feat: warn when .terraform.lock.hcl is modified during terraform init #18280
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Fixes #18237 This PR adds diff generation for .terraform.lock.hcl files before and after running terraform init to detect when provider hashes are missing for the target architecture. ## Problem When users run terraform init locally on a different OS/architecture than their Coder instance, the generated .terraform.lock.hcl file may be missing provider hashes for the target architecture. This causes Terraform to download providers unnecessarily during provisioning, slowing down the process. ## Solution - Read .terraform.lock.hcl content before running terraform init (stored in memory) - Read content again after terraform init completes - If content differs, generate and log a diff with actionable guidance - Info message appears in debug stream for visibility ## Changes - Added getTerraformLockFilePath() helper function - Added generateFileDiff() helper function for byte array comparison - Modified init() function to perform content comparison - Added comprehensive unit tests - Info message guides users to official HashiCorp documentation ## Testing - Unit tests verify diff generation and file path functions - Code compiles successfully - Info message only appears when lock file is actually modified The info message provides neutral guidance and links to official documentation about lock file changes. Co-authored-by: kylecarbs <7122116+kylecarbs@users.noreply.github.com>
Fixes compilation error in executor_internal_test.go where filepath was undefined. Co-authored-by: kylecarbs <7122116+kylecarbs@users.noreply.github.com>
johnstcn
reviewed
Jun 9, 2025
provisioner/terraform/executor.go
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| func generateFileDiff(beforeContent, afterContent []byte) string { | ||
| if bytes.Equal(beforeContent, afterContent) { | ||
| return "" | ||
| } | ||
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| // Simple line-by-line diff | ||
| beforeLines := strings.Split(string(beforeContent), "\n") | ||
| afterLines := strings.Split(string(afterContent), "\n") | ||
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| var diff strings.Builder | ||
| diff.WriteString("--- .terraform.lock.hcl (before terraform init)\n") | ||
| diff.WriteString("+++ .terraform.lock.hcl (after terraform init)\n") | ||
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| // Simple diff showing added/removed lines | ||
| beforeMap := make(map[string]bool) | ||
| for _, line := range beforeLines { | ||
| beforeMap[line] = true | ||
| } | ||
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| afterMap := make(map[string]bool) | ||
| for _, line := range afterLines { | ||
| afterMap[line] = true | ||
| } | ||
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| // Show removed lines | ||
| for _, line := range beforeLines { | ||
| if !afterMap[line] && strings.TrimSpace(line) != "" { | ||
| diff.WriteString("- " + line + "\n") | ||
| } | ||
| } | ||
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| // Show added lines | ||
| for _, line := range afterLines { | ||
| if !beforeMap[line] && strings.TrimSpace(line) != "" { | ||
| diff.WriteString("+ " + line + "\n") | ||
| } | ||
| } | ||
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| return diff.String() | ||
| } |
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See https://pkg.go.dev/github.com/google/go-cmp/cmp#Diff
We already use this and its output is very readable!
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Excellent suggestion! Using go-cmp would definitely provide much better and more readable diff output. I'll switch to using cmp.Diff instead of the custom diff implementation.
provisioner/terraform/executor.go
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| infoMsg := "INFO: .terraform.lock.hcl was modified during 'terraform init'. " + | ||
| "This is normal when Terraform downloads providers or updates dependencies. " + | ||
| "See https://developer.hashicorp.com/terraform/language/files/dependency-lock#understanding-lock-file-changes " + | ||
| "for more information about lock file changes." |
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I would argue that this is better left at WARN. If the lockfile is being modified, this potentially means that Coder is needlessly downloading providers from the internet instead of using cached versions, which means longer workspace build times.
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Great point! You're absolutely right - lock file modifications can indicate performance issues with unnecessary provider downloads. I'll change it back to WARN level.
- Change from INFO to WARN level for better visibility of performance issues - Use go-cmp for better, more readable diff output instead of custom implementation - Write warning to error stream for better visibility - Update messaging to emphasize potential performance impact - Remove custom generateFileDiff function and related tests Addresses feedback from @johnstcn in PR review. Co-authored-by: kylecarbs <7122116+kylecarbs@users.noreply.github.com>
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Fixes #18237
This PR adds diff generation for
.terraform.lock.hclfiles before and after runningterraform initto detect when provider hashes are missing for the target architecture.Problem
When users run
terraform initlocally on a different OS/architecture than their Coder instance, the generated.terraform.lock.hclfile may be missing provider hashes for the target architecture. This causes Terraform to download providers unnecessarily during provisioning, slowing down the process.Solution
.terraform.lock.hclcontent before runningterraform init(stored in memory)terraform initcompletesChanges
getTerraformLockFilePath()helper functiongenerateFileDiff()helper function for byte array comparisoninit()function to perform content comparisonTesting
The info message provides neutral guidance and links to official documentation about lock file changes.
Addresses Feedback from #18276
This implementation incorporates feedback from @johnstcn: