Supports switching default board

src/commands/board.rs

@@ -80,6 +80,15 @@ pub fn list_boards(project_dir: Option<&str>) -> Result<()> {
         "anvil board --add mega".bright_cyan()
     );
     if config.boards.len() > 1 {
+        println!(
+            "  Set default:    {}",
+            format!(
+                "anvil board --default {}",
+                config.boards.keys()
+                    .find(|k| *k != &config.build.default)
+                    .unwrap_or(&config.build.default)
+            ).bright_cyan()
+        );
         println!(
             "  Remove a board: {}",
             format!(
@@ -446,7 +455,7 @@ pub fn remove_board(name: &str, project_dir: Option<&str>) -> Result<()> {
     if name == config.build.default {
         bail!(
             "Cannot remove '{}' because it is the default board.\n  \
-             Change the default in .anvil.toml first, or remove a different board.",
+             Change the default first: anvil board --default <other-board>",
             name
         );
     }
@@ -495,6 +504,53 @@ pub fn remove_board(name: &str, project_dir: Option<&str>) -> Result<()> {
     Ok(())
 }
 
+/// Set the default board in .anvil.toml.
+pub fn set_default_board(name: &str, project_dir: Option<&str>) -> Result<()> {
+    let project_path = resolve_project_dir(project_dir)?;
+    let config = ProjectConfig::load(&project_path)?;
+
+    // Verify the board exists
+    if !config.boards.contains_key(name) {
+        let available: Vec<&String> = config.boards.keys().collect();
+        if available.is_empty() {
+            bail!(
+                "No board '{}' found.\n  \
+                 Add it first: anvil board --add {}",
+                name, name
+            );
+        } else {
+            bail!(
+                "No board '{}' found.\n  \
+                 Available: {}\n  \
+                 Add it first: anvil board --add {}",
+                name,
+                available.iter().map(|s| s.as_str()).collect::<Vec<_>>().join(", "),
+                name
+            );
+        }
+    }
+
+    let config_path = project_path.join(CONFIG_FILENAME);
+    let old = crate::project::config::set_default_in_file(&config_path, name)?;
+
+    let label = board_label(&config.boards[name].fqbn);
+    println!(
+        "{} Default board: {} ({})",
+        "ok".green(),
+        name.bright_white().bold(),
+        label.bright_cyan()
+    );
+    if !old.is_empty() && old != name {
+        println!(
+            "  {}",
+            format!("Changed from: {}", old).bright_black()
+        );
+    }
+    println!();
+
+    Ok(())
+}
+
 fn resolve_project_dir(project_dir: Option<&str>) -> Result<std::path::PathBuf> {
     let start = match project_dir {
         Some(dir) => std::path::PathBuf::from(dir),

src/main.rs

@@ -92,15 +92,19 @@ enum Commands {
         name: Option<String>,
 
         /// Add a board to the project
-        #[arg(long, conflicts_with_all = ["remove", "listall"])]
+        #[arg(long, conflicts_with_all = ["remove", "listall", "default"])]
         add: bool,
 
         /// Remove a board from the project
-        #[arg(long, conflicts_with_all = ["add", "listall"])]
+        #[arg(long, conflicts_with_all = ["add", "listall", "default"])]
         remove: bool,
 
+        /// Set the default board
+        #[arg(long, conflicts_with_all = ["add", "remove", "listall"])]
+        default: bool,
+
         /// Browse all available boards
-        #[arg(long, conflicts_with_all = ["add", "remove"])]
+        #[arg(long, conflicts_with_all = ["add", "remove", "default"])]
         listall: bool,
 
         /// Board identifier (from anvil board --listall)
@@ -177,7 +181,7 @@ fn main() -> Result<()> {
                 force,
             )
         }
-        Commands::Board { name, add, remove, listall, id, baud, dir } => {
+        Commands::Board { name, add, remove, default, listall, id, baud, dir } => {
             if listall {
                 commands::board::listall_boards(name.as_deref())
             } else if add {
@@ -205,6 +209,18 @@ fn main() -> Result<()> {
                     board_name,
                     dir.as_deref(),
                 )
+            } else if default {
+                let board_name = name.as_deref().ok_or_else(|| {
+                    anyhow::anyhow!(
+                        "Board name required.\n\
+                         Usage: anvil board --default uno\n\
+                         List boards: anvil board"
+                    )
+                })?;
+                commands::board::set_default_board(
+                    board_name,
+                    dir.as_deref(),
+                )
             } else {
                 commands::board::list_boards(dir.as_deref())
             }

src/project/config.rs

@@ -150,16 +150,23 @@ impl ProjectConfig {
 
         // Migrate old format: fqbn in [build] -> [boards.X] + default
         if config.build.default.is_empty() {
-            if let Some(legacy_fqbn) = config.build.fqbn.take() {
+            if let Some(ref legacy_fqbn) = config.build.fqbn {
                 let board_name = crate::board::presets::PRESETS.iter()
-                    .find(|p| p.fqbn == legacy_fqbn)
+                    .find(|p| p.fqbn == *legacy_fqbn)
                     .map(|p| p.name.to_string())
                     .unwrap_or_else(|| "default".to_string());
-                config.boards.entry(board_name.clone()).or_insert(BoardProfile {
+
-                    fqbn: legacy_fqbn,
+                // Text-based migration of the actual file
+                migrate_config_file(&config_path, &board_name, legacy_fqbn)?;
+
+                // Update in-memory config to match
+                let fqbn_clone = legacy_fqbn.clone();
+                config.build.fqbn = None;
+                config.build.default = board_name.clone();
+                config.boards.entry(board_name).or_insert(BoardProfile {
+                    fqbn: fqbn_clone,
                     baud: None,
                 });
-                config.build.default = board_name;
             }
         }
 
@@ -239,6 +246,138 @@ pub fn anvil_home() -> Result<PathBuf> {
     Ok(anvil_dir)
 }
 
+// -- Text-based .anvil.toml editing -----------------------------------------
+// These operate on the raw file text to preserve comments and formatting.
+
+/// Migrate an old-format config: add default = "X" to [build] and add
+/// [boards.X] section if needed. Keeps old fqbn line for backward
+/// compatibility with scripts that haven't been refreshed yet.
+fn migrate_config_file(config_path: &Path, board_name: &str, fqbn: &str) -> Result<()> {
+    let content = fs::read_to_string(config_path)
+        .context("Failed to read .anvil.toml for migration")?;
+
+    let mut output = String::new();
+    let mut in_build = false;
+    let mut added_default = false;
+    let mut has_board_section = false;
+
+    // Check if [boards.NAME] already exists
+    let section_header = format!("[boards.{}]", board_name);
+    for line in content.lines() {
+        if line.trim() == section_header {
+            has_board_section = true;
+            break;
+        }
+    }
+
+    for line in content.lines() {
+        let trimmed = line.trim();
+
+        // Track which section we're in
+        if trimmed == "[build]" {
+            in_build = true;
+            output.push_str(line);
+            output.push('\n');
+            continue;
+        }
+        if trimmed.starts_with('[') && trimmed != "[build]" {
+            // Leaving [build] -- add default before leaving if we haven't yet
+            if in_build && !added_default {
+                output.push_str(&format!("default = \"{}\"\n", board_name));
+                added_default = true;
+            }
+            in_build = false;
+        }
+
+        // In [build]: add default right before fqbn (natural reading order)
+        if in_build && !added_default && trimmed.starts_with("fqbn") && trimmed.contains('=') {
+            output.push_str(&format!("default = \"{}\"\n", board_name));
+            added_default = true;
+        }
+
+        output.push_str(line);
+        output.push('\n');
+    }
+
+    // Add [boards.NAME] section if it doesn't already exist
+    if !has_board_section {
+        while output.ends_with("\n\n") {
+            output.pop();
+        }
+        output.push('\n');
+        output.push_str(&format!("\n[boards.{}]\n", board_name));
+        output.push_str(&format!("fqbn = \"{}\"\n", fqbn));
+    }
+
+    fs::write(config_path, &output)
+        .context("Failed to write migrated .anvil.toml")?;
+
+    eprintln!(
+        "\x1b[33minfo\x1b[0m  Migrated .anvil.toml: default = \"{}\"{}",
+        board_name,
+        if has_board_section { "" } else { ", added [boards] section" }
+    );
+    eprintln!(
+        "\x1b[33minfo\x1b[0m  Run \x1b[36manvil refresh --force\x1b[0m to update scripts."
+    );
+
+    Ok(())
+}
+
+/// Set or change the default board in .anvil.toml (text-based edit).
+/// Returns the old default name (empty string if there wasn't one).
+pub fn set_default_in_file(config_path: &Path, board_name: &str) -> Result<String> {
+    let content = fs::read_to_string(config_path)
+        .context("Failed to read .anvil.toml")?;
+
+    let mut output = String::new();
+    let mut in_build = false;
+    let mut replaced = false;
+    let mut old_default = String::new();
+
+    for line in content.lines() {
+        let trimmed = line.trim();
+
+        if trimmed == "[build]" {
+            in_build = true;
+            output.push_str(line);
+            output.push('\n');
+            continue;
+        }
+        if trimmed.starts_with('[') && trimmed != "[build]" {
+            // Leaving [build] without having found default -- add it
+            if in_build && !replaced {
+                output.push_str(&format!("default = \"{}\"\n", board_name));
+                replaced = true;
+            }
+            in_build = false;
+        }
+
+        if in_build && trimmed.starts_with("default") && trimmed.contains('=') {
+            // Extract old value
+            if let Some(val) = trimmed.split('=').nth(1) {
+                old_default = val.trim().trim_matches('"').to_string();
+            }
+            output.push_str(&format!("default = \"{}\"\n", board_name));
+            replaced = true;
+            continue;
+        }
+
+        output.push_str(line);
+        output.push('\n');
+    }
+
+    // Edge case: [build] was the last section and had no default
+    if in_build && !replaced {
+        output.push_str(&format!("default = \"{}\"\n", board_name));
+    }
+
+    fs::write(config_path, &output)
+        .context("Failed to write .anvil.toml")?;
+
+    Ok(old_default)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -382,4 +521,105 @@ mod tests {
         assert_eq!(mega.fqbn, "arduino:avr:mega:cpu=atmega2560");
         assert_eq!(mega.baud, Some(57600));
     }
+
+    #[test]
+    fn test_migrate_old_format() {
+        let tmp = TempDir::new().unwrap();
+        let old_config = r#"[project]
+name = "hand"
+anvil_version = "1.0.0"
+
+[build]
+fqbn = "arduino:avr:uno"
+warnings = "more"
+include_dirs = ["lib/hal", "lib/app"]
+extra_flags = ["-Werror"]
+
+[monitor]
+baud = 115200
+
+[boards.micro]
+fqbn = "arduino:avr:micro"
+"#;
+        fs::write(tmp.path().join(CONFIG_FILENAME), old_config).unwrap();
+
+        let config = ProjectConfig::load(tmp.path()).unwrap();
+        assert_eq!(config.build.default, "uno");
+        assert!(config.boards.contains_key("uno"));
+        assert_eq!(config.boards["uno"].fqbn, "arduino:avr:uno");
+        assert!(config.boards.contains_key("micro"));
+
+        // Verify the file was rewritten
+        let content = fs::read_to_string(tmp.path().join(CONFIG_FILENAME)).unwrap();
+        assert!(content.contains("default = \"uno\""));
+        assert!(content.contains("[boards.uno]"));
+        // Old fqbn stays in [build] for backward compat with old scripts
+        assert!(content.contains("fqbn = \"arduino:avr:uno\""));
+    }
+
+    #[test]
+    fn test_migrate_preserves_existing_boards() {
+        let tmp = TempDir::new().unwrap();
+        let old_config = r#"[project]
+name = "test"
+anvil_version = "1.0.0"
+
+[build]
+fqbn = "arduino:avr:mega:cpu=atmega2560"
+warnings = "more"
+include_dirs = ["lib/hal", "lib/app"]
+extra_flags = ["-Werror"]
+
+[monitor]
+baud = 115200
+"#;
+        fs::write(tmp.path().join(CONFIG_FILENAME), old_config).unwrap();
+
+        let config = ProjectConfig::load(tmp.path()).unwrap();
+        assert_eq!(config.build.default, "mega");
+        assert!(config.boards.contains_key("mega"));
+    }
+
+    #[test]
+    fn test_set_default_in_file() {
+        let tmp = TempDir::new().unwrap();
+        let config = ProjectConfig::new("test");
+        config.save(tmp.path()).unwrap();
+
+        let config_path = tmp.path().join(CONFIG_FILENAME);
+        let old = set_default_in_file(&config_path, "mega").unwrap();
+        assert_eq!(old, "uno");
+
+        let content = fs::read_to_string(&config_path).unwrap();
+        assert!(content.contains("default = \"mega\""));
+        assert!(!content.contains("default = \"uno\""));
+    }
+
+    #[test]
+    fn test_set_default_adds_when_missing() {
+        let tmp = TempDir::new().unwrap();
+        let content = r#"[project]
+name = "test"
+anvil_version = "1.0.0"
+
+[build]
+warnings = "more"
+include_dirs = ["lib/hal", "lib/app"]
+extra_flags = ["-Werror"]
+
+[monitor]
+baud = 115200
+
+[boards.uno]
+fqbn = "arduino:avr:uno"
+"#;
+        let config_path = tmp.path().join(CONFIG_FILENAME);
+        fs::write(&config_path, content).unwrap();
+
+        let old = set_default_in_file(&config_path, "uno").unwrap();
+        assert_eq!(old, "");
+
+        let result = fs::read_to_string(&config_path).unwrap();
+        assert!(result.contains("default = \"uno\""));
+    }
 }

templates/basic/build.bat

@@ -70,6 +70,22 @@ exit /b 0
 :: -- Resolve board --------------------------------------------------------
 if "%BOARD_NAME%"=="" set "BOARD_NAME=%DEFAULT_BOARD%"
 
+if "%BOARD_NAME%"=="" (
+    echo FAIL: No default board set in .anvil.toml.
+    echo.
+    echo   Add a default to the [build] section of .anvil.toml:
+    echo     default = "uno"
+    echo.
+    echo   And make sure a matching [boards.uno] section exists:
+    echo     [boards.uno]
+    echo     fqbn = "arduino:avr:uno"
+    echo.
+    echo   Or with Anvil:  anvil board --default uno
+    echo   List boards:    anvil board --listall
+    echo                   arduino-cli board listall
+    exit /b 1
+)
+
 set "BOARD_SECTION=[boards.%BOARD_NAME%]"
 set "IN_SECTION=0"
 set "FQBN="
@@ -96,8 +112,15 @@ for /f "usebackq tokens=*" %%L in ("%CONFIG%") do (
 )
 
 if "!FQBN!"=="" (
-    echo FAIL: No board '%BOARD_NAME%' in .anvil.toml.
+    echo FAIL: No [boards.%BOARD_NAME%] section in .anvil.toml.
-    echo   Add it: anvil board --add %BOARD_NAME%
+    echo.
+    echo   Add it to .anvil.toml:
+    echo     [boards.%BOARD_NAME%]
+    echo     fqbn = "arduino:avr:uno"    ^(replace with your board^)
+    echo.
+    echo   Or with Anvil:  anvil board --add %BOARD_NAME%
+    echo   List boards:    anvil board --listall
+    echo                   arduino-cli board listall
     exit /b 1
 )
 

templates/basic/build.sh

@@ -87,10 +87,35 @@ done
 
 # -- Resolve board ---------------------------------------------------------
 ACTIVE_BOARD="${BOARD_NAME:-$DEFAULT_BOARD}"
+
+if [[ -z "$ACTIVE_BOARD" ]]; then
+    echo "${RED}FAIL${RST} No default board set in .anvil.toml." >&2
+    echo "" >&2
+    echo "  Add a default to the [build] section of .anvil.toml:" >&2
+    echo "    default = \"uno\"" >&2
+    echo "" >&2
+    echo "  And make sure a matching [boards.uno] section exists:" >&2
+    echo "    [boards.uno]" >&2
+    echo "    fqbn = \"arduino:avr:uno\"" >&2
+    echo "" >&2
+    echo "  Or with Anvil:  anvil board --default uno" >&2
+    echo "  List boards:    anvil board --listall" >&2
+    echo "                  arduino-cli board listall" >&2
+    exit 1
+fi
 FQBN="$(toml_section_get "boards.$ACTIVE_BOARD" "fqbn")"
 
 if [[ -z "$FQBN" ]]; then
-    die "No board '$ACTIVE_BOARD' in .anvil.toml.\n  Add it: anvil board --add $ACTIVE_BOARD"
+    echo "${RED}FAIL${RST} No [boards.$ACTIVE_BOARD] section in .anvil.toml." >&2
+    echo "" >&2
+    echo "  Add it to .anvil.toml:" >&2
+    echo "    [boards.$ACTIVE_BOARD]" >&2
+    echo "    fqbn = \"arduino:avr:uno\"    # replace with your board" >&2
+    echo "" >&2
+    echo "  Or with Anvil:  anvil board --add $ACTIVE_BOARD" >&2
+    echo "  List boards:    anvil board --listall" >&2
+    echo "                  arduino-cli board listall" >&2
+    exit 1
 fi
 
 if [[ -n "$BOARD_NAME" ]]; then

templates/basic/monitor.bat

@@ -84,6 +84,22 @@ exit /b 0
 :: -- Resolve board --------------------------------------------------------
 if "%BOARD_NAME%"=="" set "BOARD_NAME=%DEFAULT_BOARD%"
 
+if "%BOARD_NAME%"=="" (
+    echo FAIL: No default board set in .anvil.toml.
+    echo.
+    echo   Add a default to the [build] section of .anvil.toml:
+    echo     default = "uno"
+    echo.
+    echo   And make sure a matching [boards.uno] section exists:
+    echo     [boards.uno]
+    echo     fqbn = "arduino:avr:uno"
+    echo.
+    echo   Or with Anvil:  anvil board --default uno
+    echo   List boards:    anvil board --listall
+    echo                   arduino-cli board listall
+    exit /b 1
+)
+
 set "BOARD_SECTION=[boards.%BOARD_NAME%]"
 set "IN_SECTION=0"
 set "BOARD_BAUD="

templates/basic/monitor.sh

@@ -82,6 +82,22 @@ done
 
 # -- Resolve board ---------------------------------------------------------
 ACTIVE_BOARD="${BOARD_NAME:-$DEFAULT_BOARD}"
+
+if [[ -z "$ACTIVE_BOARD" ]]; then
+    echo "${RED}FAIL${RST} No default board set in .anvil.toml." >&2
+    echo "" >&2
+    echo "  Add a default to the [build] section of .anvil.toml:" >&2
+    echo "    default = \"uno\"" >&2
+    echo "" >&2
+    echo "  And make sure a matching [boards.uno] section exists:" >&2
+    echo "    [boards.uno]" >&2
+    echo "    fqbn = \"arduino:avr:uno\"" >&2
+    echo "" >&2
+    echo "  Or with Anvil:  anvil board --default uno" >&2
+    echo "  List boards:    anvil board --listall" >&2
+    echo "                  arduino-cli board listall" >&2
+    exit 1
+fi
 BOARD_BAUD="$(toml_section_get "boards.$ACTIVE_BOARD" "baud")"
 if [[ -n "$BOARD_BAUD" ]]; then
     BAUD="$BOARD_BAUD"

templates/basic/upload.bat

@@ -99,6 +99,22 @@ exit /b 0
 :: -- Resolve board --------------------------------------------------------
 if "%BOARD_NAME%"=="" set "BOARD_NAME=%DEFAULT_BOARD%"
 
+if "%BOARD_NAME%"=="" (
+    echo FAIL: No default board set in .anvil.toml.
+    echo.
+    echo   Add a default to the [build] section of .anvil.toml:
+    echo     default = "uno"
+    echo.
+    echo   And make sure a matching [boards.uno] section exists:
+    echo     [boards.uno]
+    echo     fqbn = "arduino:avr:uno"
+    echo.
+    echo   Or with Anvil:  anvil board --default uno
+    echo   List boards:    anvil board --listall
+    echo                   arduino-cli board listall
+    exit /b 1
+)
+
 set "BOARD_SECTION=[boards.%BOARD_NAME%]"
 set "IN_SECTION=0"
 set "FQBN="
@@ -127,8 +143,15 @@ for /f "usebackq tokens=*" %%L in ("%CONFIG%") do (
 )
 
 if "!FQBN!"=="" (
-    echo FAIL: No board '%BOARD_NAME%' in .anvil.toml.
+    echo FAIL: No [boards.%BOARD_NAME%] section in .anvil.toml.
-    echo   Add it: anvil board --add %BOARD_NAME%
+    echo.
+    echo   Add it to .anvil.toml:
+    echo     [boards.%BOARD_NAME%]
+    echo     fqbn = "arduino:avr:uno"    ^(replace with your board^)
+    echo.
+    echo   Or with Anvil:  anvil board --add %BOARD_NAME%
+    echo   List boards:    anvil board --listall
+    echo                   arduino-cli board listall
     exit /b 1
 )
 if not "!BOARD_BAUD!"=="" set "BAUD=!BOARD_BAUD!"

templates/basic/upload.sh

@@ -101,10 +101,35 @@ done
 
 # -- Resolve board ---------------------------------------------------------
 ACTIVE_BOARD="${BOARD_NAME:-$DEFAULT_BOARD}"
+
+if [[ -z "$ACTIVE_BOARD" ]]; then
+    echo "${RED}FAIL${RST} No default board set in .anvil.toml." >&2
+    echo "" >&2
+    echo "  Add a default to the [build] section of .anvil.toml:" >&2
+    echo "    default = \"uno\"" >&2
+    echo "" >&2
+    echo "  And make sure a matching [boards.uno] section exists:" >&2
+    echo "    [boards.uno]" >&2
+    echo "    fqbn = \"arduino:avr:uno\"" >&2
+    echo "" >&2
+    echo "  Or with Anvil:  anvil board --default uno" >&2
+    echo "  List boards:    anvil board --listall" >&2
+    echo "                  arduino-cli board listall" >&2
+    exit 1
+fi
 FQBN="$(toml_section_get "boards.$ACTIVE_BOARD" "fqbn")"
 
 if [[ -z "$FQBN" ]]; then
-    die "No board '$ACTIVE_BOARD' in .anvil.toml.\n  Add it: anvil board --add $ACTIVE_BOARD"
+    echo "${RED}FAIL${RST} No [boards.$ACTIVE_BOARD] section in .anvil.toml." >&2
+    echo "" >&2
+    echo "  Add it to .anvil.toml:" >&2
+    echo "    [boards.$ACTIVE_BOARD]" >&2
+    echo "    fqbn = \"arduino:avr:uno\"    # replace with your board" >&2
+    echo "" >&2
+    echo "  Or with Anvil:  anvil board --add $ACTIVE_BOARD" >&2
+    echo "  List boards:    anvil board --listall" >&2
+    echo "                  arduino-cli board listall" >&2
+    exit 1
 fi
 
 BOARD_BAUD="$(toml_section_get "boards.$ACTIVE_BOARD" "baud")"