fix: handle parsing variable expression in dockerfile (#337)

* fix: handle parsing variable expression in dockerfile * fix: use only one regex for all three cases (regular, positive, negative) of bash variables * fix: modify �rgumentExpression for optional braces * test: add tests for supporting variable expressions
devcontainers · Jan 3, 2023 · 338857f · 338857f
1 parent 0583b9c
commit 338857f
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diff --git a/src/spec-node/dockerfileUtils.ts b/src/spec-node/dockerfileUtils.ts
@@ -16,7 +16,8 @@ const parseFromLine = /FROM\s+(?<platform>--platform=\S+\s+)?"?(?<image>[^\s"]+)
 const fromStatement = /^\s*FROM\s+(?<platform>--platform=\S+\s+)?"?(?<image>[^\s"]+)"?(\s+[Aa][Ss]\s+(?<label>[^\s]+))?/m;
 const argEnvUserStatements = /^\s*(?<instruction>ARG|ENV|USER)\s+(?<name>[^\s=]+)([ =]+("(?<value1>\S+)"|(?<value2>\S+)))?/gm;
 const directives = /^\s*#\s*(?<name>\S+)\s*=\s*(?<value>.+)/;
-const variables = /\$\{?(?<variable>[a-zA-Z0-9_]+)\}?/g;
+
+const argumentExpression = /\$\{?(?<variable>[^:\}]+)(?<isVarExp>:(?<option>-|\+)(?<word>[^\}]+))?\}?/g;
 
 export interface Dockerfile {
 	preamble: {
@@ -138,11 +139,29 @@ function extractInstructions(stageStr: string) {
 		});
 }
 
-function replaceVariables(dockerfile: Dockerfile, buildArgs: Record<string, string>, baseImageEnv: Record<string, string>, str: string, stage: { from?: From; instructions: Instruction[] }, beforeInstructionIndex: number) {
-	return [...str.matchAll(variables)]
+function getExpressionValue(option: string, isSet: boolean, word: string, value: string) {
+	const operations: Record<string, Function> = { 
+		'-': (isSet: boolean, word: string, value: string) => isSet ? value : word,
+		'+': (isSet: boolean, word: string, value: string) => isSet ? word : value,
+	};
+
+	return operations[option](isSet, word, value).replace(/^['"]|['"]$/g, ''); // remove quotes from start and end of the string
+}
+
+function replaceVariables(dockerfile: Dockerfile, buildArgs: Record<string, string>, baseImageEnv: Record<string, string>, str: string, stage: { from?: From; instructions: Instruction[] }, beforeInstructionIndex: number) {			
+	return [...str.matchAll(argumentExpression)]
 		.map(match => {
 			const variable = match.groups!.variable;
-			const value = findValue(dockerfile, buildArgs, baseImageEnv, variable, stage, beforeInstructionIndex) || '';
+			const isVarExp = match.groups!.isVarExp ? true : false;
+			let value = findValue(dockerfile, buildArgs, baseImageEnv, variable, stage, beforeInstructionIndex) || '';
+			if (isVarExp) {
+				// Handle replacing variable expressions (${var:+word}) if they exist
+				const option = match.groups!.option;
+				const word = match.groups!.word;
+				const isSet = value !== '';
+				value = getExpressionValue(option, isSet, word, value);
+			}
+
 			return {
 				begin: match.index!,
 				end: match.index! + match[0].length,

diff --git a/src/test/dockerfileUtils.test.ts b/src/test/dockerfileUtils.test.ts
@@ -257,6 +257,56 @@ FROM "\${BASE_IMAGE}"
         const image = findBaseImage(extracted, {}, undefined);
         assert.strictEqual(image, 'ubuntu:latest');
     });
+
+    describe('Variable substitution', () => {
+        it('Positive variable expression with value specified', async () => {
+            const dockerfile = `
+ARG cloud
+FROM \${cloud:+mcr.microsoft.com/}azure-cli:latest
+`;
+            const extracted = extractDockerfile(dockerfile);
+            assert.strictEqual(extracted.stages.length, 1);
+            const image = findBaseImage(extracted, {
+                'cloud': 'true'
+            }, undefined);
+            assert.strictEqual(image, 'mcr.microsoft.com/azure-cli:latest');
+        });
+
+        it('Positive variable expression with no value specified', async () => {
+            const dockerfile = `
+ARG cloud
+FROM \${cloud:+mcr.microsoft.com/}azure-cli:latest
+`;
+            const extracted = extractDockerfile(dockerfile);
+            assert.strictEqual(extracted.stages.length, 1);
+            const image = findBaseImage(extracted, {}, undefined);
+            assert.strictEqual(image, 'azure-cli:latest');
+        });
+
+        it('Negative variable expression with value specified', async () => {
+            const dockerfile = `
+ARG cloud
+FROM \${cloud:-mcr.microsoft.com/}azure-cli:latest
+`;
+            const extracted = extractDockerfile(dockerfile);
+            assert.strictEqual(extracted.stages.length, 1);
+            const image = findBaseImage(extracted, {
+                'cloud': 'ghcr.io/'
+            }, undefined);
+            assert.strictEqual(image, 'ghcr.io/azure-cli:latest');
+        });
+
+        it('Negative variable expression with no value specified', async () => {
+            const dockerfile = `
+ARG cloud
+FROM \${cloud:-mcr.microsoft.com/}azure-cli:latest
+`;
+            const extracted = extractDockerfile(dockerfile);
+            assert.strictEqual(extracted.stages.length, 1);
+            const image = findBaseImage(extracted, {}, undefined);
+            assert.strictEqual(image, 'mcr.microsoft.com/azure-cli:latest');
+        });
+    });
 });
 
 describe('findUserStatement', () => {