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[WIP] Extract magic constants from compiler_yaml.go to constants package #12703

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[WIP] Extract magic constants from compiler_yaml.go to constants package #12703

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Initial plan
Copilot Jan 30, 2026
52a4096
Add new semantic types and constants to constants package
Copilot Jan 30, 2026
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65 changes: 65 additions & 0 deletions pkg/constants/constants.go
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Original file line number Diff line number Diff line change
Expand Up @@ -225,12 +225,77 @@ func (e EngineName) IsValid() bool {
return len(e) > 0
}

// FilePath represents a file system path.
// This semantic type distinguishes file paths from arbitrary strings,
// making path parameters explicit and enabling future validation logic.
//
// Example usage:
//
// const PromptFilePath FilePath = "/tmp/gh-aw/aw-prompts/prompt.txt"
// func ReadFile(path FilePath) ([]byte, error) { ... }
type FilePath string

// String returns the string representation of the file path
func (f FilePath) String() string {
return string(f)
}

// IsValid returns true if the file path is non-empty
func (f FilePath) IsValid() bool {
return len(f) > 0
}

// ByteSize represents a size in bytes.
// This semantic type distinguishes byte sizes from arbitrary integers,
// making size parameters explicit and preventing accidental misuse.
//
// Example usage:
//
// const DefaultMaxPatchSize ByteSize = 1024
// func AllocateBuffer(size ByteSize) []byte { ... }
type ByteSize int

// String returns the string representation of the byte size
func (b ByteSize) String() string {
return fmt.Sprintf("%d", b)
}

// IsValid returns true if the byte size is non-negative
func (b ByteSize) IsValid() bool {
return b >= 0
}

// MaxExpressionLineLength is the maximum length for a single line expression before breaking into multiline.
const MaxExpressionLineLength LineLength = 120

// ExpressionBreakThreshold is the threshold for breaking long lines at logical points.
const ExpressionBreakThreshold LineLength = 100

// File path constants

// PromptFilePath is the file path where workflow prompts are written during compilation.
// This path is used in the agent job to store the final prompt content before execution.
const PromptFilePath FilePath = "/tmp/gh-aw/aw-prompts/prompt.txt"

// Size constants

// DefaultMaxPatchSize is the default maximum size (in KB) for patches in safe outputs.
// This limit applies to create_pull_request and push_to_pull_request_branch operations.
const DefaultMaxPatchSize ByteSize = 1024

// DefaultYAMLBuilderSize is the default initial capacity for YAML string builder (in bytes).
// Allocating 256KB upfront minimizes reallocations during workflow generation.
// Average workflow generates ~200KB, so 256KB provides adequate buffer.
const DefaultYAMLBuilderSize ByteSize = 256 * 1024

// MaxChunkSize is the maximum size for content chunks (in bytes) when splitting prompts.
// Set to 20900 bytes to stay under GitHub Actions' 21000-byte limit with a 100-byte buffer.
const MaxChunkSize ByteSize = 20900

// ChunkSizeBuffer is the buffer size (in bytes) reserved when calculating chunk limits.
// This ensures content doesn't exceed GitHub Actions' size constraints.
const ChunkSizeBuffer ByteSize = 100

// DefaultMCPRegistryURL is the default MCP registry URL.
const DefaultMCPRegistryURL URL = "https://api.mcp.github.com/v0.1"

Expand Down
78 changes: 78 additions & 0 deletions pkg/constants/constants_test.go
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Expand Up @@ -532,6 +532,84 @@ func TestSemanticTypeAliases(t *testing.T) {
t.Errorf("CustomEngine = %q, want %q", custom, "custom")
}
})

// Test FilePath type
t.Run("FilePath type", func(t *testing.T) {
var testPath FilePath = "/tmp/test/file.txt"
if string(testPath) != "/tmp/test/file.txt" {
t.Errorf("FilePath conversion failed: got %q, want %q", testPath, "/tmp/test/file.txt")
}

// Test PromptFilePath has the correct type
promptPath := PromptFilePath
if string(promptPath) != "/tmp/gh-aw/aw-prompts/prompt.txt" {
t.Errorf("PromptFilePath = %q, want %q", promptPath, "/tmp/gh-aw/aw-prompts/prompt.txt")
}

// Test IsValid
if !testPath.IsValid() {
t.Error("FilePath should be valid when non-empty")
}

var emptyPath FilePath = ""
if emptyPath.IsValid() {
t.Error("FilePath should be invalid when empty")
}

// Test String method
if testPath.String() != "/tmp/test/file.txt" {
t.Errorf("FilePath.String() = %q, want %q", testPath.String(), "/tmp/test/file.txt")
}
})

// Test ByteSize type
t.Run("ByteSize type", func(t *testing.T) {
var testSize ByteSize = 1024
if int(testSize) != 1024 {
t.Errorf("ByteSize conversion failed: got %d, want %d", testSize, 1024)
}

// Test size constants have the correct type
maxPatchSize := DefaultMaxPatchSize
if int(maxPatchSize) != 1024 {
t.Errorf("DefaultMaxPatchSize = %d, want %d", maxPatchSize, 1024)
}

yamlBuilderSize := DefaultYAMLBuilderSize
if int(yamlBuilderSize) != 256*1024 {
t.Errorf("DefaultYAMLBuilderSize = %d, want %d", yamlBuilderSize, 256*1024)
}

maxChunkSize := MaxChunkSize
if int(maxChunkSize) != 20900 {
t.Errorf("MaxChunkSize = %d, want %d", maxChunkSize, 20900)
}

chunkBuffer := ChunkSizeBuffer
if int(chunkBuffer) != 100 {
t.Errorf("ChunkSizeBuffer = %d, want %d", chunkBuffer, 100)
}

// Test IsValid
if !testSize.IsValid() {
t.Error("ByteSize should be valid when non-negative")
}

var zeroSize ByteSize = 0
if !zeroSize.IsValid() {
t.Error("ByteSize should be valid when zero")
}

var negativeSize ByteSize = -1
if negativeSize.IsValid() {
t.Error("ByteSize should be invalid when negative")
}

// Test String method
if testSize.String() != "1024" {
t.Errorf("ByteSize.String() = %q, want %q", testSize.String(), "1024")
}
})
}

func TestTypeSafetyBetweenSemanticTypes(t *testing.T) {
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5 changes: 3 additions & 2 deletions pkg/workflow/compiler_safe_outputs_config.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ import (
"encoding/json"
"fmt"

"github.com/githubnext/gh-aw/pkg/constants"
"github.com/githubnext/gh-aw/pkg/logger"
)

Expand Down Expand Up @@ -295,7 +296,7 @@ var handlerRegistry = map[string]handlerBuilder{
return nil
}
c := cfg.CreatePullRequests
maxPatchSize := 1024 // default 1024 KB
maxPatchSize := int(constants.DefaultMaxPatchSize) // default 1024 KB
if cfg.MaximumPatchSize > 0 {
maxPatchSize = cfg.MaximumPatchSize
}
Expand All @@ -319,7 +320,7 @@ var handlerRegistry = map[string]handlerBuilder{
return nil
}
c := cfg.PushToPullRequestBranch
maxPatchSize := 1024 // default 1024 KB
maxPatchSize := int(constants.DefaultMaxPatchSize) // default 1024 KB
if cfg.MaximumPatchSize > 0 {
maxPatchSize = cfg.MaximumPatchSize
}
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10 changes: 5 additions & 5 deletions pkg/workflow/compiler_yaml.go
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Expand Up @@ -176,7 +176,7 @@ func (c *Compiler) generateYAML(data *WorkflowData, markdownPath string) (string
// Pre-allocate builder capacity based on estimated workflow size
// Average workflow generates ~200KB, allocate 256KB to minimize reallocations
var yaml strings.Builder
yaml.Grow(256 * 1024)
yaml.Grow(int(constants.DefaultYAMLBuilderSize))

// Generate workflow header comments (including hash)
c.generateWorkflowHeader(&yaml, data, frontmatterHash)
Expand All @@ -198,8 +198,8 @@ func (c *Compiler) generateYAML(data *WorkflowData, markdownPath string) (string
}

func splitContentIntoChunks(content string) []string {
const maxChunkSize = 20900 // 21000 - 100 character buffer
const indentSpaces = " " // 10 spaces added to each line
const maxChunkSize = int(constants.MaxChunkSize) // 21000 - 100 character buffer
const indentSpaces = " " // 10 spaces added to each line

lines := strings.Split(content, "\n")
var chunks []string
Expand Down Expand Up @@ -278,13 +278,13 @@ func (c *Compiler) generatePrompt(yaml *strings.Builder, data *WorkflowData) {
// Validate that all placeholders have been substituted
yaml.WriteString(" - name: Validate prompt placeholders\n")
yaml.WriteString(" env:\n")
yaml.WriteString(" GH_AW_PROMPT: /tmp/gh-aw/aw-prompts/prompt.txt\n")
fmt.Fprintf(yaml, " GH_AW_PROMPT: %s\n", constants.PromptFilePath)
yaml.WriteString(" run: bash /opt/gh-aw/actions/validate_prompt_placeholders.sh\n")

// Print prompt (merged into prompt generation)
yaml.WriteString(" - name: Print prompt\n")
yaml.WriteString(" env:\n")
yaml.WriteString(" GH_AW_PROMPT: /tmp/gh-aw/aw-prompts/prompt.txt\n")
fmt.Fprintf(yaml, " GH_AW_PROMPT: %s\n", constants.PromptFilePath)
yaml.WriteString(" run: bash /opt/gh-aw/actions/print_prompt_summary.sh\n")
}

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2 changes: 1 addition & 1 deletion pkg/workflow/create_pull_request.go
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Expand Up @@ -87,7 +87,7 @@ func (c *Compiler) buildCreateOutputPullRequestJob(data *WorkflowData, mainJobNa
customEnvVars = append(customEnvVars, fmt.Sprintf(" GH_AW_PR_AUTO_MERGE: %q\n", fmt.Sprintf("%t", data.SafeOutputs.CreatePullRequests.AutoMerge)))

// Pass the maximum patch size configuration
maxPatchSize := 1024 // Default value
maxPatchSize := int(constants.DefaultMaxPatchSize) // Default value
if data.SafeOutputs != nil && data.SafeOutputs.MaximumPatchSize > 0 {
maxPatchSize = data.SafeOutputs.MaximumPatchSize
}
Expand Down