msvc-dev-cmd v1.8.0

* Workaround for repeated invocations

As noted in the comment, repeated invocations of this action might have
caused environment variables to overflow. This cute hack avoid this,
allowing to reconfigure environment.

* Note caveats in README

While this approach mostly works, I still have reservations so let's
leave some cautionary notes.

* Test repeated reconfiguration on CI

Well, let's build our "Hello, world!" four times, for four different
architectures, because why not.

.github/workflows/main.yml

@@ -18,13 +18,42 @@ jobs:
         uses: actions/checkout@v2
       - name: Download Internet
         run: npm install
-      - name: Enable Developer Command Prompt
+      - name: Enable Developer Command Prompt (amd64)
         uses: ./
-      - name: Compile and run some C code
+        with:
+          arch: amd64
+      - name: Compile and run some C code (amd64)
         shell: cmd
         run: |
           cl.exe hello.c
           hello.exe
+      - name: Enable Developer Command Prompt (amd64_x86)
+        uses: ./
+        with:
+          arch: amd64_x86
+      - name: Compile and run some C code (x86)
+        shell: cmd
+        run: |
+          cl.exe hello.c
+          hello.exe
+      - name: Enable Developer Command Prompt (amd64_arm)
+        uses: ./
+        with:
+          arch: amd64_arm
+      - name: Compile some C code (arm)
+        shell: cmd
+        run: |
+          cl.exe hello.c
+          dumpbin /headers hello.exe
+      - name: Enable Developer Command Prompt (amd64_arm64)
+        uses: ./
+        with:
+          arch: amd64_arm64
+      - name: Compile some C code (arm64)
+        shell: cmd
+        run: |
+          cl.exe hello.c
+          dumpbin /headers hello.exe
   audit:
     name: npm audit
     runs-on: windows-latest

.gitignore

@@ -1 +0,0 @@
-node_modules

README.md

@@ -8,14 +8,57 @@ This sets up the environment for compiling C/C++ code from command line.
 
 Supports Windows. Does nothing on Linux and macOS.
 
+## Example usage
+
+Basic usage for default compilation settings is like this:
+
+```yaml
+jobs:
+  test:
+    steps:
+      - uses: actions/checkout@v2
+      - uses: ilammy/msvc-dev-cmd@v1
+      - name: Build something requiring CL.EXE
+        run: |
+          cmake -G "NMake Makefiles" .
+          nmake
+      # ...
+```
+
+If you want something non-default,
+like using a specific version of Visual Studio,
+or cross-compling for a differen target,
+you will need to configure those settings via inputs:
+
+```yaml
+jobs:
+  test:
+    # Run a job for each of the specified target architectures:
+    strategy:
+      matrix:
+        arch:
+          - amd64
+          - amd64_x86
+          - amd64_arm64
+    steps:
+      - uses: actions/checkout@v2
+      - uses: ilammy/msvc-dev-cmd@v1
+        with:
+          arch: ${{ matrix.arch }}
+      - name: Build something requiring CL.EXE
+        run: |
+          cmake -G "NMake Makefiles" .
+          nmake
+      # ...
+```
+
 ## Inputs
 
 - `arch` – target architecture
   - native compilation:
     - `x64` (default) or its synonyms: `amd64`, `win64`
     - `x86` or its synonyms: `win32`
-  - cross-compilation: `x86_amd64`, `x86_arm`, `x86_arm64`,
-  	`amd64_x86`, `amd64_arm`, `amd64_arm64`
+  - cross-compilation: `x86_amd64`, `x86_arm`, `x86_arm64`, `amd64_x86`, `amd64_arm`, `amd64_arm64`
 - `sdk` – Windows SDK to use
   - do not specify to use the default SDK
   - or specify full Windows 10 SDK number (e.g, `10.0.10240.0`)
@@ -28,20 +71,64 @@ Supports Windows. Does nothing on Linux and macOS.
 - `uwp` – set `true` to build for Universal Windows Platform (i.e., for Windows Store)
 - `spectre` – set `true` to use Visual Studio libraries with [Spectre](https://meltdownattack.com) mitigations
 
-## Example usage
+## Caveats
+
+### Name conflicts with `shell: bash`
+
+Using `shell: bash` in Actions may shadow some of the paths added by MSVC.
+In particular, `link.exe` (Microsoft C linker) is prone to be shadowed by `/usr/bin/link` (GNU filesystem link tool).
+
+Unfortunately, this happens because GitHub Actions unconditionally *prepend* GNU paths when `shell: bash` is used,
+on top of any paths set by `msvc-dev-cmd`, every time at the start of each new step.
+Hence, there aren't many non-destructive options here.
+
+If you experience compilation errors where `link` complains about unreasonable command-line arguments,
+“extra operand *something-something*” – that's probably it.
+Recommended workaround is to remove `/usr/bin/link` if that interferes with your builds.
+If this is not acceptable, please file an issue, then we'll figure out something better.
+
+### Reconfiguration
+
+You can invoke `ilammy/msvc-dev-cmd` multiple times during your jobs with different inputs
+to reconfigure the environment for building with different settings
+(e.g., to target multiple architectures).
 
 ```yaml
 jobs:
-  test:
-    - uses: actions/checkout@v1
-    - uses: ilammy/msvc-dev-cmd@v1
-    - name: Build something requiring CL.EXE
-      run: |
-        cmake -G "NMake Makefiles" .
-        nmake
+  release:
+    steps:
+      # ...
+      - name: Configure build for amd64
+        uses: ilammy/msvc-dev-cmd@v1
+        with:
+          arch: amd64
+
+      - run: build # (for amd64)
+
+      - name: Configure build for x86
+        uses: ilammy/msvc-dev-cmd@v1
+        with:
+          arch: amd64_x86
+
+      - run: build # (for x86)
+
+      - name: Configure build for ARM64
+        uses: ilammy/msvc-dev-cmd@v1
+        with:
+          arch: amd64_arm64
+
+      - run: build # (for ARM64)
+
       # ...
 ```
 
+This mostly works but it's not really recommended
+since Developer Command Prompt was not meant for recursive reconfiguration.
+That said, if it does not work for you, please file an issue.
+
+Consider using [`strategy.matrix`](https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions#jobsjob_idstrategymatrix)
+to execute different build configuration in parallel, independent environments.
+
 ## License
 
 MIT, see [LICENSE](LICENSE).

index.js

@@ -11,19 +11,6 @@ const VERSIONS = ['2019', '2017']
 
 const VSWHERE_PATH = `${PROGRAM_FILES_X86}\\Microsoft Visual Studio\\Installer`
 
-const InterestingVariables = [
-    'INCLUDE',
-    'LIB',
-    'LIBPATH',
-    'VCINSTALLDIR',
-    'Path',
-    'Platform',
-    'VisualStudioVersion',
-    /^VCTools/,
-    /^VSCMD_/,
-    /^WindowsSDK/i,
-]
-
 function findWithVswhere(pattern) {
     try {
         let installationPath = child_process.execSync(`vswhere -products * -latest -prerelease -property installationPath`).toString().trim()
@@ -68,6 +55,21 @@ function findVcvarsall() {
     throw new Error('Microsoft Visual Studio not found')
 }
 
+function isPathVariable(name) {
+    const pathLikeVariables = ['PATH', 'INCLUDE', 'LIB', 'LIBPATH']
+    return pathLikeVariables.indexOf(name.toUpperCase()) != -1
+}
+
+function filterPathValue(path) {
+    let paths = path.split(';')
+    // Remove duplicates by keeping the first occurance and preserving order.
+    // This keeps path shadowing working as intended.
+    function unique(value, index, self) {
+        return self.indexOf(value) === index
+    }
+    return paths.filter(unique).join(';')
+}
+
 function main() {
     if (process.platform != 'win32') {
         core.info('This is not a Windows virtual environment, bye!')
@@ -111,15 +113,17 @@ function main() {
         args.push('-vcvars_spectre_libs=spectre')
     }
 
-    const command = `"${findVcvarsall()}" ${args.join(' ')} && set`
-    core.debug(`Running: ${command}`)
-    const environment = child_process.execSync(command, {shell: "cmd"}).toString().split('\r\n')
+    const vcvars = `"${findVcvarsall()}" ${args.join(' ')}`
+    core.debug(`vcvars command-line: ${vcvars}`)
+
+    const old_environment = child_process.execSync(`set`, {shell: "cmd"}).toString().split('\r\n')
+    const new_environment = child_process.execSync(`${vcvars} && set`, {shell: "cmd"}).toString().split('\r\n')
 
     // If vsvars.bat is given an incorrect command line, it will print out
     // an error and *still* exit successfully. Parse out errors from output
     // which don't look like environment variables, and fail if appropriate.
     var failed = false
-    for (let line of environment) {
+    for (let line of new_environment) {
         if (line.match(/^\[ERROR.*\]/)) {
             failed = true
             // Don't print this particular line which will be confusing in output.
@@ -133,15 +137,39 @@ function main() {
         throw new Error('invalid parameters')
     }
 
-    for (let string of environment) {
+    // Convert old environment lines into a dictionary for easier lookup.
+    let old_env_vars = {}
+    for (let string of old_environment) {
         const [name, value] = string.split('=')
-        for (let pattern of InterestingVariables) {
-            if (name.match(pattern)) {
-                core.exportVariable(name, value)
-                break
-            }
+        old_env_vars[name] = value
+    }
+
+    // Now look at the new environment and export everything that changed.
+    // These are the variables set by vsvars.bat. Also export everything
+    // that was not there during the first sweep: those are new variables.
+    core.startGroup('Environment variables')
+    for (let string of new_environment) {
+        // vsvars.bat likes to print some fluff at the beginning.
+        // Skip lines that don't look like environment variables.
+        if (!string.includes('=')) {
+            continue;
+        }
+        let [name, new_value] = string.split('=')
+        let old_value = old_env_vars[name]
+        // For new variables "old_value === undefined".
+        if (new_value !== old_value) {
+            core.info(`Setting ${name}`)
+            // Special case for a bunch of PATH-like variables: vcvarsall.bat
+            // just prepends its stuff without checking if its already there.
+            // This makes repeated invocations of this action fail after some
+            // point, when the environment variable overflows. Avoid that.
+            if (isPathVariable(name)) {
+                new_value = filterPathValue(new_value)
+            }
+            core.exportVariable(name, new_value)
         }
     }
+    core.endGroup()
 
     core.info(`Configured Developer Command Prompt`)
 }

package.json

@@ -1,6 +1,6 @@
 {
   "name": "msvc-dev-cmd",
-  "version": "1.1.1",
+  "version": "1.8.0",
   "description": "GitHub Action to setup Developer Command Prompt for Microsoft Visual C++",
   "main": "index.js",
   "scripts": {