Implement automatic Go version chaining for bootstrapping

README.md

@@ -62,42 +62,17 @@ Additional options can be specified when installing Go:
         -h,  --help               Display this message.
 
 ### A Note on Compiling Go 1.5+
-Go 1.5+ removed the C compilers from the toolchain and [replaced][compiler_note] them with one written in Go. Obviously, this creates a bootstrapping problem if you don't already have a working Go install. In order to compile Go 1.5+, make sure Go 1.4 is installed first. If Go 1.4 won't install try a later version (e.g. go1.5), just make sure you have the `-B` option after the version number. 
+Go 1.5+ removed the C compilers from the toolchain and replaced them with one written in Go. GVM handles this bootstrapping problem automatically. When you install a version of Go from source that requires a bootstrap compiler, GVM will:
 
-```
-gvm install go1.4 -B
-gvm use go1.4
-export GOROOT_BOOTSTRAP=$GOROOT
-gvm install go1.7
-```
-
-### A Note on ARMv6 and ARMv7 architectures (32 bit)
-Binary versions for ARMv6 architecture are available [starting from Go 1.6](https://go.dev/dl/#go1.6). So, it is necessary to bootstrap with an existing binary version, then it will be possible compiling other versions. For instance, to bootstrap a setup, version `1.21.0` may be used:
-
-```
-gvm install go1.21.0 -B
-gvm use go1.21.0
-```
+1.  Search your installed versions for a compatible bootstrap Go.
+2.  If none is found, it will automatically download and install the required bootstrap version as a binary.
+3.  Use that binary to compile your target version.
 
-And then, compile any other version:
+This allows you to install any version of Go (including `master`) on a clean system without any pre-existing Go installation.
 
-```
-gvm install go1.20.7
-```
-
-#### To install Go 1.20+
-Go 1.20+ requires go1.17.3+. Use the below:
+### A Note on ARMv6 and ARMv7 architectures (32 bit)
+Binary versions for ARMv6 architecture are available [starting from Go 1.6](https://go.dev/dl/#go1.6). GVM will automatically pull a compatible binary to bootstrap source installations on ARM platforms as well.
 
-```
-gvm install go1.4 -B
-gvm use go1.4
-export GOROOT_BOOTSTRAP=$GOROOT
-gvm install go1.17.13
-gvm use go1.17.13
-export GOROOT_BOOTSTRAP=$GOROOT
-gvm install go1.20
-gvm use go1.20
-```
 
 [compiler_note]: https://docs.google.com/document/d/1OaatvGhEAq7VseQ9kkavxKNAfepWy2yhPUBs96FGV28/edit
 

scripts/function/gvm_bootstrap

@@ -0,0 +1,154 @@
+#!/usr/bin/env bash
+
+__gvm_get_required_bootstrap_version() {
+    local version=$1
+    if [[ "$version" == "master" ]]; then
+        echo "1.22.6"
+        return 0
+    fi
+
+    local semver=$(extract_version "$version")
+
+    # Check for non-numeric versions (like tip, etc)
+    if [[ ! "$semver" =~ ^[0-9]+(\.[0-9]+)*$ ]]; then
+        # Default to latest bootstrap for unknown versions
+        echo "1.22.6"
+        return 0
+    fi
+
+    # Go 1.24+ needs Go 1.22.6+
+    compare_version "$semver" "1.24"
+    if [[ $? -ne 2 ]]; then
+        echo "1.22.6"
+        return 0
+    fi
+
+    # Go 1.22+ needs Go 1.20+
+    compare_version "$semver" "1.22"
+    if [[ $? -ne 2 ]]; then
+        echo "1.20.14"
+        return 0
+    fi
+
+    # Go 1.20+ needs Go 1.17.13+
+    compare_version "$semver" "1.20"
+    if [[ $? -ne 2 ]]; then
+        echo "1.17.13"
+        return 0
+    fi
+
+    # Go 1.5+ needs Go 1.4+
+    compare_version "$semver" "1.5"
+    if [[ $? -ne 2 ]]; then
+        echo "1.4.3"
+        return 0
+    fi
+
+    echo ""
+    return 1
+}
+
+__gvm_find_best_installed_bootstrap() {
+    local min_version=$1
+    local best_version=""
+    local best_semver=""
+
+    if [[ ! -d "$GVM_ROOT/gos" ]]; then
+        return 1
+    fi
+
+    for v_dir in "$GVM_ROOT/gos"/*; do
+        [[ -d "$v_dir" ]] || continue
+        [[ -x "$v_dir/bin/go" ]] || continue
+        local v_name=$(basename "$v_dir")
+        local v_semver=$(extract_version "$v_name")
+
+        # Only consider numeric versions
+        if [[ ! "$v_semver" =~ ^[0-9]+(\.[0-9]+)*$ ]]; then
+            continue
+        fi
+
+        compare_version "$v_semver" "$min_version"
+        if [[ $? -ne 2 ]]; then # v_semver >= min_version
+            if [[ -z "$best_version" ]]; then
+                best_version=$v_name
+                best_semver=$v_semver
+            else
+                compare_version "$v_semver" "$best_semver"
+                if [[ $? -eq 1 ]]; then # v_semver > best_semver
+                    best_version=$v_name
+                    best_semver=$v_semver
+                fi
+            fi
+        fi
+    done
+
+    if [[ -n "$best_version" ]]; then
+        echo "$best_version"
+        return 0
+    fi
+    return 1
+}
+
+__gvm_is_bootstrap_compatible() {
+    local target=$1
+    local bootstrap_path=$2
+
+    local req_version=$(__gvm_get_required_bootstrap_version "$target")
+    if [[ -z "$req_version" ]]; then
+        return 0 # No bootstrap needed
+    fi
+
+    if [[ -z "$bootstrap_path" ]]; then
+        return 1 # No bootstrap path provided
+    fi
+
+    if [[ ! -x "$bootstrap_path/bin/go" ]]; then
+        return 1 # Bootstrap path doesn't have a working go
+    fi
+
+    # Try to get the version of the bootstrap Go
+    local bootstrap_version_out=$("$bootstrap_path/bin/go" version 2>/dev/null)
+    if [[ $? -ne 0 ]]; then
+        return 1
+    fi
+
+    # Extract version from "go version go1.22.6 linux/amd64"
+    local bootstrap_version=$(echo "$bootstrap_version_out" | awk '{print $3}')
+    local bootstrap_semver=$(extract_version "$bootstrap_version")
+
+    compare_version "$bootstrap_semver" "$req_version"
+    if [[ $? -ne 2 ]]; then
+        return 0 # Compatible (>=)
+    fi
+
+    return 1 # Incompatible (<)
+}
+
+__gvm_ensure_bootstrap() {
+    local target_version=$1
+    local req_version=$(__gvm_get_required_bootstrap_version "$target_version")
+
+    if [[ -z "$req_version" ]]; then
+        return 0
+    fi
+
+    local bootstrap_version=$(__gvm_find_best_installed_bootstrap "$req_version")
+
+    if [[ -n "$bootstrap_version" ]]; then
+        export GOROOT_BOOTSTRAP="$GVM_ROOT/gos/$bootstrap_version"
+        display_message "Using $bootstrap_version as bootstrap"
+        return 0
+    fi
+
+    display_message "No suitable bootstrap Go version found. Installing go$req_version binary..."
+
+    # Use the absolute path to gvm to ensure we use the right one
+    "$GVM_ROOT/bin/gvm" install "go$req_version" --binary || {
+        display_error "Failed to install bootstrap Go version go$req_version"
+        return 1
+    }
+
+    export GOROOT_BOOTSTRAP="$GVM_ROOT/gos/go$req_version"
+    return 0
+}

scripts/install

@@ -90,7 +90,13 @@ compile_go() {
 		MAKE_SCRIPT=make.bash
 		;;
 	esac
-	[ -z "$GOROOT_BOOTSTRAP" ] && export GOROOT_BOOTSTRAP=$(go env GOROOT) 
+
+	[ -z "$GOROOT_BOOTSTRAP" ] && [ "$(command -v go)" ] && export GOROOT_BOOTSTRAP=$(go env GOROOT)
+
+	if ! __gvm_is_bootstrap_compatible "$GO_NAME" "$GOROOT_BOOTSTRAP"; then
+		__gvm_ensure_bootstrap "$GO_NAME" || display_fatal "Failed to ensure bootstrap Go version"
+	fi
+
 	unset GOARCH && unset GOOS && unset GOPATH && unset GOBIN && unset GOROOT &&
 	export GOBIN=$GO_INSTALL_ROOT/bin &&
 	export PATH=$GOBIN:$PATH &&
@@ -196,8 +202,8 @@ download_binary() {
 		GVM_ARCH="s390x"
 	fi
 
-	SEMVER=$(extract_version $VERSION)
-	compare_version $SEMVER "1.4.3"
+	SEMVER=$(extract_version "$VERSION")
+	compare_version "$SEMVER" "1.4.3"
 	if [ $? -eq 2 ]; then
 		GO_BINARY_FILE=${VERSION}.${GVM_OS}-${GVM_ARCH}${GVM_OS_VERSION}.tar.gz
 	else