diff --git a/checker/src/test/java/dev/cel/checker/CelIssueTest.java b/checker/src/test/java/dev/cel/checker/CelIssueTest.java
index e0d34fd0..a200a5fd 100644
--- a/checker/src/test/java/dev/cel/checker/CelIssueTest.java
+++ b/checker/src/test/java/dev/cel/checker/CelIssueTest.java
@@ -16,9 +16,7 @@
 
 import static com.google.common.truth.Truth.assertThat;
 
-import com.google.common.base.Joiner;
 import com.google.common.collect.ImmutableList;
-import com.google.common.collect.Iterables;
 import dev.cel.common.CelIssue;
 import dev.cel.common.CelSource;
 import org.junit.Test;
@@ -28,8 +26,6 @@
 @RunWith(JUnit4.class)
 public final class CelIssueTest {
 
-  private static final Joiner JOINER = Joiner.on('\n');
-
   @Test
   public void toDisplayString_narrow() throws Exception {
     CelSource source =
@@ -38,7 +34,7 @@ public void toDisplayString_narrow() throws Exception {
         ImmutableList.of(
             CelIssue.formatError(1, 1, "No such field"),
             CelIssue.formatError(2, 20, "Syntax error, missing paren"));
-    assertThat(JOINER.join(Iterables.transform(issues, error -> error.toDisplayString(source))))
+    assertThat(CelIssue.toDisplayString(issues, source))
         .isEqualTo(
             "ERROR: issues-test:1:2: No such field\n"
                 + " | a.b\n"
@@ -53,7 +49,7 @@ public void toDisplayString_wideAndNarrow() throws Exception {
     CelSource source = CelSource.newBuilder("你好吗\n我b很好\n").setDescription("issues-test").build();
     ImmutableList<CelIssue> issues =
         ImmutableList.of(CelIssue.formatError(2, 3, "Unexpected character '好'"));
-    assertThat(JOINER.join(Iterables.transform(issues, error -> error.toDisplayString(source))))
+    assertThat(CelIssue.toDisplayString(issues, source))
         .isEqualTo("ERROR: issues-test:2:4: Unexpected character '好'\n" + " | 我b很好\n" + " | ．.．＾");
   }
 
@@ -73,7 +69,8 @@ public void toDisplayString_emojis() throws Exception {
                     + " IDENTIFIER}"),
             CelIssue.formatError(1, 35, "Syntax error: token recognition error at: '😁'"),
             CelIssue.formatError(1, 36, "Syntax error: missing IDENTIFIER at '<EOF>'"));
-    assertThat(JOINER.join(Iterables.transform(issues, error -> error.toDisplayString(source))))
+
+    assertThat(CelIssue.toDisplayString(issues, source))
         .isEqualTo(
             "ERROR: issues-test:1:33: Syntax error: extraneous input 'in' expecting {'[', '{',"
                 + " '(', '.', '-', '!', 'true', 'false', 'null', NUM_FLOAT, NUM_INT, NUM_UINT,"
diff --git a/common/src/main/java/dev/cel/common/CelIssue.java b/common/src/main/java/dev/cel/common/CelIssue.java
index 1e3cdb58..2f507d5a 100644
--- a/common/src/main/java/dev/cel/common/CelIssue.java
+++ b/common/src/main/java/dev/cel/common/CelIssue.java
@@ -14,10 +14,14 @@
 
 package dev.cel.common;
 
+import static com.google.common.collect.ImmutableList.toImmutableList;
+
 import com.google.auto.value.AutoValue;
+import com.google.common.base.Joiner;
 import com.google.errorprone.annotations.CheckReturnValue;
 import com.google.errorprone.annotations.Immutable;
 import dev.cel.common.internal.SafeStringFormatter;
+import java.util.Collection;
 import java.util.Optional;
 import java.util.PrimitiveIterator;
 
@@ -28,6 +32,7 @@
 @Immutable
 @SuppressWarnings("UnicodeEscape") // Suppressed to distinguish half-width and full-width chars.
 public abstract class CelIssue {
+  private static final Joiner JOINER = Joiner.on('\n');
 
   /** Severity of a CelIssue. */
   public enum Severity {
@@ -73,6 +78,12 @@ public static CelIssue formatError(int line, int column, String message) {
   private static final char WIDE_DOT = '\uff0e';
   private static final char WIDE_HAT = '\uff3e';
 
+  /** Returns a human-readable error with all issues joined in a single string. */
+  public static String toDisplayString(Collection<CelIssue> issues, Source source) {
+    return JOINER.join(
+        issues.stream().map(iss -> iss.toDisplayString(source)).collect(toImmutableList()));
+  }
+
   /** Returns a string representing this error that is suitable for displaying to humans. */
   public String toDisplayString(Source source) {
     // Based onhttps://github.com/google/cel-go/blob/v0.5.1/common/error.go#L42.
diff --git a/common/src/main/java/dev/cel/common/CelValidationException.java b/common/src/main/java/dev/cel/common/CelValidationException.java
index ef136f8a..522706e8 100644
--- a/common/src/main/java/dev/cel/common/CelValidationException.java
+++ b/common/src/main/java/dev/cel/common/CelValidationException.java
@@ -15,15 +15,12 @@
 package dev.cel.common;
 
 import com.google.common.annotations.VisibleForTesting;
-import com.google.common.base.Joiner;
 import com.google.common.collect.ImmutableList;
-import com.google.common.collect.Iterables;
 import java.util.List;
 
 /** Base class for all checked exceptions explicitly thrown by the library during parsing. */
 public final class CelValidationException extends CelException {
 
-  private static final Joiner JOINER = Joiner.on('\n');
   // Truncates all errors beyond this limit in the message.
   private static final int MAX_ERRORS_TO_REPORT = 1000;
 
@@ -46,17 +43,14 @@ public CelValidationException(CelSource source, List<CelIssue> errors) {
 
   private static String safeJoinErrorMessage(CelSource source, List<CelIssue> errors) {
     if (errors.size() <= MAX_ERRORS_TO_REPORT) {
-      return JOINER.join(Iterables.transform(errors, error -> error.toDisplayString(source)));
+      return CelIssue.toDisplayString(errors, source);
     }
 
     List<CelIssue> truncatedErrors = errors.subList(0, MAX_ERRORS_TO_REPORT);
-    StringBuilder sb = new StringBuilder();
-    JOINER.appendTo(
-        sb, Iterables.transform(truncatedErrors, error -> error.toDisplayString(source)));
-    sb.append(
-        String.format("%n...and %d more errors (truncated)", errors.size() - MAX_ERRORS_TO_REPORT));
 
-    return sb.toString();
+    return CelIssue.toDisplayString(truncatedErrors, source)
+        + String.format(
+            "%n...and %d more errors (truncated)", errors.size() - MAX_ERRORS_TO_REPORT);
   }
 
   /** Returns the {@link CelSource} that was being validated. */
diff --git a/common/src/main/java/dev/cel/common/CelValidationResult.java b/common/src/main/java/dev/cel/common/CelValidationResult.java
index 3e52bc8e..61152c49 100644
--- a/common/src/main/java/dev/cel/common/CelValidationResult.java
+++ b/common/src/main/java/dev/cel/common/CelValidationResult.java
@@ -17,9 +17,7 @@
 import static com.google.common.collect.ImmutableList.toImmutableList;
 import static java.util.Comparator.comparing;
 
-import com.google.common.base.Joiner;
 import com.google.common.collect.ImmutableList;
-import com.google.common.collect.Iterables;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import com.google.errorprone.annotations.Immutable;
 import com.google.errorprone.annotations.InlineMe;
@@ -33,8 +31,6 @@
 @Immutable
 public final class CelValidationResult {
 
-  private static final Joiner JOINER = Joiner.on('\n');
-
   @SuppressWarnings("Immutable")
   private final @Nullable Throwable failure;
 
@@ -115,7 +111,7 @@ public ImmutableList<CelIssue> getAllIssues() {
 
   /** Convert all issues to a human-readable string. */
   public String getIssueString() {
-    return JOINER.join(Iterables.transform(issues, iss -> iss.toDisplayString(source)));
+    return CelIssue.toDisplayString(issues, source);
   }
 
   /**
@@ -131,7 +127,7 @@ public String getDebugString() {
 
   /** Convert the {@code CelIssue}s with {@code ERROR} severity to an error string. */
   public String getErrorString() {
-    return JOINER.join(Iterables.transform(getErrors(), error -> error.toDisplayString(source)));
+    return CelIssue.toDisplayString(getErrors(), source);
   }
 
   private static boolean issueIsError(CelIssue iss) {
diff --git a/policy/src/main/java/dev/cel/policy/BUILD.bazel b/policy/src/main/java/dev/cel/policy/BUILD.bazel
index 407ce2f4..c13bcf0c 100644
--- a/policy/src/main/java/dev/cel/policy/BUILD.bazel
+++ b/policy/src/main/java/dev/cel/policy/BUILD.bazel
@@ -109,7 +109,7 @@ java_library(
         ":source",
         ":validation_exception",
         ":value_string",
-        "//common:source",
+        "//common:compiler_common",
         "//common/internal",
         "@maven//:com_google_guava_guava",
         "@maven//:org_yaml_snakeyaml",
@@ -217,6 +217,7 @@ java_library(
         ":parser_context",
         ":source",
         ":validation_exception",
+        "//common:compiler_common",
         "//common/internal",
         "@maven//:com_google_guava_guava",
         "@maven//:org_yaml_snakeyaml",
@@ -265,7 +266,7 @@ java_library(
     deps = [
         ":policy",
         ":value_string",
-        "//common:source",
+        "//common:compiler_common",
     ],
 )
 
@@ -302,7 +303,6 @@ java_library(
         ":value_string",
         "//common",
         "//common:compiler_common",
-        "//common:source",
         "//common/internal",
         "@maven//:com_google_guava_guava",
         "@maven//:org_yaml_snakeyaml",
diff --git a/policy/src/main/java/dev/cel/policy/CelPolicyCompilerImpl.java b/policy/src/main/java/dev/cel/policy/CelPolicyCompilerImpl.java
index 4fb81f42..c2f1516d 100644
--- a/policy/src/main/java/dev/cel/policy/CelPolicyCompilerImpl.java
+++ b/policy/src/main/java/dev/cel/policy/CelPolicyCompilerImpl.java
@@ -15,9 +15,7 @@
 package dev.cel.policy;
 
 import static com.google.common.base.Preconditions.checkNotNull;
-import static com.google.common.collect.ImmutableList.toImmutableList;
 
-import com.google.common.base.Joiner;
 import com.google.common.collect.ImmutableList;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import dev.cel.bundle.Cel;
@@ -145,7 +143,6 @@ private static CelAbstractSyntaxTree newErrorAst() {
   }
 
   private static final class CompilerContext {
-    private static final Joiner JOINER = Joiner.on('\n');
     private final ArrayList<CelIssue> issues;
     private final ArrayList<CelVarDecl> newVariableDeclarations;
     private final CelPolicySource celPolicySource;
@@ -170,10 +167,7 @@ private boolean hasError() {
     }
 
     private String getIssueString() {
-      return JOINER.join(
-          issues.stream()
-              .map(iss -> iss.toDisplayString(celPolicySource))
-              .collect(toImmutableList()));
+      return CelIssue.toDisplayString(issues, celPolicySource);
     }
 
     private CompilerContext(CelPolicySource celPolicySource) {
diff --git a/policy/src/main/java/dev/cel/policy/CelPolicyYamlConfigParser.java b/policy/src/main/java/dev/cel/policy/CelPolicyYamlConfigParser.java
index 01dfc77b..d8955fe2 100644
--- a/policy/src/main/java/dev/cel/policy/CelPolicyYamlConfigParser.java
+++ b/policy/src/main/java/dev/cel/policy/CelPolicyYamlConfigParser.java
@@ -24,6 +24,7 @@
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
+import dev.cel.common.CelIssue;
 import dev.cel.common.internal.CelCodePointArray;
 import dev.cel.policy.CelPolicyConfig.ExtensionConfig;
 import dev.cel.policy.CelPolicyConfig.FunctionDecl;
@@ -339,8 +340,9 @@ private CelPolicyConfig parseYaml(String source, String description)
               .setPositionsMap(ctx.getIdToOffsetMap())
               .build();
 
-      if (ctx.hasError()) {
-        throw new CelPolicyValidationException(ctx.getIssueString(configSource));
+      if (!ctx.getIssues().isEmpty()) {
+        throw new CelPolicyValidationException(
+            CelIssue.toDisplayString(ctx.getIssues(), configSource));
       }
 
       return policyConfig.setConfigSource(configSource).build();
diff --git a/policy/src/main/java/dev/cel/policy/CelPolicyYamlParser.java b/policy/src/main/java/dev/cel/policy/CelPolicyYamlParser.java
index 5d36185a..0972451f 100644
--- a/policy/src/main/java/dev/cel/policy/CelPolicyYamlParser.java
+++ b/policy/src/main/java/dev/cel/policy/CelPolicyYamlParser.java
@@ -20,13 +20,14 @@
 import static dev.cel.policy.YamlHelper.assertYamlType;
 
 import com.google.common.collect.ImmutableSet;
-import dev.cel.common.Source;
+import dev.cel.common.CelIssue;
 import dev.cel.common.internal.CelCodePointArray;
 import dev.cel.policy.CelPolicy.Match;
 import dev.cel.policy.CelPolicy.Match.Result;
 import dev.cel.policy.CelPolicy.Variable;
 import dev.cel.policy.ParserContext.PolicyParserContext;
 import dev.cel.policy.YamlHelper.YamlNodeType;
+import java.util.List;
 import java.util.Map;
 import org.yaml.snakeyaml.nodes.MappingNode;
 import org.yaml.snakeyaml.nodes.Node;
@@ -76,8 +77,9 @@ private CelPolicy parseYaml() throws CelPolicyValidationException {
 
       CelPolicy celPolicy = parsePolicy(this, node);
 
-      if (ctx.hasError()) {
-        throw new CelPolicyValidationException(ctx.getIssueString(celPolicy.policySource()));
+      if (!ctx.getIssues().isEmpty()) {
+        throw new CelPolicyValidationException(
+            CelIssue.toDisplayString(ctx.getIssues(), celPolicy.policySource()));
       }
 
       return celPolicy;
@@ -296,13 +298,8 @@ public void reportError(long id, String message) {
     }
 
     @Override
-    public String getIssueString(Source source) {
-      return ctx.getIssueString(source);
-    }
-
-    @Override
-    public boolean hasError() {
-      return ctx.hasError();
+    public List<CelIssue> getIssues() {
+      return ctx.getIssues();
     }
 
     @Override
diff --git a/policy/src/main/java/dev/cel/policy/ParserContext.java b/policy/src/main/java/dev/cel/policy/ParserContext.java
index 385a022c..13b81641 100644
--- a/policy/src/main/java/dev/cel/policy/ParserContext.java
+++ b/policy/src/main/java/dev/cel/policy/ParserContext.java
@@ -14,10 +14,11 @@
 
 package dev.cel.policy;
 
-import dev.cel.common.Source;
+import dev.cel.common.CelIssue;
 import dev.cel.policy.CelPolicy.Match;
 import dev.cel.policy.CelPolicy.Rule;
 import dev.cel.policy.CelPolicy.Variable;
+import java.util.List;
 import java.util.Map;
 
 /**
@@ -40,9 +41,7 @@ public interface ParserContext<T> {
 
   void reportError(long id, String message);
 
-  String getIssueString(Source source);
-
-  boolean hasError();
+  List<CelIssue> getIssues();
 
   Map<Long, Integer> getIdToOffsetMap();
 
diff --git a/policy/src/main/java/dev/cel/policy/YamlParserContextImpl.java b/policy/src/main/java/dev/cel/policy/YamlParserContextImpl.java
index 613aca53..d84b9f83 100644
--- a/policy/src/main/java/dev/cel/policy/YamlParserContextImpl.java
+++ b/policy/src/main/java/dev/cel/policy/YamlParserContextImpl.java
@@ -14,18 +14,16 @@
 
 package dev.cel.policy;
 
-import static com.google.common.collect.ImmutableList.toImmutableList;
 import static dev.cel.policy.YamlHelper.ERROR;
 import static dev.cel.policy.YamlHelper.assertYamlType;
 
-import com.google.common.base.Joiner;
 import dev.cel.common.CelIssue;
 import dev.cel.common.CelSourceLocation;
-import dev.cel.common.Source;
 import dev.cel.common.internal.CelCodePointArray;
 import dev.cel.policy.YamlHelper.YamlNodeType;
 import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import org.yaml.snakeyaml.DumperOptions;
 import org.yaml.snakeyaml.nodes.Node;
@@ -34,8 +32,6 @@
 /** Package-private class to assist with storing policy parsing context. */
 final class YamlParserContextImpl implements ParserContext<Node> {
 
-  private static final Joiner JOINER = Joiner.on('\n');
-
   private final ArrayList<CelIssue> issues;
   private final HashMap<Long, CelSourceLocation> idToLocationMap;
   private final HashMap<Long, Integer> idToOffsetMap;
@@ -48,14 +44,8 @@ public void reportError(long id, String message) {
   }
 
   @Override
-  public String getIssueString(Source source) {
-    return JOINER.join(
-        issues.stream().map(iss -> iss.toDisplayString(source)).collect(toImmutableList()));
-  }
-
-  @Override
-  public boolean hasError() {
-    return !issues.isEmpty();
+  public List<CelIssue> getIssues() {
+    return issues;
   }
 
   @Override