Automatic version switching in powershell

doc/AUTO.md

@@ -0,0 +1,11 @@
+# AUTO Command - Node Version Switcher
+```
+nvs auto
+nvs auto on
+nvs auto off
+```
+When invoked with no parameters, `nvs auto` searches for the nearest `.node-version` file in the current directory or parent directories. If found, the version specified in the file is then added (if necessary) and used. If no `.node-version` file is found, then the default (linked) version, if any, is used.
+
+The `nvs auto on` command enables automatic switching as needed whenever the current shell's working directory changes; `nvs auto off` disables automatic switching in the current shell. (This feature is not supported in Windows Command Prompt.)
+
+A `.node-version` file must contain a single line with a valid NVS version string. A version string consists of a semantic version number, optionally preceded by a remote name, optionally followed by a processor architecture or bitness ("x86", "x64", "32", "64"), separated by slashes. Version labels ("lts", "latest") are not supported for use with the USE command. Examples: "4.6.0", "6.3.1/x86", "node/6.7.0/x64"

lib/addRemove.js

@@ -277,15 +277,15 @@ function getArchiveFileNameAndUri(version, remoteUri) {
 function remove(version) {
     let result = [];
 
+    // Unlink this version if it is linked.
+    result = result.concat(nvsLink.unlink(version));
+
     let currentVersion = nvsUse.getCurrentVersion();
     if (currentVersion && nvsVersion.equal(currentVersion, version)) {
         // The specified version is currently in use. Remove it from the PATH.
         result = result.concat(nvsUse.use(null));
     }
 
-    // Unlink this version if it is linked.
-    result = result.concat(nvsLink.unlink(version));
-
     // Remove all contents of the version directory,
     // along with parent directories if they are empty.
     let versionDir = nvsUse.getVersionDir(version);

lib/auto.js

@@ -0,0 +1,89 @@
+/* global settings */
+let fs = require('fs');  // Non-const enables test mocking
+const os = require('os');
+const path = require('path');
+const Error = require('./error');
+
+const nvsVersion = require('./version');
+let nvsUse = require('./use');  // Non-const enables test mocking
+let nvsAddRemove = require('./addRemove');  // Non-const enables test mocking
+
+/**
+ * Searches for the nearest `.node-version` file in the current directory or parent directories.
+ * If found, the version specified in the file is then added (if necessary) and used. If no
+ * `.node-version` file is found, then the default (linked) version, if any, is used.
+ */
+function autoSwitchAsync(cwd) {
+    let version = null;
+    let dir = cwd || process.cwd();
+    while (dir) {
+        let versionFile = path.join(dir, '.node-version');
+        try {
+            let versionString = fs.readFileSync(versionFile, 'utf8').trim();
+            try {
+                version = nvsVersion.parse(versionString);
+            } catch (e) {
+                throw new Error('Failed to parse version in file: ' + versionFile, e);
+            }
+        } catch (e) {
+            Error.throwIfNot(Error.ENOENT, e, 'Failed to read file: ' + versionFile);
+        }
+
+        let parentDir = path.dirname(dir);
+        dir = (parentDir !== dir ? parentDir : null);
+    }
+
+
+    if (version) {
+        let binPath = nvsUse.getVersionBinary(version);
+        if (!binPath) {
+            let versionString =
+                version.remoteName + '/' + version.semanticVersion + '/' + version.arch;
+            console.log('Adding: ' + versionString);
+
+            return nvsAddRemove.addAsync(version).then(() => {
+                return nvsUse.use(version);
+            });
+        }
+    }
+
+    return Promise.resolve(nvsUse.use(version));
+}
+
+/**
+ * Enables or disables automatic version switching based on the presence of a
+ * .node-version file in the current shell directory or a parent directory.
+ * (This functionality requires support from the bootstrap shell script.)
+ *
+ * @param {any} enable
+ */
+function enableAutoSwitch(enable) {
+    if (/\.cmd/i.test(process.env['NVS_POSTSCRIPT'])) {
+        throw new Error('Automatic switching is not supported from a Windows Command Prompt.' +
+            os.EOL + 'Use PowerShell instead.');
+    }
+
+    let psScriptFile = path.join(path.resolve(__dirname, '..'), 'nvs.ps1');
+    let shScriptFile = path.join(path.resolve(__dirname, '..'), 'nvs.sh');
+
+    require('./postScript').generate(null, {
+        '.PS1': [
+            // Patch the function that is invoked every time PowerShell shows a prompt.
+            // Export the function from the script using a dynamic module; this
+            // does NOT require the script to be sourced.
+            'if (-not $env:NVS_ORIGINAL_PROMPT) { $env:NVS_ORIGINAL_PROMPT = prompt }',
+            'New-Module -Script {',
+            enable
+                ? 'function prompt { . "' + psScriptFile + '" "prompt" }'
+                : 'function prompt { Invoke-Expression $env:NVS_ORIGINAL_PROMPT }',
+            'Export-ModuleMember -Function prompt',
+            '} > $null',
+        ],
+        '.SH': null // TODO: define cd(), pushd(), popd() functions
+    });
+}
+
+module.exports = {
+    autoSwitchAsync,
+    enableAutoSwitch,
+};

lib/help.js

@@ -40,6 +40,9 @@ function help(topic) {
         'nvs use [version]              ' + (canUpdateEnv
             ? 'Use a node version in the current shell'
             : '(Not available, source nvs.sh instead)'),
+        'nvs auto [on/off]              ' + (canUpdateEnv
+            ? 'Automatically switch based on cwd'
+            : '(Not available, source nvs.sh instead)'),
         'nvs run <ver> <js> [args...]   Run a script using a node version',
         'nvs exec <ver> <exe> [args...] Run an executable using a node version',
         'nvs which [version]            Show the path to a node version binary',

lib/link.js

@@ -109,6 +109,7 @@ function unlink(version) {
 
     let result = [];
     let linkPath = nvsUse.getLinkPath();
+    let currentVersion = nvsUse.getCurrentVersion();
 
     nvsInstall = nvsInstall || require('./install');
     if (nvsInstall.isInSystemDirectory()) {
@@ -129,6 +130,12 @@ function unlink(version) {
         Error.throwIfNot(Error.ENOENT, e, 'Failed to remove symbolic link: ' + linkPath);
     }
 
+    if (currentVersion && !nvsUse.getVersionBinary(currentVersion)) {
+        currentVersion = null;
+    }
+
+    result = result.concat(nvsUse.use(currentVersion));
+
     return result;
 }
 

lib/main.js

@@ -169,6 +169,30 @@ function doCommand(args) {
             }
             return require('./link').unlink(version);
 
+        case 'auto':
+            if (help) return help('auto');
+            if (!canUpdateEnv) {
+                throw new Error(
+                    'The \'auto\' command is not available when ' +
+                    'invoking this script as an' + os.EOL +
+                    'executable. To enable PATH updates, source ' +
+                    'nvs.sh from your shell instead.');
+            }
+            if (!args[1]) {
+                return require('./auto').autoSwitchAsync();
+            } else switch (args[1].toLowerCase()) {
+                case 'at':
+                    return require('./auto').autoSwitchAsync(args[2]);
+                case 'on':
+                case 'enable':
+                    return require('./auto').enableAutoSwitch(true);
+                case 'off':
+                case 'disable':
+                    return require('./auto').enableAutoSwitch(false);
+                default:
+                    return require('./help')('auto');
+            }
+
         case 'use':
             if (help) return help('use');
             if (!canUpdateEnv) {

lib/postScript.js

@@ -9,7 +9,7 @@ const canUpdateEnv = !process.env['NVS_EXECUTE'];
  * The NVS shim shell scripts take care of invoking the generated script and
  * deleting it afterward.
  */
-function generate(exportVars) {
+function generate(exportVars, additionalLines) {
     if (!canUpdateEnv) {
         // Don't throw an error; this allows commands like uninstall to
         // work even when they can't update PATH.
@@ -18,40 +18,44 @@ function generate(exportVars) {
     }
 
     let envVars = Object.keys(exportVars || {});
-    if (envVars.length > 0) {
-        let postScriptLines = [];
-        let postScriptFile = process.env['NVS_POSTSCRIPT'];
-        if (!postScriptFile) {
-            throw new Error('NVS_POSTSCRIPT environment variable not set.');
-        }
+    let postScriptLines = [];
+    let postScriptFile = process.env['NVS_POSTSCRIPT'];
+    if (!postScriptFile) {
+        throw new Error('NVS_POSTSCRIPT environment variable not set.');
+    }
+
+    let postScriptExtension = path.extname(postScriptFile).toUpperCase();
+    if (postScriptExtension === '.CMD') {
+        envVars.forEach(envVar => {
+            if (exportVars[envVar] !== null) {
+                postScriptLines.push('SET ' + envVar + '=' + exportVars[envVar]);
+            } else {
+                postScriptLines.push('SET ' + envVar + '=');
+            }
+        });
+    } else if (postScriptExtension === '.PS1') {
+        envVars.forEach(envVar => {
+            if (exportVars[envVar] !== null) {
+                postScriptLines.push('$env:' + envVar + '="' + exportVars[envVar] + '"');
+            } else {
+                postScriptLines.push('Remove-Item env:' + envVar + ' -ErrorAction SilentlyContinue');
+            }
+        });
+    } else if (postScriptExtension === '.SH') {
+        envVars.forEach(envVar => {
+            if (exportVars[envVar] !== null) {
+                postScriptLines.push('export ' + envVar + '="' + exportVars[envVar] + '"');
+            } else {
+                postScriptLines.push('unset ' + envVar);
+            }
+        });
+    }
 
-        let postScriptExtension = path.extname(postScriptFile).toUpperCase();
-        if (postScriptExtension === '.CMD') {
-            envVars.forEach(envVar => {
-                if (exportVars[envVar] !== null) {
-                    postScriptLines.push('SET ' + envVar + '=' + exportVars[envVar]);
-                } else {
-                    postScriptLines.push('SET ' + envVar + '=');
-                }
-            });
-        } else if (postScriptExtension === '.PS1') {
-            envVars.forEach(envVar => {
-                if (exportVars[envVar] !== null) {
-                    postScriptLines.push('$env:' + envVar + '="' + exportVars[envVar] + '"');
-                } else {
-                    postScriptLines.push('Remove-Item env:' + envVar + ' -ErrorAction SilentlyContinue');
-                }
-            });
-        } else if (postScriptExtension === '.SH') {
-            envVars.forEach(envVar => {
-                if (exportVars[envVar] !== null) {
-                    postScriptLines.push('export ' + envVar + '="' + exportVars[envVar] + '"');
-                } else {
-                    postScriptLines.push('unset ' + envVar);
-                }
-            });
-        }
+    if (additionalLines && additionalLines[postScriptExtension]) {
+        postScriptLines = postScriptLines.concat(additionalLines[postScriptExtension]);
+    }
 
+    if (postScriptLines.length > 0) {
         fs.writeFileSync(postScriptFile, postScriptLines.join(os.EOL) + os.EOL);
     }
 }

lib/use.js

@@ -109,7 +109,7 @@ function use(version, skipUpdateShellEnv) {
             let versionString = pathEntry.substr(settings.home.length);
             if (versionString === linkName) {
                 nvsLink = nvsLink || require('./link');
-                previousVersion = nvsLink.getLinkedVersion();
+                previousVersion = nvsLink.getLinkedVersion() || {};
             } else {
                 if (path.sep === '\\') {
                     versionString = versionString.replace(/\\/g, '/');
@@ -136,9 +136,20 @@ function use(version, skipUpdateShellEnv) {
         }
     }
 
+    let versionDir = null;
     if (version) {
         // Insert the requested version at the front of the PATH.
-        let versionDir = getVersionDir(version);
+        versionDir = getVersionDir(version);
+    } else {
+        // Insert the default version (if any) at the front of the path.
+        nvsLink = nvsLink || require('./link');
+        let defaultVersion = nvsLink.getLinkedVersion();
+        if (defaultVersion) {
+            versionDir = path.join(settings.home, 'default');
+        }
+    }
+
+    if (versionDir) {
         if (!isWindows) {
             versionDir = path.join(versionDir, 'bin');
         } else if (versionDir.endsWith(path.sep)) {

lib/version.js

@@ -64,7 +64,7 @@ function parse(versionString, requireFull) {
     }
 
     if (label && label !== 'latest' && label !== 'lts' && !label.startsWith('lts-')) {
-        throw new Error('Invalid version label: ' + label);
+        throw new Error('Invalid version label or alias: ' + label);
     }
 
     if (!arch) {

nvs.ps1

@@ -2,6 +2,7 @@
 # Bootstraps node.exe if necessary, then forwards arguments to the main nvs.js script.
 
 $scriptDir = Split-Path $MyInvocation.MyCommand.Path
+$mainScript = Join-Path $scriptDir "lib\main.js"
 
 # The NVS_HOME path may be overridden in the environment.
 if (-not $env:NVS_HOME) {
@@ -56,10 +57,39 @@ if (-not (Test-Path $bootstrapNodePath)) {
     }
 }
 
-# Forward the args to the main JavaScript file.
-$mainScript = Join-Path $scriptDir "lib\main.js"
-. "$bootstrapNodePath" "$mainScript" @args
-$exitCode = $LastExitCode
+# Check if this script was invoked as a PS prompt function that enables auto-switching.
+if ($args -eq "prompt") {
+    Invoke-Expression $env:NVS_ORIGINAL_PROMPT
+
+    # Find the nearest .node-version file in current or parent directories
+    for ($parentDir = $pwd.Path; $parentDir; $parentDir = Split-Path $parentDir) {
+        if (Test-Path (Join-Path $parentDir ".node-version") -PathType Leaf) { break }
+    }
+
+    # If it's still the same as the last auto-switched directory, then there's nothing to do.
+    if ([string]$parentDir -eq [string]$env:NVS_AUTO_DIRECTORY) {
+        exit 0
+    }
+    $env:NVS_AUTO_DIRECTORY = $parentDir
+
+    # Output needs to be redirected to Write-Host, because stdout is ignored by prompt.
+    # Process a byte at a time so that output like progress bars is real-time.
+    $startInfo = New-Object System.Diagnostics.ProcessStartInfo $bootstrapNodePath
+    $startInfo.Arguments = ($mainScript, "auto", "at", $pwd.Path)
+    $startInfo.UseShellExecute = $false
+    $startInfo.RedirectStandardOutput = $true
+    $proc = [System.Diagnostics.Process]::Start($startInfo)
+    while (($b = $proc.StandardOutput.Read()) -ne -1) {
+        Write-Host -NoNewline ([char]$b)
+    }
+    $proc.WaitForExit
+    $exitCode = $proc.ExitCode
+}
+else {
+    # Forward the args to the main JavaScript file.
+    . "$bootstrapNodePath" "$mainScript" @args
+    $exitCode = $LastExitCode
+}
 
 # Call the post-invocation script if it is present, then delete it.
 # This allows the invocation to potentially modify the caller's environment (e.g. PATH).
@@ -69,5 +99,4 @@ if (Test-Path $env:NVS_POSTSCRIPT) {
 }
 
 $env:NVS_POSTSCRIPT = $null
-
 exit $exitCode