Avoid infinite dry-run loop with automake projects

The top makefile in projects that use autotools and automake contains a
rule to remake the makefile itself when the configuration changes
(configure.ac).

Even when dry-running, GNU make regenerates the makefile, in a bid to
generate a 'correct' dry-run output.

VScode needs to add --always-make in order to get a complete view of the
dry-run. Without it, it would only get the commands needed for outdated
targets.

These two behaviours combined cause a naive 'make --dry-run --always-make'
to continuously remake the Makefile. In order to avoid this infinite loop,
make must be instructed as in the "Remaking Makefiles" man page, to
avoid remaking the makefile. This is done by adding two options:
  --assume-old=Makefile, and
  Makefile (ie, target).

Make requires the Makefile to be explicitly specified as target, otherwise
it ignores the --assume-old=Makefile option.

Furthermore, Makefiles generated by automake cause the top invocation to
be a recursive sub-make invocation. On recursive makes, make itself calls
submake without passing the --assume-old option, thus breaking the combo
required for the sub-make to avoid remaking the makefile. As a result,
automake Makefiles need one more workaround. The --assume-old option must
be manually passed to sub-make via the AM_MAKEFLAGS, which is always
appended to sub-make's command line.

This commit implements the above incantation to enable automake Makefiles
to be dry-run without an infinite loop.

Additionally, the makefilePath, makeDirectory, updatedMakefilePath and
updatedMakeDirectory variables are made to store the respective setting,
rather then re-purposing them to store the corresponding resolved,
absolute paths. makefilePath cannot be undefined because for dry-running
the name of the makefile must always be supplied on the make commandline.

Author: drok

package.nls.json

@@ -23,7 +23,7 @@
    "makefile-tools.configuration.makefile.makePath.description": "The path to the make tool",
    "makefile-tools.configuration.makefile.configurations.description": "The user defined makefile configurations",
    "makefile-tools.configuration.makefile.configurations.name.description": "The name of the makefile configuration",
-   "makefile-tools.configuration.makefile.configurations.makefilePath.description": "File path to the makefile",
+   "makefile-tools.configuration.makefile.configurations.makefilePath.description": "File path to the makefile. Defaults to 'Makefile'",
    "makefile-tools.configuration.makefile.configurations.makePath.description": "File path to the make command",
    "makefile-tools.configuration.makefile.configurations.makeDirectory.description": "Folder path passed to make via the -C switch",
    "makefile-tools.configuration.makefile.configurations.makeArgs.description": "Arguments to pass to the make command",

src/configuration.ts

@@ -194,35 +194,37 @@ async function readMakePath(): Promise<void> {
     }
 }
 
-let makefilePath: string | undefined;
-export function getMakefilePath(): string | undefined { return makefilePath; }
-export function setMakefilePath(path: string): void { makefilePath = path; }
+let makefilePath: string = "Makefile";
+export function getMakefilePath(): string { return makefilePath; }
+export function setMakefilePath(path: string = "Makefile"): void { makefilePath = path; }
 // Read the full path to the makefile if defined in settings.
 // It represents a default to look for if no other makefile is already provided
 // in makefile.configurations.makefilePath.
 // TODO: validate and integrate with "-f [Makefile]" passed in makefile.configurations.makeArgs.
 async function readMakefilePath(): Promise<void> {
-    makefilePath = await util.getExpandedSetting<string>("makefilePath");
-    if (!makefilePath) {
+    let makefilePathSetting: string | undefined = await util.getExpandedSetting<string>("makefilePath");
+    if (!makefilePathSetting) {
         logger.message("No path to the makefile is defined in the settings file.");
+        setMakefilePath();
     } else {
-        makefilePath = util.resolvePathToRoot(makefilePath);
+        setMakefilePath(makefilePathSetting);
     }
 }
 
 let makeDirectory: string | undefined;
 export function getMakeDirectory(): string | undefined { return makeDirectory; }
-export function setMakeDirectory(dir: string): void { makeDirectory = dir; }
+export function setMakeDirectory(dir: string = ''): void { makeDirectory = dir; }
 // Read the make working directory path if defined in settings.
 // It represents a default to look for if no other makeDirectory is already provided
 // in makefile.configurations.makeDirectory.
 // TODO: validate and integrate with "-C [DIR_PATH]" passed in makefile.configurations.makeArgs.
 async function readMakeDirectory(): Promise<void> {
-    makeDirectory = await util.getExpandedSetting<string>("makeDirectory");
-    if (!makeDirectory) {
+    let makeDirectorySetting: string | undefined = await util.getExpandedSetting<string>("makeDirectory");
+    if (!makeDirectorySetting) {
         logger.message("No folder path to the makefile is defined in the settings file.");
+        setMakeDirectory();
     } else {
-      makeDirectory = util.resolvePathToRoot(makeDirectory);
+        setMakeDirectory(makeDirectorySetting);
     }
 }
 
@@ -806,7 +808,7 @@ export async function getCommandForConfiguration(configuration: string | undefin
             }
         }
 
-        if (!util.checkFileExistsSync(configurationMakefile)) {
+        if (!util.checkFileExistsSync(util.resolvePathToRoot(configurationMakefile))) {
             logger.message("The makefile entry point was not found. " +
                 "Make sure it exists at the location defined by makefile.makefilePath, makefile.configurations[].makefilePath, " +
                 "makefile.makeDirectory, makefile.configurations[].makeDirectory" +
@@ -1305,9 +1307,6 @@ export async function initFromSettings(activation: boolean = false): Promise<voi
 
             subKey = "makefilePath";
             let updatedMakefilePath : string | undefined = await util.getExpandedSetting<string>(subKey);
-            if (updatedMakefilePath) {
-                updatedMakefilePath = util.resolvePathToRoot(updatedMakefilePath);
-            }
             if (updatedMakefilePath !== makefilePath) {
                 // A change in makefile.makefilePath should trigger an IntelliSense update
                 // only if the extension is not currently reading from a build log.
@@ -1319,9 +1318,6 @@ export async function initFromSettings(activation: boolean = false): Promise<voi
 
             subKey = "makeDirectory";
             let updatedMakeDirectory : string | undefined = await util.getExpandedSetting<string>(subKey);
-            if (updatedMakeDirectory) {
-                updatedMakeDirectory = util.resolvePathToRoot(updatedMakeDirectory);
-            }
             if (updatedMakeDirectory !== makeDirectory) {
                 // A change in makefile.makeDirectory should trigger an IntelliSense update
                 // only if the extension is not currently reading from a build log.

src/make.ts

@@ -467,7 +467,11 @@ export async function generateParseContent(progress: vscode.Progress<{}>,
         makeArgs.push("--question");
         logger.messageNoCR("Generating targets information with command: ");
     } else {
+        const makefilePath :string = configuration.getMakefilePath();
         makeArgs.push("--dry-run");
+        makeArgs.push(`--assume-old=${makefilePath}`);
+        makeArgs.push(makefilePath);
+        makeArgs.push("AM_MAKEFLAGS=--assume-old=Makefile Makefile");
 
         // If this is not a clean configure, remove --always-make from the arguments list.
         // We need to have --always-make in makefile.dryrunSwitches and remove it for not clean configure