Wrap all errors with context using fmt.Errorf (#170)

* Initial plan

* Improve error handling with clear context and wrapped errors

Co-authored-by: alexec <1142830+alexec@users.noreply.github.com>

* Apply code review suggestions: improve error messages consistency and context

Co-authored-by: alexec <1142830+alexec@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: alexec <1142830+alexec@users.noreply.github.com>

Author: Copilot

pkg/codingcontext/agent.go

@@ -101,7 +101,7 @@ var agentPathPatterns = map[Agent][]string{
 func (a *Agent) Set(value string) error {
 	agent, err := ParseAgent(value)
 	if err != nil {
-		return err
+		return fmt.Errorf("failed to set agent value %q: %w", value, err)
 	}
 
 	*a = agent

pkg/codingcontext/context.go

@@ -67,12 +67,12 @@ func (cc *Context) visitMarkdownFiles(searchDirFn func(path string) []string, vi
 		if _, err := os.Stat(dir); os.IsNotExist(err) {
 			continue
 		} else if err != nil {
-			return err
+			return fmt.Errorf("failed to stat directory %s: %w", dir, err)
 		}
 
 		err := filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
 			if err != nil {
-				return err
+				return fmt.Errorf("failed to walk path %s: %w", path, err)
 			}
 			ext := filepath.Ext(path) // .md or .mdc
 			if info.IsDir() || ext != ".md" && ext != ".mdc" {
@@ -94,7 +94,7 @@ func (cc *Context) visitMarkdownFiles(searchDirFn func(path string) []string, vi
 			return visitor(path)
 		})
 		if err != nil {
-			return err
+			return fmt.Errorf("failed to walk directory %s: %w", dir, err)
 		}
 	}
 
@@ -118,7 +118,7 @@ func (cc *Context) findTask(taskName string) error {
 		var frontMatter markdown.TaskFrontMatter
 		md, err := markdown.ParseMarkdownFile(path, &frontMatter)
 		if err != nil {
-			return err
+			return fmt.Errorf("failed to parse task file %s: %w", path, err)
 		}
 
 		// Extract selector labels from task frontmatter and add them to cc.includes.
@@ -132,7 +132,7 @@ func (cc *Context) findTask(taskName string) error {
 		if frontMatter.Agent != "" {
 			agent, err := ParseAgent(frontMatter.Agent)
 			if err != nil {
-				return err
+				return fmt.Errorf("failed to parse agent from task frontmatter: %w", err)
 			}
 			cc.agent = agent
 		}
@@ -152,7 +152,7 @@ func (cc *Context) findTask(taskName string) error {
 		// Parse the task content (including user_prompt) to separate text blocks from slash commands
 		task, err := taskparser.ParseTask(taskContent)
 		if err != nil {
-			return err
+			return fmt.Errorf("failed to parse task content: %w", err)
 		}
 
 		// Build the final content by processing each block
@@ -174,7 +174,7 @@ func (cc *Context) findTask(taskName string) error {
 			} else if block.SlashCommand != nil {
 				commandContent, err := cc.findCommand(block.SlashCommand.Name, block.SlashCommand.Params())
 				if err != nil {
-					return err
+					return fmt.Errorf("failed to find command %s: %w", block.SlashCommand.Name, err)
 				}
 				finalContent.WriteString(commandContent)
 			}
@@ -218,7 +218,7 @@ func (cc *Context) findCommand(commandName string, params taskparser.Params) (st
 		var frontMatter markdown.CommandFrontMatter
 		md, err := markdown.ParseMarkdownFile(path, &frontMatter)
 		if err != nil {
-			return err
+			return fmt.Errorf("failed to parse command file %s: %w", path, err)
 		}
 
 		// Extract selector labels from command frontmatter and add them to cc.includes.

pkg/codingcontext/markdown/frontmatter.go

@@ -2,6 +2,7 @@ package markdown
 
 import (
 	"encoding/json"
+	"fmt"
 
 	"github.com/kitproj/coding-context-cli/pkg/codingcontext/mcp"
 )
@@ -57,12 +58,12 @@ func (t *TaskFrontMatter) UnmarshalJSON(data []byte) error {
 	}
 
 	if err := json.Unmarshal(data, aux); err != nil {
-		return err
+		return fmt.Errorf("failed to unmarshal task frontmatter: %w", err)
 	}
 
 	// Also unmarshal into Content map
 	if err := json.Unmarshal(data, &t.BaseFrontMatter.Content); err != nil {
-		return err
+		return fmt.Errorf("failed to unmarshal task frontmatter content: %w", err)
 	}
 
 	return nil
@@ -94,12 +95,12 @@ func (c *CommandFrontMatter) UnmarshalJSON(data []byte) error {
 	}
 
 	if err := json.Unmarshal(data, aux); err != nil {
-		return err
+		return fmt.Errorf("failed to unmarshal command frontmatter: %w", err)
 	}
 
 	// Also unmarshal into Content map
 	if err := json.Unmarshal(data, &c.BaseFrontMatter.Content); err != nil {
-		return err
+		return fmt.Errorf("failed to unmarshal command frontmatter content: %w", err)
 	}
 
 	return nil
@@ -143,12 +144,12 @@ func (r *RuleFrontMatter) UnmarshalJSON(data []byte) error {
 	}
 
 	if err := json.Unmarshal(data, aux); err != nil {
-		return err
+		return fmt.Errorf("failed to unmarshal rule frontmatter: %w", err)
 	}
 
 	// Also unmarshal into Content map
 	if err := json.Unmarshal(data, &r.BaseFrontMatter.Content); err != nil {
-		return err
+		return fmt.Errorf("failed to unmarshal rule frontmatter content: %w", err)
 	}
 
 	return nil

pkg/codingcontext/mcp/mcp.go

@@ -1,6 +1,9 @@
 package mcp
 
-import "encoding/json"
+import (
+	"encoding/json"
+	"fmt"
+)
 
 // TransportType defines the communication protocol used by the server.
 // Supported by both Claude and Cursor.
@@ -58,7 +61,7 @@ func (m *MCPServerConfig) UnmarshalJSON(data []byte) error {
 	}
 
 	if err := json.Unmarshal(data, aux); err != nil {
-		return err
+		return fmt.Errorf("failed to unmarshal MCP server config: %w", err)
 	}
 
 	// Initialize Content map if needed
@@ -68,7 +71,7 @@ func (m *MCPServerConfig) UnmarshalJSON(data []byte) error {
 
 	// Also unmarshal into Content map
 	if err := json.Unmarshal(data, &m.Content); err != nil {
-		return err
+		return fmt.Errorf("failed to unmarshal MCP server config content: %w", err)
 	}
 
 	return nil

pkg/codingcontext/taskparser/params.go

@@ -377,7 +377,7 @@ func (p Params) Set(value string) error {
 
 	params, err := ParseParams(quotedValue)
 	if err != nil {
-		return err
+		return fmt.Errorf("failed to parse parameter '%s': %w", value, err)
 	}
 
 	maps.Copy(p, params)