy
    make fmt

.github/workflows/make-gen-delta.yml

@@ -0,0 +1,42 @@
+name: "make-gen-delta"
+on:
+  - workflow_dispatch
+  - push
+  - workflow_call
+
+permissions:
+  contents: read
+
+jobs:
+  make-gen-delta:
+    name: "Check for uncommitted changes from make gen"
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3.5.3
+        with:
+          fetch-depth: '0'
+      - name: Determine Go version
+        id: get-go-version
+        # We use .go-version as our source of truth for current Go
+        # version, because "goenv" can react to it automatically.
+        run: |
+          echo "Building with Go $(cat .go-version)"
+          echo "go-version=$(cat .go-version)" >> "$GITHUB_OUTPUT"
+      - name: Set up Go
+        uses: actions/setup-go@93397bea11091df50f3d7e59dc26a7711a8bcfbe # v4.1.0
+        with:
+          go-version: "${{ steps.get-go-version.outputs.go-version }}"
+      - name: Running go mod tidy
+        run: |
+          go mod tidy
+      - name: Install Dependencies
+        run: |
+          make tools
+      - name: Running make fmt
+        run: |
+          make fmt
+      - name: Check for changes
+        run: |
+          git diff --exit-code
+          git status --porcelain
+          test -z "$(git status --porcelain)"

Makefile

@@ -42,3 +42,7 @@ coverage:
 	cd coverage && \
 	./coverage.sh && \
 	if ./cov-diff.sh ./coverage.log; then git restore coverage.log; fi
+
+.PHONY: tools
+tools:
+	go generate -tags tools tools/tools.go

expr.go

@@ -130,9 +130,7 @@ const (
 func newLogicalOp(s string) (logicalOp, error) {
 	const op = "newLogicalOp"
 	switch logicalOp(s) {
-	case
-		andOp,
-		orOp:
+	case andOp, orOp:
 		return logicalOp(s), nil
 	default:
 		return "", fmt.Errorf("%s: %w %q", op, ErrInvalidLogicalOp, s)

lex_test.go

@@ -388,7 +388,6 @@ func Test_lexWhitespaceState(t *testing.T) {
 			assert.Equal(tc.want, tk)
 		})
 	}
-
 }
 
 // Fuzz_lexerNextToken is only focused on finding panics

mql_unexported_test.go

@@ -158,6 +158,7 @@ type invalidExpr struct{}
 func (*invalidExpr) Type() exprType {
 	return unknownExprType
 }
+
 func (*invalidExpr) String() string {
 	return "unknown"
 }

tools/tools.go

@@ -0,0 +1,24 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+//go:build tools
+// +build tools
+
+// This file ensures tool dependencies are kept in sync.  This is the
+// recommended way of doing this according to
+// https://github.com/golang/go/wiki/Modules#how-can-i-track-tool-dependencies-for-a-module
+// To install the following tools at the version used by this repo run:
+// $ make tools
+// or
+// $ go generate -tags tools tools/tools.go
+
+package tools
+
+// NOTE: This must not be indented, so to stop goimports from trying to be
+// helpful, it's separated out from the import block below. Please try to keep
+// them in the same order.
+//go:generate go install mvdan.cc/gofumpt
+
+import (
+	_ "mvdan.cc/gofumpt"
+)